linux-kernel - Re: [PATCH v11 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

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Message-ID: <b3d5ba22e0a88abb48261a6a97027361fc535fc6.camel@mediatek.com>
Date:   Wed, 15 Jun 2022 13:53:25 +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 v11 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort
 driver

Hi, Bo-Chen:

On Fri, 2022-06-10 at 18:55 +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 int mtk_dp_train_set_pattern(struct mtk_dp *mtk_dp, int
> pattern)
> +{
> +	if (pattern < 0 || pattern > 4) {

The caller would pass pattern from 0 to 4, so this checking is
redundant. Remove it and this function would always return true, so let
this function be void.

Regards,
CK

> +		drm_err(mtk_dp->drm_dev,
> +			"Implementation error, no such pattern %d\n",
> pattern);
> +		return -EINVAL;
> +	}
> +
> +	/* TPS1 */
> +	if (pattern == 1)
> +		mtk_dp_set_idle_pattern(mtk_dp, false);
> +
> +	mtk_dp_update_bits(mtk_dp,
> +			   MTK_DP_TRANS_P0_3400,
> +			   pattern ?
> +			   BIT(pattern - 1) <<
> PATTERN1_EN_DP_TRANS_P0_SHIFT :
> +			   0,
> +			   PATTERN1_EN_DP_TRANS_P0_MASK |
> +			   PATTERN2_EN_DP_TRANS_P0_MASK |
> +			   PATTERN3_EN_DP_TRANS_P0_MASK |
> +			   PATTERN4_EN_DP_TRANS_P0_MASK);
> +	return 0;
> +}