Re: [PATCH 03/16] media: rockchip: rga: align stride to 16 bytes

Hi Nicolas,

On 10/7/25 8:19 PM, Nicolas Dufresne wrote:

Hi,


Le mardi 07 octobre 2025 à 10:31 +0200, Sven Püschel a écrit :

quoted

Align the stride to a multiple of 16 according to the RGA3 requirements
mentioned in the datasheet. This also ensures that the stride of the RGA2
is aligned to 4 bytes, as it needs to divide the value by 4 (one word)
before storing it in the register.

Increasing the stride for the alignment also requires to increase the
sizeimage value. This is usually handled by v4l2_fill_pixfmt_mp, but
it doesn't allow to set a stride alignment. Therefore use the generated
values to calculate the total number of lines to properly update the
sizeimage value after the bytesperline has been aligned.

Signed-off-by: Sven Püschel <redacted>
---
  drivers/media/platform/rockchip/rga/rga.c | 21 +++++++++++++++++++++
  1 file changed, 21 insertions(+)

diff --git a/drivers/media/platform/rockchip/rga/rga.c

b/drivers/media/platform/rockchip/rga/rga.c
index
6438119a6c7aeff1e89e7aa95dcd5d2921fefa08..3cb7ce470c47e39d694e8176875a75fad271
7f96 100644

--- a/drivers/media/platform/rockchip/rga/rga.c
+++ b/drivers/media/platform/rockchip/rga/rga.c

@@ -459,6 +459,25 @@ static int vidioc_enum_fmt(struct file *file, void *priv,

struct v4l2_fmtdesc *f
  	return 0;
  }
  
+static void align_pixfmt(struct v4l2_pix_format_mplane *pix_fmt)
+{
+	int lines;
+	struct v4l2_plane_pix_format *fmt;
+
+	/*
+	 * Align stride to 16 for the RGA3 (based on the datasheet)
+	 * To not dismiss the v4l2_fill_pixfmt_mp helper
+	 * (and manually write it again), we're approximating the new
sizeimage
+	 */
+	for (fmt = pix_fmt->plane_fmt;
+	     fmt < pix_fmt->plane_fmt + pix_fmt->num_planes;
+	     fmt++) {
+		lines = DIV_ROUND_UP(fmt->sizeimage, fmt->bytesperline);
+		fmt->bytesperline = (fmt->bytesperline + 0xf) & ~0xf;
+		fmt->sizeimage = fmt->bytesperline * lines;

Instead of open coding this, describe this with struct v4l2_frmsize_stepwise and
then use v4l2_apply_frmsize_constraints().

Looking into v4l2_frmsize_stepwise, it only applies to the width/height 
values, whereas I'm interested to control the stride 
byte-alignment/stepping (allowing free range widths/heights).

Do you intent that I (mis)use it like this: 
v4l2_apply_frmsize_constraints(&fmt->bytesperline, &lines, &constraints)  ?

This only replaces one of the three lines in the for loop (where i 
manually do the alignment with & ~0xf) and would also look odd, as i use 
a value in bytes as a width parameter (expected to be in pixels).

Technically the core problem is that the v4l2_fill_pixfmt_mp helper 
doesn't allow to specify a stride byte alignment and just aligns the 
stride based on the format requirements. Therefore I think that maybe 
creating a new v4l2_fill_pixfmt_mp_aligned helper would probably be the 
better solution to get the correct bytesperline value right from the 
start instead of adjusting it afterwards.

Sincerely
     Sven

Nicolas

quoted

+	}
+}
+
  static int vidioc_g_fmt(struct file *file, void *priv, struct v4l2_format *f)
  {
  	struct v4l2_pix_format_mplane *pix_fmt = &f->fmt.pix_mp;

@@ -474,6 +493,7 @@ static int vidioc_g_fmt(struct file *file, void *priv,

struct v4l2_format *f)
  		return PTR_ERR(frm);
  
  	v4l2_fill_pixfmt_mp(pix_fmt, frm->fmt->fourcc, frm->width, frm-

quoted

height);

+	align_pixfmt(pix_fmt);
  
  	pix_fmt->field = V4L2_FIELD_NONE;
  	pix_fmt->colorspace = frm->colorspace;

@@ -496,6 +516,7 @@ static int vidioc_try_fmt(struct file *file, void *priv,

struct v4l2_format *f)
  				(u32)MIN_HEIGHT, (u32)MAX_HEIGHT);
  
  	v4l2_fill_pixfmt_mp(pix_fmt, fmt->fourcc, pix_fmt->width, pix_fmt-

quoted

height);

+	align_pixfmt(pix_fmt);
  	pix_fmt->field = V4L2_FIELD_NONE;
  
  	return 0;