By using a module parameter named acpi.supported_rev=<value>, the BIOS may be told a different supported ACPI revision compared to the default (which currently is 5, but will be modified to 2 when the revert of b1ef29725865 is reverted).

Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net --- Documentation/kernel-parameters.txt | 14 ++++++++++++++ drivers/acpi/osl.c | 16 ++++++++++++++++ 2 files changed, 30 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 61ab162..75f1f8e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -335,6 +335,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted. to assume that this machine's pmtimer latches its value and always returns good values.

+ acpi.rev= [HW,ACPI] + Tell ACPI BIOS the supported ACPI REV + Format: <int> in range 0..5 + Up to and including Linux v4.1, the BIOS was told which + ACPI revision the ACPICA subsystem in Linux actually + supports (which was 5 at the time); from v4.2 on, this + value will be set statically to 2 to match the behavior + of other ACPI implementations. As some BIOS may operate + differently depending on which value _REV is set to, this + parameter offers the capability to specify what to export + to the BIOS. Note that such changes in the behavior of + the BIOS may only be visible after cold booting the + system with this parameter _twice_. + acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low }

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index db14a66..caa52f7 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -538,6 +538,11 @@ acpi_os_get_physical_address(void *virt, acpi_physical_address * phys)

static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN];

+/* acpi_supported_rev is 0 in case of no override; overrides are limited to + * values between 1 to 5. To simplify casting, use an unsigned long */ +static unsigned long acpi_supported_rev; +module_param_named(rev, acpi_supported_rev, ulong, 0); + acpi_status acpi_os_predefined_override(const struct acpi_predefined_names *init_val, char **new_val) @@ -552,6 +557,17 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val, *new_val = acpi_os_name; }

+ if (!memcmp(init_val->name, "_REV", 4) && (acpi_supported_rev > 0)) { + if (acpi_supported_rev <= 5) { + printk(KERN_INFO PREFIX + "Overriding _REV definition to %lu\n", + acpi_supported_rev); + *new_val = (char *) acpi_supported_rev; + } else + printk(KERN_INFO PREFIX + "_REV override must be between 1 to 5"); + } + return AE_OK; }

Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net --- Documentation/kernel-parameters.txt | 62 ++++++++++++++++++------------------- 1 file changed, 31 insertions(+), 31 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 75f1f8e..d6db165 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -179,11 +179,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.

See also Documentation/power/runtime_pm.txt, pci=noacpi

- acpi_rsdp= [ACPI,EFI,KEXEC] - Pass the RSDP address to the kernel, mostly used - on machines running EFI runtime service to boot the - second kernel for kdump. - acpi_apic_instance= [ACPI, IOAPIC] Format: <int> 2: use 2nd APIC table, if available @@ -197,6 +192,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. (e.g. thinkpad_acpi, sony_acpi, etc.) instead of the ACPI video.ko driver.

+ acpica_no_return_repair [HW, ACPI] + Disable AML predefined validation mechanism + This mechanism can repair the evaluation result to make + the return objects more ACPI specification compliant. + This option is useful for developers to identify the + root cause of an AML interpreter issue when the issue + has something to do with the repair mechanism. + acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] acpi.debug_level= [HW,ACPI,ACPI_DEBUG] Format: <int> @@ -225,6 +228,22 @@ bytes respectively. Such letter suffixes can also be entirely omitted. unusable. The "log_buf_len" parameter may be useful if you need to capture more output.

+ acpi_enforce_resources= [ACPI] + { strict | lax | no } + Check for resource conflicts between native drivers + and ACPI OperationRegions (SystemIO and SystemMemory + only). IO ports and memory declared in ACPI might be + used by the ACPI subsystem in arbitrary AML code and + can interfere with legacy drivers. + strict (default): access to resources claimed by ACPI + is denied; legacy drivers trying to access reserved + resources will fail to bind to device using them. + lax: access to resources claimed by ACPI is allowed; + legacy drivers trying to access reserved resources + will bind successfully but a warning message is logged. + no: ACPI OperationRegions are not marked as reserved, + no further checks are performed. + acpi_force_table_verification [HW,ACPI] Enable table checksum verification during early stage. By default, this is disabled due to x86 early mapping @@ -253,6 +272,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. This feature is enabled by default. This option allows to turn off the feature.

+ acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump + kernels. + acpi_no_static_ssdt [HW,ACPI] Disable installation of static SSDTs at early boot time By default, SSDTs contained in the RSDT/XSDT will be @@ -263,13 +285,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. dynamic table installation which will install SSDT tables to /sys/firmware/acpi/tables/dynamic.

- acpica_no_return_repair [HW, ACPI] - Disable AML predefined validation mechanism - This mechanism can repair the evaluation result to make - the return objects more ACPI specification compliant. - This option is useful for developers to identify the - root cause of an AML interpreter issue when the issue - has something to do with the repair mechanism. + acpi_rsdp= [ACPI,EFI,KEXEC] + Pass the RSDP address to the kernel, mostly used + on machines running EFI runtime service to boot the + second kernel for kdump.

acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS Format: To spoof as Windows 98: ="Microsoft Windows" @@ -379,25 +398,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Use timer override. For some broken Nvidia NF5 boards that require a timer override, but don't have HPET

- acpi_enforce_resources= [ACPI] - { strict | lax | no } - Check for resource conflicts between native drivers - and ACPI OperationRegions (SystemIO and SystemMemory - only). IO ports and memory declared in ACPI might be - used by the ACPI subsystem in arbitrary AML code and - can interfere with legacy drivers. - strict (default): access to resources claimed by ACPI - is denied; legacy drivers trying to access reserved - resources will fail to bind to device using them. - lax: access to resources claimed by ACPI is allowed; - legacy drivers trying to access reserved resources - will bind successfully but a warning message is logged. - no: ACPI OperationRegions are not marked as reserved, - no further checks are performed. - - acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump - kernels. - add_efi_memmap [EFI; X86] Include EFI memory map in kernel's map of available physical RAM.

On Thursday, May 14, 2015 10:36:52 PM Rafael J. Wysocki wrote:

On Thursday, May 14, 2015 03:31:26 PM Dominik Brodowski wrote:

...

By using a module parameter named acpi.supported_rev=<value>, the BIOS may be told a different supported ACPI revision compared to the default (which currently is 5, but will be modified to 2 when the revert of b1ef29725865 is reverted).

Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net

Documentation/kernel-parameters.txt | 14 ++++++++++++++ drivers/acpi/osl.c | 16 ++++++++++++++++ 2 files changed, 30 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 61ab162..75f1f8e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -335,6 +335,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted. to assume that this machine's pmtimer latches its value and always returns good values.

• acpi.rev= [HW,ACPI]

• 	Tell ACPI BIOS the supported ACPI REV
  

• 	Format: <int> in range 0..5
  

• 	Up to and including Linux v4.1, the BIOS was told which
  

• 	ACPI revision the ACPICA subsystem in Linux actually
  

• 	supports (which was 5 at the time); from v4.2 on, this
  

• 	value will be set statically to 2 to match the behavior
  

• 	of other ACPI implementations. As some BIOS may operate
  

• 	differently depending on which value _REV is set to, this
  

• 	parameter offers the capability to specify what to export
  

• 	to the BIOS. Note that such changes in the behavior of
  

• 	the BIOS may only be visible after cold booting the
  

• 	system with this parameter _twice_.
  

• acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low }

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index db14a66..caa52f7 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -538,6 +538,11 @@ acpi_os_get_physical_address(void *virt, acpi_physical_address * phys)

static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN];

+/* acpi_supported_rev is 0 in case of no override; overrides are limited to

• • values between 1 to 5. To simplify casting, use an unsigned long */

+static unsigned long acpi_supported_rev; +module_param_named(rev, acpi_supported_rev, ulong, 0);

acpi_status acpi_os_predefined_override(const struct acpi_predefined_names *init_val, char **new_val) @@ -552,6 +557,17 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val, *new_val = acpi_os_name; }

• if (!memcmp(init_val->name, "_REV", 4) && (acpi_supported_rev > 0)) {

• if (acpi_supported_rev <= 5) {
  

So the only value that would really make sense here is 5.

1 should never ever be used with Linux, 2 is the default, 3 is equivalent to 5 for all practical purposes and 4 has never been used in practice, so it is meaningless.

I'd be better to rename the command line switch to acpi.rev_override and simply do "acpi_supported_rev = 5" for it as well as in acpi_set_supported_rev() in [3/4].

...

• 	printk(KERN_INFO PREFIX
  

• 		"Overriding _REV definition to %lu\n",
  

• 		acpi_supported_rev);
  

• 	*new_val = (char *) acpi_supported_rev;
  

• } else
  

• 	printk(KERN_INFO PREFIX
  

• 		"_REV override must be between 1 to 5");
  

• }
• return AE_OK;

}

Overall, what about the appended patch instead of your [2-3/4] (modulo the new command line parameter description which is missing here ATM)?

--- drivers/acpi/Kconfig | 22 ++++++++++++++++++++++ drivers/acpi/blacklist.c | 26 ++++++++++++++++++++++++++ drivers/acpi/internal.h | 4 ++++ drivers/acpi/osl.c | 18 ++++++++++++++++++ 4 files changed, 70 insertions(+)

Index: linux-pm/drivers/acpi/blacklist.c =================================================================== --- linux-pm.orig/drivers/acpi/blacklist.c +++ linux-pm/drivers/acpi/blacklist.c @@ -162,6 +162,15 @@ static int __init dmi_disable_osi_win8(c acpi_osi_setup("!Windows 2012"); return 0; } +#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE +static int __init dmi_enable_rev_override(const struct dmi_system_id *d) +{ + printk(KERN_NOTICE PREFIX "DMI detected: %s (force ACPI _REV to 5)\n", + d->ident); + acpi_rev_override_setup(NULL); + return 0; +} +#endif

static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { { @@ -325,6 +334,23 @@ static struct dmi_system_id acpi_osi_dmi DMI_MATCH(DMI_PRODUCT_NAME, "1015PX"), }, }, + +#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE + /* + * DELL XPS 13 (2015) switches sound between HDA and I2S + * depending on the ACPI _REV callback. If userspace supports + * I2S sufficiently (or if you do not care about sound), you + * can safely disable this quirk. + */ + { + .callback = dmi_enable_rev_override, + .ident = "DELL XPS 13 (2015)", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."), + DMI_MATCH(DMI_PRODUCT_NAME, "XPS 13 9343"), + }, + }, +#endif {} };

Index: linux-pm/drivers/acpi/internal.h =================================================================== --- linux-pm.orig/drivers/acpi/internal.h +++ linux-pm/drivers/acpi/internal.h @@ -23,6 +23,10 @@

#define PREFIX "ACPI: "

+#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE +int __init acpi_rev_override_setup(char *str); +#endif + acpi_status acpi_os_initialize1(void); int init_acpi_device_notify(void); int acpi_scan_init(void); Index: linux-pm/drivers/acpi/osl.c =================================================================== --- linux-pm.orig/drivers/acpi/osl.c +++ linux-pm/drivers/acpi/osl.c @@ -534,6 +534,19 @@ acpi_os_get_physical_address(void *virt, } #endif

+#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE +static bool acpi_rev_override; + +int __init acpi_rev_override_setup(char *str) +{ + acpi_rev_override = true; + return 1; +} +__setup("acpi_rev_override", acpi_rev_override_setup); +#else +#define acpi_rev_override false +#endif + #define ACPI_MAX_OVERRIDE_LEN 100

static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN]; @@ -552,6 +565,11 @@ acpi_os_predefined_override(const struct *new_val = acpi_os_name; }

