linux-kernel - Re: [PATCH v2 04/11] drm/mediatek: Add OVL compatible name for MT8195

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Date:   Wed, 11 Oct 2023 13:51:57 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>,
        CK Hu (胡俊光) <ck.hu@...iatek.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "wenst@...omium.org" <wenst@...omium.org>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "airlied@...il.com" <airlied@...il.com>
Subject: Re: [PATCH v2 04/11] drm/mediatek: Add OVL compatible name for MT8195

Il 11/10/23 11:38, Shawn Sung (宋孝謙) ha scritto:
> Hi, Angelo and CK,
> 
> On Mon, 2023-09-18 at 11:21 +0200, AngeloGioacchino Del Regno wrote:
>> Il 18/09/23 11:09, CK Hu (胡俊光) ha scritto:
>>> On Mon, 2023-09-18 at 16:42 +0800, Hsiao Chien Sung wrote:
>>>> Add OVL compatible name for MT8195.
>>>
>>> Reviewed-by: CK Hu <ck.hu@...iatek.com>
>>>
>>> but it's weird to put this patch into IGT series. Without this
>>> patch,
>>> mt8195 drm driver does not work not only IGT.
>>>
>>
>> The driver does work because the devicetree node declares two
>> compatibles,
>> "mediatek,mt8195-disp-ovl", "mediatek,mt8183-disp-ovl" where the
>> second
>> compatible is matched in mtk_drm_drv, and the first is matched in
>> mtk_disp_ovl
>> as both are platform_driver.
>>
>> This commit is not necessary, even... :-)
>>
>> Regards,
>> Angelo
>>
>>> Regards,
>>> CK
>>>
>>>>
>>>> Signed-off-by: Hsiao Chien Sung <shawn.sung@...iatek.com>
>>>> ---
>>>>    drivers/gpu/drm/mediatek/mtk_drm_drv.c | 2 ++
>>>>    1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>>> b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>>> index 93552d76b6e7..7759a06e5c0e 100644
>>>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>>> @@ -715,6 +715,8 @@ static const struct of_device_id
>>>> mtk_ddp_comp_dt_ids[] = {
>>>>    	  .data = (void *)MTK_DISP_OVL },
>>>>    	{ .compatible = "mediatek,mt8192-disp-ovl",
>>>>    	  .data = (void *)MTK_DISP_OVL },
>>>> +	{ .compatible = "mediatek,mt8195-disp-ovl",
>>>> +	  .data = (void *)MTK_DISP_OVL },
>>>>    	{ .compatible = "mediatek,mt8183-disp-ovl-2l",
>>>>    	  .data = (void *)MTK_DISP_OVL_2L },
>>>>    	{ .compatible = "mediatek,mt8192-disp-ovl-2l",
>>
>>
> 
> Please refer to c6aa5f1fb505. This is the main reason why we have to
> use MT8195 instead of MT8183/MT8192. Most of the formats required by
> IGT is not supported.
> 
> Without this commit, DRM won't work after changing the compatible name
> of ovl0 to "mediatek,mt8195-disp-ovl" in the dts.
> 
> Thanks,
> Shawn

You don't have to change anything at all in the dts.

The current mt8195.dtsi declares:
compatible = "mediatek,mt8195-disp-ovl", "mediatek,mt8183-disp-ovl";

..this is enough to get the mediatek,mt8195-disp-ovl match in mtk_disp_ovl.

Regards,
Angelo