linux-kernel - Re: [PATCH 3/5] soundwire: qcom: wait for fifo to be empty before suspend

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Message-ID: <a1d79008-3ec4-d7b5-12b5-ea5c6c5a8370@linaro.org>
Date:   Thu, 9 Feb 2023 15:52:29 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        vkoul@...nel.org
Cc:     yung-chuan.liao@...ux.intel.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, steev@...i.org,
        johan+linaro@...nel.org, quic_bjorande@...cinc.com
Subject: Re: [PATCH 3/5] soundwire: qcom: wait for fifo to be empty before
 suspend



On 09/02/2023 15:23, Pierre-Louis Bossart wrote:
> 
> 
> On 2/9/23 07:13, Srinivas Kandagatla wrote:
>> Wait for Fifo to be empty before going to suspend or before bank
>> switch happens. Just to make sure that all the reads/writes are done.
> 
> For the suspend case that seems like a valid approach, but for bank
> switch don't we already have a bus->msg_lock mutex that will prevent the
> bank switch command from being sent before the other commands are handled?

All read/writes are fifo based, so writes could be still pending.

--srini
> 
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>   drivers/soundwire/qcom.c | 29 +++++++++++++++++++++++++++++
>>   1 file changed, 29 insertions(+)
>>
>> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
>> index b2363839624c..465b2a2ef0d5 100644
>> --- a/drivers/soundwire/qcom.c
>> +++ b/drivers/soundwire/qcom.c
>> @@ -325,6 +325,32 @@ static int swrm_wait_for_wr_fifo_avail(struct qcom_swrm_ctrl *swrm)
>>   	return 0;
>>   }
>>   
>> +static bool swrm_wait_for_wr_fifo_done(struct qcom_swrm_ctrl *swrm)
>> +{
>> +	u32 fifo_outstanding_cmds, value;
>> +	int fifo_retry_count = SWR_OVERFLOW_RETRY_COUNT;
>> +
>> +	/* Check for fifo overflow during write */
>> +	swrm->reg_read(swrm, SWRM_CMD_FIFO_STATUS, &value);
>> +	fifo_outstanding_cmds = FIELD_GET(SWRM_WR_CMD_FIFO_CNT_MASK, value);
>> +
>> +	if (fifo_outstanding_cmds) {
>> +		while (fifo_retry_count) {
>> +			usleep_range(500, 510);
>> +			swrm->reg_read(swrm, SWRM_CMD_FIFO_STATUS, &value);
>> +			fifo_outstanding_cmds = FIELD_GET(SWRM_WR_CMD_FIFO_CNT_MASK, value);
>> +			fifo_retry_count--;
>> +			if (fifo_outstanding_cmds == 0)
>> +				return true;
>> +		}
>> +	} else {
>> +		return true;
>> +	}
>> +
>> +
>> +	return false;
>> +}
>> +
>>   static int qcom_swrm_cmd_fifo_wr_cmd(struct qcom_swrm_ctrl *swrm, u8 cmd_data,
>>   				     u8 dev_addr, u16 reg_addr)
>>   {
>> @@ -356,6 +382,7 @@ static int qcom_swrm_cmd_fifo_wr_cmd(struct qcom_swrm_ctrl *swrm, u8 cmd_data,
>>   		usleep_range(150, 155);
>>   
>>   	if (cmd_id == SWR_BROADCAST_CMD_ID) {
>> +		swrm_wait_for_wr_fifo_done(swrm);
>>   		/*
>>   		 * sleep for 10ms for MSM soundwire variant to allow broadcast
>>   		 * command to complete.
>> @@ -1122,6 +1149,7 @@ static void qcom_swrm_shutdown(struct snd_pcm_substream *substream,
>>   {
>>   	struct qcom_swrm_ctrl *ctrl = dev_get_drvdata(dai->dev);
>>   
>> +	swrm_wait_for_wr_fifo_done(ctrl);
>>   	sdw_release_stream(ctrl->sruntime[dai->id]);
>>   	ctrl->sruntime[dai->id] = NULL;
>>   	pm_runtime_mark_last_busy(ctrl->dev);
>> @@ -1558,6 +1586,7 @@ static int __maybe_unused swrm_runtime_suspend(struct device *dev)
>>   	struct qcom_swrm_ctrl *ctrl = dev_get_drvdata(dev);
>>   	int ret;
>>   
>> +	swrm_wait_for_wr_fifo_done(ctrl);
>>   	if (!ctrl->clock_stop_not_supported) {
>>   		/* Mask bus clash interrupt */
>>   		ctrl->intr_mask &= ~SWRM_INTERRUPT_STATUS_MASTER_CLASH_DET;