linux-kernel - Re: [PATCH v2 2/2] phy: mtk-mipi-csi: add driver for CSI phy

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Date:   Mon, 15 May 2023 16:07:07 +0200
From:   Julien Stephan <jstephan@...libre.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     krzysztof.kozlowski@...aro.org, robh@...nel.org,
        chunkuang.hu@...nel.org, linux-mediatek@...ts.infradead.org,
        Phi-bang Nguyen <pnguyen@...libre.com>,
        Louis Kuo <louis.kuo@...iatek.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Andy Hsieh <andy.hsieh@...iatek.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek USB3 PHY DRIVER" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:GENERIC PHY FRAMEWORK" <linux-phy@...ts.infradead.org>,
        "open list:DRM DRIVERS FOR MEDIATEK" 
        <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v2 2/2] phy: mtk-mipi-csi: add driver for CSI phy

On Mon, May 15, 2023 at 02:22:52PM +0200, AngeloGioacchino Del Regno wrote:
> > +#define CSIxB_OFFSET		0x1000
>
> What if we grab two (or three?) iospaces from devicetree?
>
> - base (global)
> - csi_a
> - csi_b
>
> That would make it possible to maybe eventually extend this driver to more
> versions (older or newer) of the CSI PHY IP without putting fixes offsets
> inside of platform data structures and such.
>
Hi Angelo,
The register bank of the CSI port is divided into 2:
* from base address to base + 0x1000 (port A)
* from base + 0x1000 to base +0x2000 (port B)
Some CSI port can be configured in 4D1C mode (4 data + 1 clock) using
the whole register bank from base to base + 0x2000 or in 2D1C mode (2 data +
1 clock) and use either port A or port B.

For example  mt8365 has CSI0 that can be used either in 4D1C mode or in
2 * 2D1C and CSI1 which can use only 4D1C mode

2D1C mode can not be tested and is not implemented in the driver so
I guess adding csi_a and csi_b reg value may be confusing?

What do you think?

Regards,
Julien