linux-kernel - Re: [PATCH v12 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

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Message-ID: <795ff1c78743f2345c9036b1b96966d238be0482.camel@mediatek.com>
Date:   Wed, 29 Jun 2022 12:54:44 +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>,
        <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 v12 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort
 driver

Hi, Bo-Chen:

On Mon, 2022-06-27 at 16:03 +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>
> [Bo-Chen: Cleanup the drivers and modify comments from reviewers]
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> ---

[snip]

> +
> +static void mtk_dp_setup_tu(struct mtk_dp *mtk_dp)
> +{
> +	u32 sram_read_start = MTK_DP_TBC_BUF_READ_START_ADDR;

This initial value is redundant. So remove this initial value.

> +
> +	if (mtk_dp->train_info.lane_count > 0) {

This checking would always be true.
This function would be called after training success, so mtk_dp-
>train_info.lane_count would be greater than 0.
So remove this checking.

Regards,
CK

> +		sram_read_start = min_t(u32,
> +					MTK_DP_TBC_BUF_READ_START_ADDR,
> +					mtk_dp->info.timings.vm.hactive 
> /
> +					mtk_dp->train_info.lane_count /
> +					MTK_DP_4P1T / MTK_DP_HDE /
> MTK_DP_PIX_PER_ADDR);
> +		mtk_dp_set_sram_read_start(mtk_dp, sram_read_start);
> +	}
> +
> +	mtk_dp_setup_encoder(mtk_dp);
> +}
> +