linux-kernel - Re: [PATCH] soundwire: qcom: update status from device id 1

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Date:   Fri, 16 Sep 2022 10:12:12 +0100
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, sanyog.r.kale@...el.com,
        linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, quic_srivasam@...cinc.com
Subject: Re: [PATCH] soundwire: qcom: update status from device id 1



On 15/09/2022 14:10, Pierre-Louis Bossart wrote:
> 
> 
> On 9/15/22 14:42, Srinivas Kandagatla wrote:
>> By default autoenumeration is enabled on QCom SoundWire controller
>> which means the core should not be dealing with device 0 w.r.t enumeration.
>> Currently device 0 status is also shared with SoundWire core which confuses
>> the core sometimes and we endup adding 0:0:0:0 slave device.
> 
> The change looks fine, but the description of the issue is surprising.

Thanks Pierre,

> 
> Whether autoenumeration is enabled or not is irrelevant, by spec the
> device0 cannot be in ALERT status and throw in-band interrupts to the
> host with this mechanism.

This issue is more of around enumeration stage in specific during device 
status change interrupt from controller. Sharing the device 0 status 
with core makes it think that there is a device with 0:0:0:0 address and 
it tries to park device to group 13.


--srini

> 
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> ---
>>   drivers/soundwire/qcom.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
>> index e21a3306bf01..871e4d8b32c7 100644
>> --- a/drivers/soundwire/qcom.c
>> +++ b/drivers/soundwire/qcom.c
>> @@ -428,7 +428,7 @@ static int qcom_swrm_get_alert_slave_dev_num(struct qcom_swrm_ctrl *ctrl)
>>   
>>   	ctrl->reg_read(ctrl, SWRM_MCP_SLV_STATUS, &val);
>>   
>> -	for (dev_num = 0; dev_num <= SDW_MAX_DEVICES; dev_num++) {
>> +	for (dev_num = 1; dev_num <= SDW_MAX_DEVICES; dev_num++) {
>>   		status = (val >> (dev_num * SWRM_MCP_SLV_STATUS_SZ));
>>   
>>   		if ((status & SWRM_MCP_SLV_STATUS_MASK) == SDW_SLAVE_ALERT) {
>> @@ -448,7 +448,7 @@ static void qcom_swrm_get_device_status(struct qcom_swrm_ctrl *ctrl)
>>   	ctrl->reg_read(ctrl, SWRM_MCP_SLV_STATUS, &val);
>>   	ctrl->slave_status = val;
>>   
>> -	for (i = 0; i <= SDW_MAX_DEVICES; i++) {
>> +	for (i = 1; i <= SDW_MAX_DEVICES; i++) {
>>   		u32 s;
>>   
>>   		s = (val >> (i * 2));