linux-kernel - Re: [PATCH v8 3/6] staging: media: Add support for the Allwinner A31 ISP

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Date:   Sun, 06 Nov 2022 10:12:22 +0100
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v8 3/6] staging: media: Add support for the Allwinner A31 ISP

Dne četrtek, 03. november 2022 ob 17:37:14 CET je Paul Kocialkowski 
napisal(a):
> Some Allwinner platforms come with an Image Signal Processor, which
> supports various features in order to enhance and transform data
> received by image sensors into good-looking pictures. In most cases,
> the data is raw bayer, which gets internally converted to RGB and
> finally YUV, which is what the hardware produces.
> 
> This driver supports ISPs that are similar to the A31 ISP, which was
> the first standalone ISP found in Allwinner platforms. Simpler ISP
> blocks were found in the A10 and A20, where they are tied to a CSI
> controller. Newer generations of Allwinner SoCs (starting with the
> H6, H616, etc) come with a new camera subsystem and revised ISP.
> Even though these previous and next-generation ISPs are somewhat
> similar to the A31 ISP, they have enough significant differences to
> be out of the scope of this driver.
> 
> While the ISP supports many features, including 3A and many
> enhancement blocks, this implementation is limited to the following:
> - V3s (V3/S3) platform support;
> - Bayer media bus formats as input;
> - Semi-planar YUV (NV12/NV21) as output;
> - Debayering with per-component gain and offset configuration;
> - 2D noise filtering with configurable coefficients.
> 
> Since many features are missing from the associated uAPI, the driver
> is aimed to integrate staging until all features are properly
> described.
> 
> On the technical side, it uses the v4l2 and media controller APIs,
> with a video node for capture, a processor subdev and a video node
> for parameters submission. A specific uAPI structure and associated
> v4l2 meta format are used to configure parameters of the supported
> modules.
> 
> One particular thing about the hardware is that configuration for
> module registers needs to be stored in a DMA buffer and gets copied
> to actual registers by the hardware at the next vsync, when instructed
> by a flag. This is handled by the "state" mechanism in the driver.
> 
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>

This is pretty complex piece of code, so I trust you that it's tested.

Acked-by: Jernej Skrabec <jernej.skrabec@...il.com>

Best regards,
Jernej