linux-kernel - Re: [PATCH v4 07/17] phy: phy-rockchip-samsung-hdptx: Add support for eDP mode

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Message-ID: <pffzxwsqwkklur3b7c7hp6g5wonzam5fs35fwblil3cjfofozk@clwgt5gcb32a>
Date: Tue, 7 Jan 2025 12:55:03 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Damon Ding <damon.ding@...k-chips.com>
Cc: heiko@...ech.de, robh@...nel.org, krzk+dt@...nel.org, 
	conor+dt@...nel.org, rfoss@...nel.org, vkoul@...nel.org, 
	sebastian.reichel@...labora.com, cristian.ciocaltea@...labora.com, l.stach@...gutronix.de, 
	andy.yan@...k-chips.com, hjc@...k-chips.com, algea.cao@...k-chips.com, 
	kever.yang@...k-chips.com, dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-phy@...ts.infradead.org
Subject: Re: [PATCH v4 07/17] phy: phy-rockchip-samsung-hdptx: Add support
 for eDP mode

On Tue, Jan 07, 2025 at 11:02:15AM +0800, Damon Ding wrote:
> Hi Dmitry,
> 
> On 2024/12/30 20:45, Dmitry Baryshkov wrote:
> > On Thu, Dec 26, 2024 at 02:33:03PM +0800, Damon Ding wrote:
> > > Add basic support for RBR/HBR/HBR2 link rates, and the voltage swing and
> > > pre-emphasis configurations of each link rate have been verified according
> > > to the eDP 1.3 requirements.
> > 
> > Well... Please describe what's happening here. That the HDMI PHY on your
> > platform also provides support for DP / eDP. Please document any design
> > decisions that you had to make.
> > 
> 
> Yes, I will add more relevant descriptions in the next version.
> 
> > > 
> > > Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
> > > 
> > > ---
> > > 
> > > Changes in v2:
> > > - Add the module author
> > > 
> > > Changes in v3:
> > > - Split this patch into two, one for correction and the other for
> > >    extension
> > > 
> > > Changes in v4:
> > > - Add link_rate and lanes parameters in struct rk_hdptx_phy to store the
> > >    phy_configure() result for &phy_configure_opts.dp.link_rate and
> > >    &phy_configure_opts.dp.lanes
> > > ---
> > >   .../phy/rockchip/phy-rockchip-samsung-hdptx.c | 896 +++++++++++++++++-
> > >   1 file changed, 889 insertions(+), 7 deletions(-)
> > > 
> > > @@ -933,9 +1484,339 @@ static int rk_hdptx_phy_power_off(struct phy *phy)
> > >   	return rk_hdptx_phy_consumer_put(hdptx, false);
> > >   }
> > > +static int rk_hdptx_phy_set_mode(struct phy *phy, enum phy_mode mode,
> > > +				 int submode)
> > > +{
> > > +	return 0;
> > > +}
> > 
> > No need for the stub, please drop it. The host controller driver can
> > still call phy_set_mode() / _ext(), the call will return 0.
> 
> Without the &phy_ops.set_mode(), the phy driver can not get phy_mode to
> distinguish between HDMI and DP mode via the phy_get_mode(), even if the
> host driver calls phy_set_mode() / _ext(). Additionally, the previous
> discussion [0] also mentioned future considerations for dynamic switching.
> Indeed, I should add a related comment before the 'return 0;' to enhance
> understandability.

Oh... I see. Without .set_mode() callback the attrs.mode won't change.
We should probably fix that, there should be no need to add dummy stubs.


-- 
With best wishes
Dmitry