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

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Message-ID: <33f121fa1a97e9fa8fd3fc6e87f197b7965bd825.camel@mediatek.com>
Date:   Fri, 1 Jul 2022 13:17:58 +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>,
        "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 v12 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort
 driver

On Wed, 2022-06-29 at 13:34 +0800, CK Hu wrote:
> 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_power_enable(struct mtk_dp *mtk_dp)
> > +{
> > +	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_RESET_AND_PROBE,
> > +			   0, SW_RST_B_PHYD);
> > +
> > +	/* Wait for power enable */
> > +	usleep_range(10, 200);
> > +
> > +	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_RESET_AND_PROBE,
> > +			   SW_RST_B_PHYD, SW_RST_B_PHYD);
> > +	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> > +			   DP_PWR_STATE_BANDGAP_TPLL,
> > DP_PWR_STATE_MASK);
> > +}
> > +
> > +static void mtk_dp_power_disable(struct mtk_dp *mtk_dp)
> > +{
> > +	mtk_dp_write(mtk_dp, MTK_DP_TOP_PWR_STATE, 0);
> > +
> > +	mtk_dp_write(mtk_dp, MTK_DP_0034,
> > +		     DA_CKM_CKTX0_EN_FORCE_EN |
> > +		     DA_CKM_BIAS_LPF_EN_FORCE_VAL |
> > +		     DA_CKM_BIAS_EN_FORCE_VAL |
> > +		     DA_XTP_GLB_LDO_EN_FORCE_VAL |
> > +		     DA_XTP_GLB_AVD10_ON_FORCE_VAL);
> > +
> > +	/* Disable RX */
> > +	mtk_dp_write(mtk_dp, MTK_DP_1040, 0);
> 
> MTK_DP_1040 is set to 0 in mtk_dp_power_disable(), but it is not set
> to
> other value in mtk_dp_power_enable(). Does any thing would be wrong
> when mtk_dp_power_disable() and mtk_dp_power_enable()?
> 
> Regards,
> CK
> 

Hello CK,

in mtk_dp_power_enable(),
after we reset the hw:
mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_RESET_AND_PROBE,
		   SW_RST_B_PHYD, SW_RST_B_PHYD);
mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
		   DP_PWR_STATE_BANDGAP_TPLL,
		   DP_PWR_STATE_MASK);

the value will be set back to default value 0x7.
I will add "mtk_dp_write(mtk_dp, MTK_DP_1040, 7);" to prevent
misunderstanding.

BRs,
Bo-Chen

> > +	mtk_dp_write(mtk_dp, MTK_DP_TOP_MEM_PD,
> > +		     0x550 | BIT(FUSE_SEL_SHIFT) |
> > BIT(MEM_ISO_EN_SHIFT));
> > +}
> > +
> 
>