linux-kernel - Re: [PATCH v1 05/17] drm/mediatek: hdmi: use a syscon/regmap instead of iomem

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Date:   Tue, 20 Sep 2022 12:18:44 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Guillaume Ranquet <granquet@...libre.com>,
        Vinod Koul <vkoul@...nel.org>, Stephen Boyd <sboyd@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Rob Herring <robh+dt@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        CK Hu <ck.hu@...iatek.com>, Jitao shi <jitao.shi@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     linux-mediatek@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org,
        Pablo Sun <pablo.sun@...iatek.com>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mattijs Korpershoek <mkorpershoek@...libre.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v1 05/17] drm/mediatek: hdmi: use a syscon/regmap instead
 of iomem

Il 19/09/22 18:56, Guillaume Ranquet ha scritto:
> To prepare support for newer chips that need to share their address
> range with a dedicated ddc driver, move to a syscon.
> 
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_hdmi.c b/drivers/gpu/drm/mediatek/mtk_hdmi.c
> index 3196189429bc..5cd05d4fe1a9 100644
> --- a/drivers/gpu/drm/mediatek/mtk_hdmi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_hdmi.c

..snip..

> @@ -1428,7 +1413,6 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
>   	struct device_node *cec_np, *remote, *i2c_np;
>   	struct platform_device *cec_pdev;
>   	struct regmap *regmap;
> -	struct resource *mem;
>   	int ret;
>   
>   	ret = mtk_hdmi_get_all_clk(hdmi, np);
> @@ -1474,8 +1458,7 @@ static int mtk_hdmi_dt_parse_pdata(struct mtk_hdmi *hdmi,
>   	}
>   	hdmi->sys_regmap = regmap;
>   
> -	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -	hdmi->regs = devm_ioremap_resource(dev, mem);
> +	hdmi->regs = syscon_node_to_regmap(dev->of_node);

Nack. You're breaking ABI, this will force everyone to add syscon to devicetree,
hence this breaks retrocompatibility with old devicetrees.

Hint: not here, device_node_to_regmap()

Regards,
Angelo

>   	if (IS_ERR(hdmi->regs)) {
>   		ret = PTR_ERR(hdmi->regs);
>   		goto put_device;