linux-kernel - Re: [PATCH v15 05/11] drm/mediatek: Add MT8195 Embedded DisplayPort driver

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Date:   Tue, 2 Aug 2022 13:09:08 +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 v15 05/11] drm/mediatek: Add MT8195 Embedded DisplayPort
 driver

Hi, Bo-Chen:

On Wed, 2022-07-27 at 12:50 +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 irqreturn_t mtk_dp_hpd_event_thread(int hpd, void *dev)
> +{
> +	struct mtk_dp *mtk_dp = dev;
> +
> +	if (mtk_dp->train_info.hpd_inerrupt) {

When the thread is running, mtk_dp->train_info.hpd_inerrupt would be
true. So this checking is redundant.

> +		dev_dbg(mtk_dp->dev, "MTK_DP_HPD_INTERRUPT\n");
> +		mtk_dp->train_info.hpd_inerrupt = false;
> +		mtk_dp_hpd_sink_event(mtk_dp);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t mtk_dp_hpd_event(int hpd, void *dev)
> +{
> +	struct mtk_dp *mtk_dp = dev;
> +	struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
> +	u32 irq_status;
> +
> +	irq_status = mtk_dp_read(mtk_dp, MTK_DP_TOP_IRQ_STATUS);
> +
> +	if (!irq_status)
> +		return IRQ_HANDLED;
> +
> +	if (irq_status & RGS_IRQ_STATUS_TRANSMITTER) {

Combine this if-checking with previous if-checking, it would be:

if (!(irq_status & RGS_IRQ_STATUS_TRANSMITTER))
	return IRQ_HANDLED;

> +		irq_status = mtk_dp_swirq_get_clear(mtk_dp) |
> +			     mtk_dp_hwirq_get_clear(mtk_dp);
> +
> +		if (!irq_status)
> +			return IRQ_HANDLED;
> +
> +		if (irq_status & MTK_DP_HPD_INTERRUPT)

Does this interrupt MTK_DP_HPD_INTERRUPT have any relation with
MTK_DP_HPD_CONNECT and MTK_DP_HPD_CONNECT? From the naming, I guess
that when MTK_DP_HPD_CONNECT happen, MTK_DP_HPD_INTERRUPT would also
happen. Either for MTK_DP_HPD_DISCONNECT. When would
MTK_DP_HPD_INTERRUPT happen but MTK_DP_HPD_CONNECT or
MTK_DP_HPD_DISCONNECT does not happen.

Regards,
CK

> +			train_info->hpd_inerrupt = true;
> +
> +		if (!(irq_status & MTK_DP_HPD_CONNECT ||
> +		      irq_status & MTK_DP_HPD_DISCONNECT))
> +			return IRQ_WAKE_THREAD;
> +
> +		if (!!(mtk_dp_read(mtk_dp, MTK_DP_TRANS_P0_3414) &
> +		       HPD_DB_DP_TRANS_P0_MASK))
> +			train_info->cable_plugged_in = true;
> +		else
> +			train_info->cable_plugged_in = false;
> +
> +		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> +				   DP_PWR_STATE_BANDGAP_TPLL_LANE,
> +				   DP_PWR_STATE_MASK);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +