ASoC: SOF: Intel: hda: add a parameter to disable MSI

Enabling MSI on HDA can fail, in which case the legacy PCI IRQ mode
will be used. To make testing this mode easier add an "enable_msi"
module parameter, which is only enabled if debugging is enabled too.
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190722141402.7194-17-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/hda.c

@@ -46,6 +46,12 @@ struct hda_dsp_msg_code {
 	const char *msg;
 };
 
+static bool hda_use_msi = IS_ENABLED(CONFIG_PCI);
+#if IS_ENABLED(CONFIG_SND_SOC_SOF_DEBUG)
+module_param_named(use_msi, hda_use_msi, bool, 0444);
+MODULE_PARM_DESC(use_msi, "SOF HDA use PCI MSI mode");
+#endif
+
 static const struct hda_dsp_msg_code hda_dsp_rom_msg[] = {
 	{HDA_DSP_ROM_FW_MANIFEST_LOADED, "status: manifest loaded"},
 	{HDA_DSP_ROM_FW_FW_LOADED, "status: fw loaded"},
@@ -529,11 +535,18 @@ int hda_dsp_probe(struct snd_sof_dev *sdev)
 	 * register our IRQ
 	 * let's try to enable msi firstly
 	 * if it fails, use legacy interrupt mode
-	 * TODO: support interrupt mode selection with kernel parameter
-	 *       support msi multiple vectors
+	 * TODO: support msi multiple vectors
 	 */
-	ret = pci_alloc_irq_vectors(pci, 1, 1, PCI_IRQ_MSI);
-	if (ret < 0) {
+	if (hda_use_msi && !pci_alloc_irq_vectors(pci, 1, 1, PCI_IRQ_MSI)) {
+		dev_info(sdev->dev, "use msi interrupt mode\n");
+		hdev->irq = pci_irq_vector(pci, 0);
+		/* ipc irq number is the same of hda irq */
+		sdev->ipc_irq = hdev->irq;
+		/* initialised to "false" by kzalloc() */
+		sdev->msi_enabled = true;
+	}
+
+	if (!sdev->msi_enabled) {
 		dev_info(sdev->dev, "use legacy interrupt mode\n");
 		/*
 		 * in IO-APIC mode, hda->irq and ipc_irq are using the same
@@ -541,13 +554,6 @@ int hda_dsp_probe(struct snd_sof_dev *sdev)
 		 */
 		hdev->irq = pci->irq;
 		sdev->ipc_irq = pci->irq;
-		sdev->msi_enabled = 0;
-	} else {
-		dev_info(sdev->dev, "use msi interrupt mode\n");
-		hdev->irq = pci_irq_vector(pci, 0);
-		/* ipc irq number is the same of hda irq */
-		sdev->ipc_irq = hdev->irq;
-		sdev->msi_enabled = 1;
 	}
 
 	dev_dbg(sdev->dev, "using HDA IRQ %d\n", hdev->irq);

sound/soc/sof/sof-priv.h

@@ -435,7 +435,7 @@ struct snd_sof_dev {
 	u32 dtrace_error;
 	u32 dtrace_draining;
 
-	u32 msi_enabled;
+	bool msi_enabled;
 
 	void *private;			/* core does not touch this */
 };