[alsa-devel] [PATCH] ALSA: cmipci: Allow disabling MPU port via module option
Patrick May reported that his sound card with CMI8378 chip causes a crash / reboot when accessing the MIDI port that isn't actually present on the board. Moreover, despite of the documentation, passing mpu_port=0 doesn't disable the MIDI port on this board.
It implies that the chip is a newer revision and the MPU401 port is integrated and mapped on the PCI register. For this chip model, the driver enables the MPU port unconditionally, so far.
Although fixing the unexpected reboot would be the best solution, it's not so trivial to identify the cause. So, as a plan B, this patch extends the existing mpu_port option usage to allow disabling the port by specifying the value 0, just like we applied for fm_port option in commit 2f24d159d5ac ("[ALSA] cmipci - Allow to disable integrated FM port"). As default, the MPU port is still enabled, but user can pass mpu_port=0 to disable it.
Reported-and-tested-by: Patrick May dusthillresident@gmail.com Signed-off-by: Takashi Iwai tiwai@suse.de --- Documentation/sound/alsa-configuration.rst | 3 ++- sound/pci/cmipci.c | 5 +++-- 2 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst index 02aacd69ab96..392875a1b94e 100644 --- a/Documentation/sound/alsa-configuration.rst +++ b/Documentation/sound/alsa-configuration.rst @@ -495,7 +495,8 @@ Module for C-Media CMI8338/8738/8768/8770 PCI sound cards. mpu_port port address of MIDI interface (8338 only): 0x300,0x310,0x320,0x330 = legacy port, - 0 = disable (default) + 1 = integrated PCI port (default on 8738), + 0 = disable fm_port port address of OPL-3 FM synthesizer (8x38 only): 0x388 = legacy port, diff --git a/sound/pci/cmipci.c b/sound/pci/cmipci.c index 4bfab21c53f4..266c4cf28b78 100644 --- a/sound/pci/cmipci.c +++ b/sound/pci/cmipci.c @@ -42,7 +42,7 @@ MODULE_SUPPORTED_DEVICE("{{C-Media,CMI8738}," static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX; /* Index 0-MAX */ static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR; /* ID for this card */ static bool enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP; /* Enable switches */ -static long mpu_port[SNDRV_CARDS]; +static long mpu_port[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS-1)] = 1}; static long fm_port[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS-1)]=1}; static bool soft_ac3[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS-1)]=1}; #ifdef SUPPORT_JOYSTICK @@ -3132,7 +3132,8 @@ static int snd_cmipci_create(struct snd_card *card, struct pci_dev *pci, if (cm->chip_version >= 39) { val = snd_cmipci_read_b(cm, CM_REG_MPU_PCI + 1); if (val != 0x00 && val != 0xff) { - iomidi = cm->iobase + CM_REG_MPU_PCI; + if (mpu_port[dev]) + iomidi = cm->iobase + CM_REG_MPU_PCI; integrated_midi = 1; } }
Takashi Iwai wrote:
Patrick May reported that his sound card with CMI8378 chip causes a crash / reboot when accessing the MIDI port that isn't actually present on the board. [...] Although fixing the unexpected reboot would be the best solution, it's not so trivial to identify the cause.
There was a similar problem in the CMI8788 driver: https://git.kernel.org/linus/f1bc07af9a9e https://bugtrack.alsa-project.org/alsa-bug/view.php?id=4496 (does this still exist?)
When reading a register repeatedly, the chip sometimes does not complete the PCI transaction. Apparently, mainboard PCI chipsets ignore this error, but PCIe/PCI bridges generate a machine check exception in this case.
When writing MIDI data to a MPU-401-like device, the driver regularly polls the status register. I expect that this will blow up with any C-Media chip on a card with a PCIe/PCI bridge, regardless of whether a MIDI port exists.
(I wonder if this can be triggered with snd_pcm_avail() in a loop. Maybe it happens only for byte accesses, or nobody has yet found out.)
As default, the MPU port is still enabled
It might be a good idea to disable it by default if the parent bridge is an ASM1083.
Regards, Clemens
participants (2)
-
Clemens Ladisch -
Takashi Iwai