linux-kernel - Re: [PATCH v5 01/14] media: ti: j721e-csi2rx: Remove word size alignment on frame width

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Message-ID: <023cb278-9002-442c-bcfd-eac790024d0b@ti.com>
Date: Mon, 8 Sep 2025 13:51:16 +0530
From: Rishikesh Donadkar <r-donadkar@...com>
To: Jai Luthra <jai.luthra@...asonboard.com>, <jai.luthra@...ux.dev>,
        <laurent.pinchart@...asonboard.com>, <mripard@...nel.org>
CC: <y-abhilashchandra@...com>, <devarsht@...com>, <vaishnav.a@...com>,
        <s-jain1@...com>, <vigneshr@...com>, <mchehab@...nel.org>,
        <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
        <sakari.ailus@...ux.intel.com>, <hverkuil-cisco@...all.nl>,
        <tomi.valkeinen@...asonboard.com>, <changhuang.liang@...rfivetech.com>,
        <jack.zhu@...rfivetech.com>, <linux-kernel@...r.kernel.org>,
        <linux-media@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 01/14] media: ti: j721e-csi2rx: Remove word size
 alignment on frame width


On 05/09/25 16:37, Jai Luthra wrote:
> Hi Rishikesh,


Hi Jai,

Thank you for the comments


>
> Quoting Rishikesh Donadkar (2025-08-25 19:55:09)
>> j721e-csi2rx driver has a limitation of frame width being a multiple
>> word size. However, there is no such limitation imposed by the
>> hardware [1].
> Is there no limitation for the step size, or also not limitation for the
> minimum size of transfer?



I did not see any mention of restrictions on the step size and minimum 
size of transfer in the TRM and the CSI functional specifications.


>
>> Remove this limitation from the driver.
>>
>> Link: https://www.ti.com/lit/pdf/spruj16
>> Signed-off-by: Rishikesh Donadkar <r-donadkar@...com>
>> ---
>>   .../platform/ti/j721e-csi2rx/j721e-csi2rx.c     | 17 +++--------------
>>   1 file changed, 3 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> index 3992f8b754b7..b3a27f4c3210 100644
>> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> @@ -260,9 +260,6 @@ static void ti_csi2rx_fill_fmt(const struct ti_csi2rx_fmt *csi_fmt,
>>                               MAX_WIDTH_BYTES * 8 / csi_fmt->bpp);
> Here the pix->width is restricted to be at minimum pixels_in_word.
> So TRY_FMT/S_FMT with a width = 1 will be clamped by the driver.
>
>>          pix->height = clamp_t(unsigned int, pix->height, 1, MAX_HEIGHT_LINES);
>>   
>> -       /* Width should be a multiple of transfer word-size */
>> -       pix->width = rounddown(pix->width, pixels_in_word);
>> -
>>          v4l2_fmt->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
>>          pix->pixelformat = csi_fmt->fourcc;
>>          pix->bytesperline = pix->width * (csi_fmt->bpp / 8);
>> @@ -360,23 +357,15 @@ static int ti_csi2rx_enum_framesizes(struct file *file, void *fh,
>>                                       struct v4l2_frmsizeenum *fsize)
>>   {
>>          const struct ti_csi2rx_fmt *fmt;
>> -       unsigned int pixels_in_word;
>>   
>>          fmt = find_format_by_fourcc(fsize->pixel_format);
>>          if (!fmt || fsize->index != 0)
>>                  return -EINVAL;
>>   
>> -       /*
>> -        * Number of pixels in one PSI-L word. The transfer happens in multiples
>> -        * of PSI-L word sizes.
>> -        */
>> -       pixels_in_word = PSIL_WORD_SIZE_BYTES * 8 / fmt->bpp;
>> -
>>          fsize->type = V4L2_FRMSIZE_TYPE_STEPWISE;
>> -       fsize->stepwise.min_width = pixels_in_word;
>> -       fsize->stepwise.max_width = rounddown(MAX_WIDTH_BYTES * 8 / fmt->bpp,
>> -                                             pixels_in_word);
>> -       fsize->stepwise.step_width = pixels_in_word;
>> +       fsize->stepwise.min_width = 1;
> But here, in ENUM_FRAMESIZES we allow width to go as low as 1.
>
> Can you make sure both of them match whatever is correct (and possible by
> the hardware)?


Sure


>
>> +       fsize->stepwise.max_width = MAX_WIDTH_BYTES * 8 / fmt->bpp;
>> +       fsize->stepwise.step_width = 1;
>>          fsize->stepwise.min_height = 1;
>>          fsize->stepwise.max_height = MAX_HEIGHT_LINES;
>>          fsize->stepwise.step_height = 1;
>> -- 
>> 2.34.1
>>
> Thanks,
>      Jai


Regards,

Rishikesh