+ if (!memcmp(init_val->name, "_REV", 4) && acpi_rev_override) { + printk(KERN_INFO PREFIX "Overriding _REV return value to 5\n"); + *new_val = (char *)5; + } + return AE_OK; }

Index: linux-pm/drivers/acpi/Kconfig =================================================================== --- linux-pm.orig/drivers/acpi/Kconfig +++ linux-pm/drivers/acpi/Kconfig @@ -428,6 +428,28 @@ config XPOWER_PMIC_OPREGION help This config adds ACPI operation region support for XPower AXP288 PMIC.

++config ACPI_REV_OVERRIDE_POSSIBLE + bool "Allow supported ACPI revision to be overriden" + depends on X86 + default y + help + The platform firmware on some systems expects Linux to return "5" as + the supported ACPI revision which makes it expose system configuration + information in a special way. + + For example, based on what ACPI exports as the supported revision, + Dell XPS 13 (2015) configures its audio device to either work in HDA + mode or in I2S mode, where the former is supposed to be used on Linux + until the latter is fully supported (in the kernel as well as in user + space). + + This option enables a DMI-based quirk for the above Dell machine (so + that HDA audio is exposed by the platform firmware to the kernel) and + makes it possible to force the kernel to return "5" as the supported + ACPI revision via the "acpi_rev_override" command line switch (when + using that switch it may be necessary to carry out a cold reboot + _twice_ in a row to make it take effect on the firmware). + endif

endif # ACPI

On Thu, May 14, 2015 at 11:55:33 PM Rafael J. Wysocki wrote:

On Thursday, May 14, 2015 10:36:52 PM Rafael J. Wysocki wrote:

...

So the only value that would really make sense here is 5.

Overall, what about the appended patch instead of your [2-3/4] (modulo the new command line parameter description which is missing here ATM)?

Well, this approach works as well -- limiting it to an override for just 5 seems reasonable; expanding blacklist.c to also cover this case (even though it's not a blacklisting per se) isn't worth any discussion.

Nonetheless, a few specifics:

+config ACPI_REV_OVERRIDE_POSSIBLE

Why should that be a config option at all? The code savings should be really, really tiny; and especially in the beginning we might see a few machines where testing the override might seem to be a good idea. So I'd favour having the command line optional, and then only specific quirks behind a config option: For the Dell XPS 13 it makes sense to disable the quirk if userspace can manage i2s sound; for other systems, there may not be such hope. And as this is a machine-specific decision, I fear that we have to do CONFIG options for each and every such DMI entry.

+#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE +static bool acpi_rev_override;

+int __init acpi_rev_override_setup(char *str) +{

• acpi_rev_override = true;
• return 1;

+} +__setup("acpi_rev_override", acpi_rev_override_setup); +#else +#define acpi_rev_override false +#endif

Why __setup, and not module_param? Should mean a smaller diffstat...

So, here's what I'd do based on your modification:

Documentation/kernel-parameters.txt | 16 ++++++++++++++++ drivers/acpi/Kconfig | 20 ++++++++++++++++++++ drivers/acpi/blacklist.c | 26 ++++++++++++++++++++++++++ drivers/acpi/internal.h | 1 + drivers/acpi/osl.c | 8 ++++++++ 5 files changed, 71 insertions(+)

[PATCH] acpi: override to set _REV, especially on Dell XPS 13 (2015)

By using a module parameter named acpi.override_rev=1, the BIOS may be told a different supported ACPI revision compared to the default (which currently is 5, but will be modified to 2 when the revert of b1ef29725865 is reverted).

Such an override is needed, for example, on a Dell XPS 13 (2015): Based on what ACPI exports as is supported version (_REV), the firmware configures the audio device to either work in HDA mode or in I2S mode. As the latter only works on sufficiently new userspace, add a quirk and an associated config option to force sound to HDA mode.

Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 61ab162..1edb048 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -335,6 +335,22 @@ bytes respectively. Such letter suffixes can also be entirely omitted. to assume that this machine's pmtimer latches its value and always returns good values.

+ acpi.rev_override= [HW,ACPI] + Export 5 as the supported ACPI REV + Format: { "0" | "1" } (0 = DMI-based quirks, + 1 = force-enabled) + Up to and including Linux v4.1, the BIOS was told which + ACPI revision the ACPICA subsystem in Linux actually + supports (which was 5 at the time); from v4.2 on, this + value will be set statically to 2 to match the behavior + of other ACPI implementations. As some BIOS may operate + differently depending on which value _REV is set to, this + parameter offers the capability to specify that the + previously used value 5 is to be exported to the firmware. + Note that such changes in the behavior of the BIOS may + only be visible after cold booting the system with this + parameter _twice_. + acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low }

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig index ab2cbb5..a5272c2 100644 --- a/drivers/acpi/Kconfig +++ b/drivers/acpi/Kconfig @@ -430,4 +430,24 @@ config XPOWER_PMIC_OPREGION

endif

+config ACPI_REV_OVERRIDE_DELL_XPS_13_2015 + bool "Dell XPS 13 (2015) quirk to force HDA sound" + depends on X86 && SND_HDA + default y + help + Based on what ACPI exports as the supported revision to the firmware, + Dell XPS 13 (2015) configures its audio device to either work in HDA + mode or in I2S mode, where the former is supposed to be used on Linux + until the latter is fully supported (in the kernel as well as in user + space). + + This option enables a DMI-based quirk for the above Dell machine (so + that HDA audio is exposed by the platform firmware to the kernel) and + makes it possible to force the kernel to return "5" as the supported + ACPI revision via the "acpi_rev_override" command line switch (when + using that switch it may be necessary to carry out a cold reboot + _twice_ in a row to make it take effect on the firmware). + + If in doubt, say Y. + endif # ACPI diff --git a/drivers/acpi/blacklist.c b/drivers/acpi/blacklist.c index 1d17919..ed55ad7 100644 --- a/drivers/acpi/blacklist.c +++ b/drivers/acpi/blacklist.c @@ -162,6 +162,15 @@ static int __init dmi_disable_osi_win8(const struct dmi_system_id *d) acpi_osi_setup("!Windows 2012"); return 0; } +#ifdef CONFIG_ACPI_REV_OVERRIDE_DELL_XPS_13_2015 +static int __init dmi_enable_rev_override(const struct dmi_system_id *d) +{ + printk(KERN_NOTICE PREFIX "DMI detected: %s (force ACPI _REV to 5)\n", + d->ident); + acpi_rev_override = true; + return 0; +} +#endif

static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { { @@ -325,6 +334,23 @@ static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { DMI_MATCH(DMI_PRODUCT_NAME, "1015PX"), }, }, + +#ifdef CONFIG_ACPI_REV_OVERRIDE_DELL_XPS_13_2015 + /* + * DELL XPS 13 (2015) switches sound between HDA and I2S + * depending on the ACPI _REV callback. If userspace supports + * I2S sufficiently (or if you do not care about sound), you + * can safely disable this quirk. + */ + { + .callback = dmi_enable_rev_override, + .ident = "DELL XPS 13 (2015)", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."), + DMI_MATCH(DMI_PRODUCT_NAME, "XPS 13 9343"), + }, + }, +#endif {} };

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h index ba4a61e..fc8db23 100644 --- a/drivers/acpi/internal.h +++ b/drivers/acpi/internal.h @@ -23,6 +23,7 @@

#define PREFIX "ACPI: "

+extern bool acpi_rev_override; acpi_status acpi_os_initialize1(void); int init_acpi_device_notify(void); int acpi_scan_init(void); diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index 7ccba39..4d020d0 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -534,6 +534,9 @@ acpi_os_get_physical_address(void *virt, acpi_physical_address * phys) } #endif

