linux-kernel - Re: [PATCH 2/2] media: imx-mipi-csis: Drop extra clock enable at probe()

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Message-ID: <20231122150410.GF8627@pendragon.ideasonboard.com>
Date:   Wed, 22 Nov 2023 17:04:10 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     Kieran Bingham <kieran.bingham@...asonboard.com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Martin Kepplinger <martink@...teo.de>,
        Purism Kernel Team <kernel@...i.sm>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] media: imx-mipi-csis: Drop extra clock enable at
 probe()

Hi Tomi,

Thank you for the patch.

On Wed, Nov 22, 2023 at 03:13:49PM +0200, Tomi Valkeinen wrote:
> The driver always enables the clocks at probe() and disables them only
> at remove(). It is not clear why the driver does this, as it supports
> runtime PM, and enables and disables the clocks in the runtime resume
> and suspend callbacks. Also, in the case runtime PM is not available,
> the driver calls the resume and suspend callbacks manually from probe()
> and remove().

Probably a historical mistake. It predates my involvement with the
driver :-)

> Drop the unnecessary clock enable, thus enabling the clocks only when
> actually needed.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
>  drivers/media/platform/nxp/imx-mipi-csis.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> index b39d7aeba750..b08f6d2e7516 100644
> --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> @@ -1435,24 +1435,18 @@ static int mipi_csis_probe(struct platform_device *pdev)
>  	/* Reset PHY and enable the clocks. */
>  	mipi_csis_phy_reset(csis);
>  
> -	ret = mipi_csis_clk_enable(csis);
> -	if (ret < 0) {
> -		dev_err(csis->dev, "failed to enable clocks: %d\n", ret);
> -		return ret;
> -	}
> -
>  	/* Now that the hardware is initialized, request the interrupt. */
>  	ret = devm_request_irq(dev, irq, mipi_csis_irq_handler, 0,
>  			       dev_name(dev), csis);
>  	if (ret) {
>  		dev_err(dev, "Interrupt request failed\n");
> -		goto err_disable_clock;
> +		return ret;
>  	}
>  
>  	/* Initialize and register the subdev. */
>  	ret = mipi_csis_subdev_init(csis);
>  	if (ret < 0)
> -		goto err_disable_clock;
> +		return ret;
>  
>  	platform_set_drvdata(pdev, &csis->sd);
>  
> @@ -1486,8 +1480,6 @@ static int mipi_csis_probe(struct platform_device *pdev)
>  	v4l2_async_nf_unregister(&csis->notifier);
>  	v4l2_async_nf_cleanup(&csis->notifier);
>  	v4l2_async_unregister_subdev(&csis->sd);
> -err_disable_clock:
> -	mipi_csis_clk_disable(csis);
>  
>  	return ret;
>  }
> @@ -1506,7 +1498,6 @@ static void mipi_csis_remove(struct platform_device *pdev)
>  		mipi_csis_runtime_suspend(&pdev->dev);
>  
>  	pm_runtime_disable(&pdev->dev);
> -	mipi_csis_clk_disable(csis);
>  	v4l2_subdev_cleanup(&csis->sd);
>  	media_entity_cleanup(&csis->sd.entity);
>  	pm_runtime_set_suspended(&pdev->dev);
> 

-- 
Regards,

Laurent Pinchart