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

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Date:   Fri, 5 Aug 2022 16:22:58 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     CK Hu <ck.hu@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "mripard@...nel.org" <mripard@...nel.org>,
        "tzimmermann@...e.de" <tzimmermann@...e.de>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "deller@....de" <deller@....de>,
        "airlied@...ux.ie" <airlied@...ux.ie>
CC:     "msp@...libre.com" <msp@...libre.com>,
        "granquet@...libre.com" <granquet@...libre.com>,
        Jitao Shi (石记涛) 
        <jitao.shi@...iatek.com>,
        "wenst@...omium.org" <wenst@...omium.org>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>,
        LiangXu Xu (徐亮) 
        <LiangXu.Xu@...iatek.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        Project_Global_Chrome_Upstream_Group 
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v15 05/11] drm/mediatek: Add MT8195 Embedded DisplayPort
 driver

On Tue, 2022-08-02 at 13:09 +0800, CK Hu wrote:
> 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.
> 

Hello CK,

ok, I will remove it.

> > +		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;
> 

ok.

> > +		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.
> 

There is no relation for these status. They are individual.
MTK_DP_HPD_INTERRUPT is for interrupt from sink device. After receiving
this source device should do some actions.

MTK_DP_HPD_CONNECT and MTK_DP_HPD_DISCONNECT are for HPD status.

BRs,
Bo-Chen

> 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;
> > +}
> > +
> 
>