linux-kernel - Re: [PATCH v5 3/4] media: imx8mq-mipi-csi2: Explicitly release reset

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Message-ID: <20250901153632.GA13448@pendragon.ideasonboard.com>
Date: Mon, 1 Sep 2025 17:36:32 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Guoniu Zhou <guoniu.zhou@....com>
Cc: Rui Miguel Silva <rmfrfs@...il.com>,
	Martin Kepplinger <martink@...teo.de>,
	Purism Kernel Team <kernel@...i.sm>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Philipp Zabel <p.zabel@...gutronix.de>, Frank Li <Frank.Li@....com>,
	linux-media@...r.kernel.org, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/4] media: imx8mq-mipi-csi2: Explicitly release reset

Hi Guoniu,

Thank you for the patch.

On Mon, Sep 01, 2025 at 02:25:31PM +0800, Guoniu Zhou wrote:
> Call reset_control_deassert() to explicitly release reset to make sure
> reset bits are cleared since platform like i.MX8ULP can't clear reset
> bits automatically.
> 
> Reviewed-by: Frank Li <Frank.Li@....com>
> Signed-off-by: Guoniu Zhou <guoniu.zhou@....com>
> ---
>  drivers/media/platform/nxp/imx8mq-mipi-csi2.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/platform/nxp/imx8mq-mipi-csi2.c b/drivers/media/platform/nxp/imx8mq-mipi-csi2.c
> index 2bf11984690af2e687a3217e465697333d9d995d..6b83aa85af42e1dac25cf29056863680c1f89402 100644
> --- a/drivers/media/platform/nxp/imx8mq-mipi-csi2.c
> +++ b/drivers/media/platform/nxp/imx8mq-mipi-csi2.c
> @@ -337,18 +337,14 @@ static int imx8mq_mipi_csi_sw_reset(struct csi_state *state)
>  {
>  	int ret;
>  
> -	/*
> -	 * these are most likely self-clearing reset bits. to make it
> -	 * more clear, the reset-imx7 driver should implement the
> -	 * .reset() operation.

What happened to this plan, would it be feasible to implement the
.reset() operation in the relevant drivers to be able to use
reset_control_reset() here ?

> -	 */
>  	ret = reset_control_assert(state->rst);
>  	if (ret < 0) {
>  		dev_err(state->dev, "Failed to assert resets: %d\n", ret);
>  		return ret;
>  	}
>  
> -	return 0;
> +	/* Explicitly release reset to make sure reset bits are cleared. */
> +	return reset_control_deassert(state->rst);
>  }
>  
>  static void imx8mq_mipi_csi_set_params(struct csi_state *state)

-- 
Regards,

Laurent Pinchart