[alsa-devel] [PATCH 1/2] ASoC: SOF: pci: change the default firmware path when the community key is used

[Pierre-Louis Bossart]

Since ApolloLake, Intel platforms require signed firmware. On all
Windows platforms the default is to require the Intel production key
be used. But some platforms allow for a community key to be used,
which allows developers to compile/build their own firmware.

In the linux-firmware tree, the default intel/sof path is used for
firmwares signed for the production key, and files signed with the
community key are located in intel/sof/community.

Since we don't have an API to query which key is used on what
platforms, we have to rely on DMI-based quirks.

Developers can bypass this mechanism by setting a kernel 'fw_path'
module parameter. Additional dynamic debug traces are provided to help
debug cases where the wrong file might be used.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 sound/soc/sof/sof-pci-dev.c | 44 +++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/sound/soc/sof/sof-pci-dev.c b/sound/soc/sof/sof-pci-dev.c
index da7b17e5177b..9993be36d105 100644
--- a/sound/soc/sof/sof-pci-dev.c
+++ b/sound/soc/sof/sof-pci-dev.c
@@ -9,6 +9,7 @@
 //
 
 #include <linux/firmware.h>
+#include <linux/dmi.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/pm_runtime.h>
@@ -36,6 +37,23 @@ MODULE_PARM_DESC(sof_pci_debug, "SOF PCI debug options (0x0 all off)");
 
 #define SOF_PCI_DISABLE_PM_RUNTIME BIT(0)
 
+static const struct dmi_system_id community_key_platforms[] = {
+	{
+		.ident = "Up Squared",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "AAEON"),
+			DMI_MATCH(DMI_BOARD_NAME, "UP-APL01"),
+		}
+	},
+	{
+		.ident = "Google Chromebooks",
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Google"),
+		}
+	},
+	{},
+};
+
 #if IS_ENABLED(CONFIG_SND_SOC_SOF_APOLLOLAKE)
 static const struct sof_dev_desc bxt_desc = {
 	.machines		= snd_soc_acpi_intel_bxt_machines,
@@ -290,12 +308,34 @@ static int sof_pci_probe(struct pci_dev *pci,
 	sof_pdata->dev = dev;
 	sof_pdata->fw_filename = desc->default_fw_filename;
 
+	/*
+	 * for platforms using the SOF community key, change the
+	 * default path automatically to pick the right files from the
+	 * linux-firmware tree. This can be overridden with the
+	 * fw_path kernel parameter, e.g. for developers.
+	 */
+
 	/* alternate fw and tplg filenames ? */
-	if (fw_path)
+	if (fw_path) {
 		sof_pdata->fw_filename_prefix = fw_path;
-	else
+
+		dev_dbg(dev,
+			"Module parameter used, changed fw path to %s\n",
+			sof_pdata->fw_filename_prefix);
+
+	} else if (dmi_check_system(community_key_platforms)) {
+		sof_pdata->fw_filename_prefix =
+			devm_kasprintf(dev, GFP_KERNEL, "%s/%s",
+				       sof_pdata->desc->default_fw_path,
+				       "community");
+
+		dev_dbg(dev,
+			"Platform uses community key, changed fw path to %s\n",
+			sof_pdata->fw_filename_prefix);
+	} else {
 		sof_pdata->fw_filename_prefix =
 			sof_pdata->desc->default_fw_path;
+	}
 
 	if (tplg_path)
 		sof_pdata->tplg_filename_prefix = tplg_path;
-- 
2.20.1