linux-kernel - Re: [PATCH v2 09/22] media: rockchip: rga: align stride to 4 bytes

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Message-ID: <98a11ef7e0004267f58a18ad97ea9cb11a68a626.camel@ndufresne.ca>
Date: Wed, 24 Dec 2025 10:26:41 -0500
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Sven Püschel <s.pueschel@...gutronix.de>, Jacob Chen
	 <jacob-chen@...wrt.com>, Ezequiel Garcia <ezequiel@...guardiasur.com.ar>, 
 Mauro Carvalho Chehab
	 <mchehab@...nel.org>, Heiko Stuebner <heiko@...ech.de>, Rob Herring
	 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
	 <conor+dt@...nel.org>
Cc: linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v2 09/22] media: rockchip: rga: align stride to 4 bytes

Hi,

Le mercredi 03 décembre 2025 à 16:52 +0100, Sven Püschel a écrit :
> Add an alignment setting to rga_hw to set the desired stride alignment.
> As the RGA2 register for the stride counts in word units, the code
> already divides the bytesperline value by 4 when writing it into the
> register. Therefore fix the alignment to a multiple of 4 to avoid
> potential off by one errors due from the division.

If you decide to keep the stride alignment to be width alignment, then please
make use struct v4l2_frmsize_stepwise and v4l2_apply_frmsize_constraints
instead.

It will also make the per-variant description a lot more clear, with the min/max
resolution exposed.

Nicolas

> 
> Signed-off-by: Sven Püschel <s.pueschel@...gutronix.de>
> ---
>  drivers/media/platform/rockchip/rga/rga-hw.c |  1 +
>  drivers/media/platform/rockchip/rga/rga.c    | 11 ++++++-----
>  drivers/media/platform/rockchip/rga/rga.h    |  1 +
>  3 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/platform/rockchip/rga/rga-hw.c b/drivers/media/platform/rockchip/rga/rga-hw.c
> index 79bf911e74779..56a2558539bfb 100644
> --- a/drivers/media/platform/rockchip/rga/rga-hw.c
> +++ b/drivers/media/platform/rockchip/rga/rga-hw.c
> @@ -620,6 +620,7 @@ const struct rga_hw rga2_hw = {
>  	.max_width = MAX_WIDTH,
>  	.min_height = MIN_HEIGHT,
>  	.max_height = MAX_HEIGHT,
> +	.stride_alignment = 4,
>  
>  	.start = rga_hw_start,
>  	.handle_irq = rga_handle_irq,
> diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
> index 74d94c7fe31ff..592c977a07cf3 100644
> --- a/drivers/media/platform/rockchip/rga/rga.c
> +++ b/drivers/media/platform/rockchip/rga/rga.c
> @@ -234,10 +234,10 @@ static int rga_open(struct file *file)
>  	ctx->in = def_frame;
>  	ctx->out = def_frame;
>  
> -	v4l2_fill_pixfmt_mp(&ctx->in.pix,
> -			    ctx->in.fmt->fourcc, def_width, def_height);
> -	v4l2_fill_pixfmt_mp(&ctx->out.pix,
> -			    ctx->out.fmt->fourcc, def_width, def_height);
> +	v4l2_fill_pixfmt_mp_aligned(&ctx->in.pix, ctx->in.fmt->fourcc,
> +				    def_width, def_height, rga->hw->stride_alignment);
> +	v4l2_fill_pixfmt_mp_aligned(&ctx->out.pix, ctx->out.fmt->fourcc,
> +				    def_width, def_height, rga->hw->stride_alignment);
>  
>  	if (mutex_lock_interruptible(&rga->mutex)) {
>  		ret = -ERESTARTSYS;
> @@ -359,7 +359,8 @@ static int vidioc_try_fmt(struct file *file, void *priv, struct v4l2_format *f)
>  	pix_fmt->height = clamp(pix_fmt->height,
>  				hw->min_height, hw->max_height);
>  
> -	v4l2_fill_pixfmt_mp(pix_fmt, fmt->fourcc, pix_fmt->width, pix_fmt->height);
> +	v4l2_fill_pixfmt_mp_aligned(pix_fmt, pix_fmt->pixelformat,
> +				    pix_fmt->width, pix_fmt->height, hw->stride_alignment);
>  	pix_fmt->field = V4L2_FIELD_NONE;
>  
>  	return 0;
> diff --git a/drivers/media/platform/rockchip/rga/rga.h b/drivers/media/platform/rockchip/rga/rga.h
> index f8c932fdec21a..0aef348dddb95 100644
> --- a/drivers/media/platform/rockchip/rga/rga.h
> +++ b/drivers/media/platform/rockchip/rga/rga.h
> @@ -152,6 +152,7 @@ struct rga_hw {
>  	size_t cmdbuf_size;
>  	u32 min_width, min_height;
>  	u32 max_width, max_height;
> +	u8 stride_alignment;
>  
>  	void (*start)(struct rockchip_rga *rga,
>  		      struct rga_vb_buffer *src, struct rga_vb_buffer *dst);

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