linux-kernel - Re: [PATCH v11 1/1] phy: phy-mtk-dp: Add driver for DP phy

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Message-ID: <f6d8ad7cade15c2b0388d64f31bef47d73b7bec7.camel@mediatek.com>
Date:   Thu, 16 Jun 2022 15:00:12 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <chunkuang.hu@...nel.org>, <p.zabel@...gutronix.de>,
        <chunfeng.yun@...iatek.com>, <kishon@...com>, <vkoul@...nel.org>,
        <matthias.bgg@...il.com>, <airlied@...ux.ie>
CC:     <msp@...libre.com>, <granquet@...libre.com>,
        <jitao.shi@...iatek.com>, <wenst@...omium.org>,
        <ck.hu@...iatek.com>, <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-phy@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v11 1/1] phy: phy-mtk-dp: Add driver for DP phy

On Mon, 2022-06-13 at 12:39 +0200, AngeloGioacchino Del Regno wrote:
> Il 13/06/22 09:26, Bo-Chen Chen ha scritto:
> > From: Markus Schneider-Pargmann <msp@...libre.com>
> > 
> > This is a new driver that supports the integrated DisplayPort phy
> > for
> > mediatek SoCs, especially the mt8195. The phy is integrated into
> > the
> > DisplayPort controller and will be created by the mtk-dp driver.
> > This
> > driver expects a struct regmap to be able to work on the same
> > registers
> > as the DisplayPort controller. It sets the device data to be the
> > struct
> > phy so that the DisplayPort controller can easily work with it.
> > 
> > The driver does not have any devicetree bindings because the
> > datasheet
> > does not list the controller and the phy as distinct units.
> > 
> > The interaction with the controller can be covered by the configure
> > callback of the phy framework and its displayport parameters.
> > 
> > Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> > Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> > [Bo-Chen: Modify reviewers' comments.]
> > Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> 
> There's no power_on()/power_off() callbacks and looks a bit weird,
> but it's
> also right... the only thing that's missing, IMO, is a comment in the
> actual
> file explaining that power for this PHY is always on when the DP
> block is on
> and that no PHY specific power sequence has to be carried on (being
> managed
> elsewhere and strongly tied to the specific DP IP).
> 
> Besides that,
> 
> Reviewed-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@...labora.com>
> 

Hello Angelo,

there is no power-on/off setting register for dp-phy because of the
hardware design.

Therefore, we power-on/off using enable/disable power domain.
You can see the function mtk_dp_suspend/mtk_dp_resume in mtk-dp.c
"pm_runtime_get_sync/pm_runtime_put_sync".

When the power domain is disable, the phy is also diabled.

BRs,
Bo-Chen