ASoC: SOF: mediatek: mt8195 suspend check dsp idle

During suspend flow, sof_suspend will be called and the pm_ops->ctx_save
callback notifies DSP of the upcoming power down.

Upon receipt of the ctx_save IPC, the DSP will start the D3 transition.
Before the DSP enter idle, an interrupt is generated to notify the host of
the power state change.

Since the host and DSP are two different processors, there could be a
race condition, which can be avoided by polling with 1s timeout and 500us
intervals

Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: YC Hung <yc.hung@mediatek.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220606210212.146626-6-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/mediatek/mt8195/mt8195.c

@@ -443,6 +443,19 @@ static int mt8195_dsp_suspend(struct snd_sof_dev *sdev, u32 target_state)
 {
 	struct platform_device *pdev = container_of(sdev->dev, struct platform_device, dev);
 	int ret;
+	u32 reset_sw, dbg_pc;
+
+	/* wait dsp enter idle, timeout is 1 second */
+	ret = snd_sof_dsp_read_poll_timeout(sdev, DSP_REG_BAR,
+					    DSP_RESET_SW, reset_sw,
+					    ((reset_sw & ADSP_PWAIT) == ADSP_PWAIT),
+					    SUSPEND_DSP_IDLE_POLL_INTERVAL_US,
+					    SUSPEND_DSP_IDLE_TIMEOUT_US);
+	if (ret < 0) {
+		dbg_pc = snd_sof_dsp_read(sdev, DSP_REG_BAR, DSP_PDEBUGPC);
+		dev_warn(sdev->dev, "dsp not idle, powering off anyway : swrest %#x, pc %#x, ret %d\n",
+			 reset_sw, dbg_pc, ret);
+	}
 
 	/* stall and reset dsp */
 	sof_hifixdsp_shutdown(sdev);

sound/soc/sof/mediatek/mt8195/mt8195.h

@@ -34,6 +34,7 @@ struct snd_sof_dev;
 #define ADSP_DRESET_SW			BIT(1)
 #define ADSP_RUNSTALL			BIT(3)
 #define STATVECTOR_SEL			BIT(4)
+#define ADSP_PWAIT			BIT(16)
 #define DSP_PFAULTBUS			0x0028
 #define DSP_PFAULTINFO			0x002c
 #define DSP_GPR00			0x0030
@@ -153,6 +154,10 @@ struct snd_sof_dev;
 #define DRAM_REMAP_SHIFT	12
 #define DRAM_REMAP_MASK		(BIT(DRAM_REMAP_SHIFT) - 1)
 
+/* suspend dsp idle check interval and timeout */
+#define SUSPEND_DSP_IDLE_TIMEOUT_US		1000000	/* timeout to wait dsp idle, 1 sec */
+#define SUSPEND_DSP_IDLE_POLL_INTERVAL_US	500	/* 0.5 msec */
+
 void sof_hifixdsp_boot_sequence(struct snd_sof_dev *sdev, u32 boot_addr);
 void sof_hifixdsp_shutdown(struct snd_sof_dev *sdev);
 #endif