linux-kernel - Re: [PATCH v2 2/2] media: i2c: ov02e10: add OV02E10 image sensor driver

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Message-ID: <47dd7daa-cce4-4ad0-ab57-4c76304b0aa6@linaro.org>
Date: Tue, 1 Apr 2025 01:34:29 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Bryan O'Donoghue <bod@...nel.org>,
 Hans de Goede <hansg@...nel.org>, Jingjing Xiong <jingjing.xiong@...el.com>,
 Hao Yao <hao.yao@...el.com>, Jim Lai <jim.lai@...el.com>,
 You-Sheng Yang <vicamo.yang@...onical.com>,
 Alan Stern <stern@...land.harvard.edu>, Hans de Goede <hdegoede@...hat.com>,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/2] media: i2c: ov02e10: add OV02E10 image sensor
 driver

On 27/03/2025 07:36, Sakari Ailus wrote:
>> +static u64 to_pixel_rate(u32 f_index)
>> +{
>> +	u64 pixel_rate = link_freq_menu_items[f_index] * 2 * OV02E10_DATA_LANES;
>> +
>> +	do_div(pixel_rate, OV02E10_RGB_DEPTH);
> The pixel rate control is for the pixel rate on the pixel array, not on the
> CSI-2 interface. Without binning or sub-sampling these may the same still,
> but this only works in special cases really.

Hmm computer says no, I don't think I have understood this comment..

Looking at other drivers, I'd say the above pattern is pretty common - 
taking ov8856 as an example that's pretty much equivalent logic to the 
above, ov08x40 does something similar.

=>

pixel_rate == link_freq * 2 * #oflanes / RGB_DEPTH
            => 360MHz * 2 * 2 / 10
            => 360000000 * 2 * 2 / 10
            => 144000000

If I'm understanding you though you mean the pixel rate for the control 
V4L2_CID_PIXEL_RATE expressed here should be the resolution * the FPS / 
bits_per_pixel

pixel_rate = wdith x height x fps / bpp
            => 1928 * 1088 * 30 / 10
            => 6292992

i.e. the pixel rate not related to the CSI2 link frequency ?

---
bod