+bool acpi_rev_override; +module_param_named(rev_override, acpi_rev_override, bool, 0); + #define ACPI_MAX_OVERRIDE_LEN 100

static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN]; @@ -552,6 +555,11 @@ acpi_os_predefined_override(const struct acpi_predefined_names *init_val, *new_val = acpi_os_name; }

+ if (!memcmp(init_val->name, "_REV", 4) && acpi_rev_override) { + printk(KERN_INFO PREFIX "Overriding _REV return value to 5\n"); + *new_val = (char *)5; + } + return AE_OK; }

On Saturday, May 23, 2015 12:15:54 AM Rafael J. Wysocki wrote:

On Friday, May 22, 2015 04:19:05 PM Mario_Limonciello@Dell.com wrote:

...

...

OK, so do we have any proof that anything in addition to the sound thing is broken by returning 2 from _REV?

If not, then we're probably spending too much time discussing this.

From a Dell perspective I'm not aware of anything else breaking, but I'll be sure to raise its attention and any associated details if I become privy to them. I'm working with architecture to ensure that future products are not relying on _REV values as well. I know Matthew had mentioned that another OEM's product was using this as well, but I don't know what for.

OK, here's a deal.

I'll wait for the next few days for someone to tell me if there's any known system in addition to the XPS 13 (2015) which breaks as a result of the change to return 2 from _REV. If none are reported before the next Friday, I'll just apply the patch I posted some time ago. If any reports come in later, we'll still be able to rearrange things during the 4.2 cycle or even later.

If *something* is reported next week, I'll reconsider the approach depending on what that thing is.

OK, so nobody has reported anything and below is the patch I'm planning to apply (before restoring _REV=2).

Please let me know if there are objections.

Thanks, Rafael

--- From: Rafael J. Wysocki rafael.j.wysocki@intel.com Subject: ACPI / init: Make it possible to override _REV

The platform firmware on some systems expects Linux to return "5" as the supported ACPI revision which makes it expose system configuration information in a special way.

For example, based on what ACPI exports as the supported revision, Dell XPS 13 (2015) configures its audio device to either work in HDA mode or in I2S mode, where the former is supposed to be used on Linux until the latter is fully supported (in the kernel as well as in user space).

Since ACPI 6 mandates that _REV should return "2" if ACPI 2 or later is supported by the OS, a subsequent change will make that happen, so make it possible to override that on systems where "5" is expected to be returned for Linux to work correctly one them (such as the Dell machine mentioned above).

Original-by: Dominik Brodowski linux@dominikbrodowski.net Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com --- Documentation/kernel-parameters.txt | 6 ++++++ drivers/acpi/Kconfig | 20 ++++++++++++++++++++ drivers/acpi/blacklist.c | 26 ++++++++++++++++++++++++++ drivers/acpi/internal.h | 1 + drivers/acpi/osl.c | 18 ++++++++++++++++++ 5 files changed, 71 insertions(+)

Index: linux-pm/drivers/acpi/blacklist.c =================================================================== --- linux-pm.orig/drivers/acpi/blacklist.c +++ linux-pm/drivers/acpi/blacklist.c @@ -162,6 +162,15 @@ static int __init dmi_disable_osi_win8(c acpi_osi_setup("!Windows 2012"); return 0; } +#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE +static int __init dmi_enable_rev_override(const struct dmi_system_id *d) +{ + printk(KERN_NOTICE PREFIX "DMI detected: %s (force ACPI _REV to 5)\n", + d->ident); + acpi_rev_override_setup(NULL); + return 0; +} +#endif

static struct dmi_system_id acpi_osi_dmi_table[] __initdata = { { @@ -325,6 +334,23 @@ static struct dmi_system_id acpi_osi_dmi DMI_MATCH(DMI_PRODUCT_NAME, "1015PX"), }, }, + +#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE + /* + * DELL XPS 13 (2015) switches sound between HDA and I2S + * depending on the ACPI _REV callback. If userspace supports + * I2S sufficiently (or if you do not care about sound), you + * can safely disable this quirk. + */ + { + .callback = dmi_enable_rev_override, + .ident = "DELL XPS 13 (2015)", + .matches = { + DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."), + DMI_MATCH(DMI_PRODUCT_NAME, "XPS 13 9343"), + }, + }, +#endif {} };

