linux-kernel - Re: [PATCH V5 2/2] firmware: qcom: scm: Add wait-queue handling logic

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Date:   Thu, 24 Nov 2022 12:21:49 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Sibi Sankar <quic_sibis@...cinc.com>, andersson@...nel.org
Cc:     agross@...nel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        konrad.dybcio@...ainline.org, robimarko@...il.com,
        quic_gurus@...cinc.com, quic_rjendra@...cinc.com
Subject: Re: [PATCH V5 2/2] firmware: qcom: scm: Add wait-queue handling logic

On 23/11/2022 21:46, Sibi Sankar wrote:
> From: Guru Das Srinagesh <quic_gurus@...cinc.com>
> 
> When the firmware (FW) supports multiple requests per VM, multiple requests
> from the same/different VM can reach the firmware at the same time. Since
> the firmware currently being used has limited resources, it guards them
> with a resource lock and puts requests on a wait-queue internally and
> signals to HLOS that it is doing so. It does this by returning a new return
> value in addition to success or error: SCM_WAITQ_SLEEP. A sleeping SCM call
> can be woken up by an interrupt that the FW raises.

Just two nitpicks while browsing the code...

>  static int qcom_scm_probe(struct platform_device *pdev)
>  {
>  	struct qcom_scm *scm;
>  	unsigned long clks;
> -	int ret;
> +	int irq, ret;
>  
>  	scm = devm_kzalloc(&pdev->dev, sizeof(*scm), GFP_KERNEL);
>  	if (!scm)
> @@ -1399,9 +1486,29 @@ static int qcom_scm_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> +	platform_set_drvdata(pdev, scm);
> +
>  	__scm = scm;
>  	__scm->dev = &pdev->dev;
>  
> +	spin_lock_init(&__scm->waitq.idr_lock);
> +	idr_init(&__scm->waitq.idr);
> +	init_completion(&__scm->waitq.waitq_comp);
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		if (irq != -ENXIO)
> +			return irq;
> +	} else {
> +		ret = devm_request_threaded_irq(__scm->dev, irq, NULL, qcom_scm_irq_handler,
> +						IRQF_ONESHOT, "qcom-scm", __scm);
> +		if (ret < 0) {
> +			dev_err(scm->dev, "Failed to request qcom-scm irq: %d\n", ret);
> +			idr_destroy(&__scm->waitq.idr);
> +			return ret;

return dev_err_probe().

> +		}
> +	}
> +
>  	__get_convention();
>  
>  	/*
> @@ -1417,6 +1524,12 @@ static int qcom_scm_probe(struct platform_device *pdev)
>  
>  static void qcom_scm_shutdown(struct platform_device *pdev)
>  {
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&__scm->waitq.idr_lock, flags);
> +	idr_destroy(&__scm->waitq.idr);
> +	spin_unlock_irqrestore(&__scm->waitq.idr_lock, flags);
> +
>  	/* Clean shutdown, disable download mode to allow normal restart */
>  	if (download_mode)
>  		qcom_scm_set_download_mode(false);
> diff --git a/drivers/firmware/qcom_scm.h b/drivers/firmware/qcom_scm.h
> index db3d08a01209..323cb49d4976 100644
> --- a/drivers/firmware/qcom_scm.h
> +++ b/drivers/firmware/qcom_scm.h
> @@ -60,6 +60,10 @@ struct qcom_scm_res {
>  	u64 result[MAX_QCOM_SCM_RETS];
>  };
>  
> +struct qcom_scm;
> +extern struct completion *qcom_scm_lookup_wq(struct qcom_scm *scm, u32 wq_ctx);
> +extern int scm_get_wq_ctx(u32 *wq_ctx, u32 *flags, u32 *more_pending);

No need for externs for new entries.

Best regards,
Krzysztof