linux-kernel - Re: [EXT] Re: [PATCH v18 6/8] phy: freescale: Add DisplayPort/HDMI Combo-PHY driver for i.MX8MQ

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <CAA8EJprUKXxGbtP6M95Ep=2Lj2NSiUN31QNaysNJAzvO5g2LdQ@mail.gmail.com>
Date: Mon, 9 Dec 2024 12:13:15 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Sandor Yu <sandor.yu@....com>
Cc: "andrzej.hajda@...el.com" <andrzej.hajda@...el.com>, 
	"neil.armstrong@...aro.org" <neil.armstrong@...aro.org>, 
	Laurent Pinchart <laurent.pinchart@...asonboard.com>, "jonas@...boo.se" <jonas@...boo.se>, 
	"jernej.skrabec@...il.com" <jernej.skrabec@...il.com>, "airlied@...il.com" <airlied@...il.com>, 
	"daniel@...ll.ch" <daniel@...ll.ch>, "robh+dt@...nel.org" <robh+dt@...nel.org>, 
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>, 
	"shawnguo@...nel.org" <shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>, 
	"festevam@...il.com" <festevam@...il.com>, "vkoul@...nel.org" <vkoul@...nel.org>, 
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-phy@...ts.infradead.org" <linux-phy@...ts.infradead.org>, "mripard@...nel.org" <mripard@...nel.org>, 
	"kernel@...gutronix.de" <kernel@...gutronix.de>, dl-linux-imx <linux-imx@....com>, 
	Oliver Brown <oliver.brown@....com>, 
	"alexander.stein@...tq-group.com" <alexander.stein@...tq-group.com>, "sam@...nborg.org" <sam@...nborg.org>
Subject: Re: [EXT] Re: [PATCH v18 6/8] phy: freescale: Add DisplayPort/HDMI
 Combo-PHY driver for i.MX8MQ

On Mon, 9 Dec 2024 at 10:16, Sandor Yu <sandor.yu@....com> wrote:
>
>
>
> > -----Original Message-----
> > From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > Sent: 2024年11月30日 16:30
> > To: Sandor Yu <sandor.yu@....com>
> > Cc: andrzej.hajda@...el.com; neil.armstrong@...aro.org; Laurent Pinchart
> > <laurent.pinchart@...asonboard.com>; jonas@...boo.se;
> > jernej.skrabec@...il.com; airlied@...il.com; daniel@...ll.ch;
> > robh+dt@...nel.org; krzysztof.kozlowski+dt@...aro.org;
> > shawnguo@...nel.org; s.hauer@...gutronix.de; festevam@...il.com;
> > vkoul@...nel.org; dri-devel@...ts.freedesktop.org;
> > devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> > linux-kernel@...r.kernel.org; linux-phy@...ts.infradead.org;
> > mripard@...nel.org; kernel@...gutronix.de; dl-linux-imx
> > <linux-imx@....com>; Oliver Brown <oliver.brown@....com>;
> > alexander.stein@...tq-group.com; sam@...nborg.org
> > Subject: Re: [EXT] Re: [PATCH v18 6/8] phy: freescale: Add DisplayPort/HDMI
> > Combo-PHY driver for i.MX8MQ
> >
> > Caution: This is an external email. Please take care when clicking links or
> > opening attachments. When in doubt, report the message using the 'Report
> > this email' button
> >
> >
> > On Tue, Nov 26, 2024 at 02:12:19PM +0000, Sandor Yu wrote:
> > >
> > > >
> > > > On Tue, Nov 05, 2024 at 02:05:51PM +0000, Sandor Yu wrote:
> > > > > >
> > > > > > On Tue, Oct 29, 2024 at 02:02:14PM +0800, Sandor Yu wrote:
> > > > > > > Add Cadence HDP-TX DisplayPort and HDMI PHY driver for
> > i.MX8MQ.
> > > > > > >
> > > > > > > Cadence HDP-TX PHY could be put in either DP mode or HDMI mode
> > > > > > > base on the configuration chosen.
> > > > > > > DisplayPort or HDMI PHY mode is configured in the driver.
> > > > > > >
> > > > > > > Signed-off-by: Sandor Yu <Sandor.yu@....com>
> > > > > > > Signed-off-by: Alexander Stein
> > > > > > > <alexander.stein@...tq-group.com>
> > > > > > > ---
> > > > > > > v17->v18:
> > > > > > > - fix build error as code rebase to latest kernel version.
> > > > > > >
> > > > > > >  drivers/phy/freescale/Kconfig                |   10 +
> > > > > > >  drivers/phy/freescale/Makefile               |    1 +
> > > > > > >  drivers/phy/freescale/phy-fsl-imx8mq-hdptx.c | 1337
> > > > > > ++++++++++++++++++
> > > > > > >  3 files changed, 1348 insertions(+)  create mode 100644
> > > > > > > drivers/phy/freescale/phy-fsl-imx8mq-hdptx.c
> > > > > > >
> > > > > > > diff --git a/drivers/phy/freescale/Kconfig
> > > > > > > b/drivers/phy/freescale/Kconfig index
> > > > > > > dcd9acff6d01a..2b1210367b31c
> > > > > > > 100644
> > > > > > > --- a/drivers/phy/freescale/Kconfig
> > > > > > > +++ b/drivers/phy/freescale/Kconfig
> > > >
> > > > [...]
> > > >
> > > > I'm sorry, my email client cut the email.
> > > >
> > > > > > > +static int cdns_hdptx_dp_configure(struct phy *phy,
> > > > > > > +                                union phy_configure_opts
> > > > *opts) {
> > > > > > > +     struct cdns_hdptx_phy *cdns_phy = phy_get_drvdata(phy);
> > > > > > > +
> > > > > > > +     cdns_phy->dp.link_rate = opts->dp.link_rate;
> > > > > > > +     cdns_phy->dp.lanes = opts->dp.lanes;
> > > > > >
> > > > > > Shouldn't this be conditional on set_rate / set_lanes ?
> > > > >
> > > > > PHY do not support reconfigure link rate and lane count.
> > > >
> > > > So, you don't support reconfiguring the rate / count, but you still
> > > > copy the new rate and lanes into your driver data. That sounds strange.
> > >
> > > The PHY will use link rate and lane count to configure its registers
> >
> > I'm not sure if I follow it. Do you mean that rate / count configuration is static?
>
> In DP controller driver, rate and lane count are determined during link training.
> These two parameters are fixed in the DP PHY driver and cannot be modified.

Yes, llane count, rate and swing are determined during link training.
However it's not a part of the PHY's job to settle on that. Usually it
is the DP driver who determines these params and then calls
phy_configure() to set necessary params for the next iteration of
clock recovery attempt or link training step. As a part of the calling
API the DP driver doesn't have to pass full configuration. Instead DP
driver sets only required parts of the PHY configuration and uses
these flags to specify which part of the PHY configuration should be
updated and which parts were not set and must be ignored.

-- 
With best wishes
Dmitry