linux-kernel - Re: [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

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Message-ID: <9eceb5412bfed5f408153fe05bc2f8a4e3570b77.camel@mediatek.com>
Date:   Wed, 13 Jul 2022 17:31:02 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Bo-Chen Chen <rex-bc.chen@...iatek.com>, <chunkuang.hu@...nel.org>,
        <p.zabel@...gutronix.de>, <daniel@...ll.ch>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <mripard@...nel.org>,
        <tzimmermann@...e.de>, <matthias.bgg@...il.com>, <deller@....de>,
        <airlied@...ux.ie>
CC:     <msp@...libre.com>, <granquet@...libre.com>,
        <jitao.shi@...iatek.com>, <wenst@...omium.org>,
        <angelogioacchino.delregno@...labora.com>,
        <liangxu.xu@...iatek.com>, <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-fbdev@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort
 driver

Hi, Bo-Chen:

On Tue, 2022-07-12 at 19:12 +0800, Bo-Chen Chen wrote:
> From: Markus Schneider-Pargmann <msp@...libre.com>
> 
> This patch adds a embedded displayport driver for the MediaTek mt8195
> SoC.
> 
> It supports the MT8195, the embedded DisplayPort units. It offers
> DisplayPort 1.4 with up to 4 lanes.
> 
> The driver creates a child device for the phy. The child device will
> never exist without the parent being active. As they are sharing a
> register range, the parent passes a regmap pointer to the child so
> that
> both can work with the same register range. The phy driver sets
> device
> data that is read by the parent to get the phy device that can be
> used
> to control the phy properties.
> 
> This driver is based on an initial version by
> Jitao shi <jitao.shi@...iatek.com>
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> ---

[snip]

> +
> +static void mtk_dp_bulk_16bit_write(struct mtk_dp *mtk_dp, u32
> offset, u8 *buf,
> +				    size_t length)

The offset would always be MTK_DP_AUX_P0_3708, so drop offset and use
MTK_DP_AUX_P0_3708 directly.

> +{
> +	int i;
> +	int num_regs = (length + 1) / 2;
> +
> +	/* 2 bytes per register */
> +	for (i = 0; i < num_regs; i++) {
> +		u32 val = buf[i * 2] |
> +			  (i * 2 + 1 < length ? buf[i * 2 + 1] << 8 :
> 0);
> +
> +		if (mtk_dp_write(mtk_dp, offset + i * 4, val))
> +			return;
> +	}

for (i = 0; i < length; i += 2) {
	val = buf[i] | (i + 1 < length ? buf[i + 1] << 8 : 0);
	if (mtk_dp_write(mtk_dp, MTK_DP_AUX_P0_3708 + i * 2, val))
		return;
}

Regards,
CK

> +}
> +