Index: linux-pm/drivers/acpi/internal.h =================================================================== --- linux-pm.orig/drivers/acpi/internal.h +++ linux-pm/drivers/acpi/internal.h @@ -58,6 +58,7 @@ void acpi_cmos_rtc_init(void); #else static inline void acpi_cmos_rtc_init(void) {} #endif +int acpi_rev_override_setup(char *str);

extern bool acpi_force_hot_remove;

Index: linux-pm/drivers/acpi/osl.c =================================================================== --- linux-pm.orig/drivers/acpi/osl.c +++ linux-pm/drivers/acpi/osl.c @@ -530,6 +530,19 @@ acpi_os_get_physical_address(void *virt, } #endif

+#ifdef CONFIG_ACPI_REV_OVERRIDE_POSSIBLE +static bool acpi_rev_override; + +int __init acpi_rev_override_setup(char *str) +{ + acpi_rev_override = true; + return 1; +} +__setup("acpi_rev_override", acpi_rev_override_setup); +#else +#define acpi_rev_override false +#endif + #define ACPI_MAX_OVERRIDE_LEN 100

static char acpi_os_name[ACPI_MAX_OVERRIDE_LEN]; @@ -548,6 +561,11 @@ acpi_os_predefined_override(const struct *new_val = acpi_os_name; }

+ if (!memcmp(init_val->name, "_REV", 4) && acpi_rev_override) { + printk(KERN_INFO PREFIX "Overriding _REV return value to 5\n"); + *new_val = (char *)5; + } + return AE_OK; }

Index: linux-pm/drivers/acpi/Kconfig =================================================================== --- linux-pm.orig/drivers/acpi/Kconfig +++ linux-pm/drivers/acpi/Kconfig @@ -431,6 +431,26 @@ config XPOWER_PMIC_OPREGION help This config adds ACPI operation region support for XPower AXP288 PMIC.

++config ACPI_REV_OVERRIDE_POSSIBLE + bool "Allow supported ACPI revision to be overriden" + depends on X86 + default y + help + The platform firmware on some systems expects Linux to return "5" as + the supported ACPI revision which makes it expose system configuration + information in a special way. + + For example, based on what ACPI exports as the supported revision, + Dell XPS 13 (2015) configures its audio device to either work in HDA + mode or in I2S mode, where the former is supposed to be used on Linux + until the latter is fully supported (in the kernel as well as in user + space). + + This option enables a DMI-based quirk for the above Dell machine (so + that HDA audio is exposed by the platform firmware to the kernel) and + makes it possible to force the kernel to return "5" as the supported + ACPI revision via the "acpi_rev_override" command line switch. + endif

endif # ACPI Index: linux-pm/Documentation/kernel-parameters.txt =================================================================== --- linux-pm.orig/Documentation/kernel-parameters.txt +++ linux-pm/Documentation/kernel-parameters.txt @@ -285,6 +285,12 @@ bytes respectively. Such letter suffixes dynamic table installation which will install SSDT tables to /sys/firmware/acpi/tables/dynamic.

+ acpi_rev_override [ACPI] Override the _REV object to return 5 (instead + of 2 which is mandated by ACPI 6) as the supported ACPI + specification revision (when using this switch, it may + be necessary to carry out a cold reboot _twice_ in a + row to make it take effect on the platform firmware). + acpi_rsdp= [ACPI,EFI,KEXEC] Pass the RSDP address to the kernel, mostly used on machines running EFI runtime service to boot the