linux-kernel - Re: [PATCH] soundwire: qcom: Fix enumeration of second device on the bus

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Date:   Wed, 5 Apr 2023 10:01:56 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-arm-msm@...r.kernel.org, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Patrick Lai <quic_plai@...cinc.com>
Subject: Re: [PATCH] soundwire: qcom: Fix enumeration of second device on the
 bus



On 4/5/23 09:29, Krzysztof Kozlowski wrote:
> Some Soundwire buses (like &swr0 on Qualcomm HDK8450) have two devices,
> which can be brought from powerdown state one after another.  We need to
> keep enumerating them on each slave attached interrupt, otherwise only
> first will appear.
> 
> Cc: <stable@...r.kernel.org>
> Fixes: a6e6581942ca ("soundwire: qcom: add auto enumeration support")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> ---
> 
> Cc: Patrick Lai <quic_plai@...cinc.com>
> ---
>  drivers/soundwire/qcom.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> index c296e0bf897b..1e5077d91f59 100644
> --- a/drivers/soundwire/qcom.c
> +++ b/drivers/soundwire/qcom.c
> @@ -587,14 +587,9 @@ static irqreturn_t qcom_swrm_irq_handler(int irq, void *dev_id)
>  			case SWRM_INTERRUPT_STATUS_CHANGE_ENUM_SLAVE_STATUS:
>  				dev_dbg_ratelimited(swrm->dev, "SWR new slave attached\n");
>  				swrm->reg_read(swrm, SWRM_MCP_SLV_STATUS, &slave_status);
> -				if (swrm->slave_status == slave_status) {
> -					dev_dbg(swrm->dev, "Slave status not changed %x\n",
> -						slave_status);

it's not clear to me how removing this test helps with the two-device
configuration?

Or is this a case where the status for both devices changes at the same
time but the interrupt status remains set, so the next iteration of the
loop is ignored?

> -				} else {
> -					qcom_swrm_get_device_status(swrm);
> -					qcom_swrm_enumerate(&swrm->bus);
> -					sdw_handle_slave_status(&swrm->bus, swrm->status);
> -				}
> +				qcom_swrm_get_device_status(swrm);
> +				qcom_swrm_enumerate(&swrm->bus);
> +				sdw_handle_slave_status(&swrm->bus, swrm->status);
>  				break;
>  			case SWRM_INTERRUPT_STATUS_MASTER_CLASH_DET:
>  				dev_err_ratelimited(swrm->dev,