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

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Date:   Thu, 15 Sep 2022 15:10:18 +0200
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        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 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.

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.

> 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));