Re: [linux-sunxi] [PATCH 01/14] phy: Distinguish between Rx and Tx for MIPI D-PHY with submodes

From: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
To: "Jernej Škrabec" <jernej.skrabec@gmail.com>
Cc: linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org,
	linux-sunxi@googlegroups.com,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Maxime Ripard <mripard@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
	Yong Deng <yong.deng@magewell.com>,
	Kishon Vijay Abraham I <kishon@ti.com>,
	Vinod Koul <vkoul@kernel.org>,
	Helen Koike <helen.koike@collabora.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Hans Verkuil <hans.verkuil@cisco.com>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Hans Verkuil <hverkuil@xs4all.nl>,
	kevin.lhopital@hotmail.com
Subject: Re: [linux-sunxi] [PATCH 01/14] phy: Distinguish between Rx and Tx for MIPI D-PHY with submodes
Date: Sat, 24 Oct 2020 10:31:21 +0200	[thread overview]
Message-ID: <20201024083121.GB1739@aptenodytes> (raw)
In-Reply-To: <7673189.jqQXtdQLJ6@kista>

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Hi Jernej,

On Fri 23 Oct 20, 20:18, Jernej Škrabec wrote:
> Dne petek, 23. oktober 2020 ob 19:45:33 CEST je Paul Kocialkowski napisal(a):
> > As some D-PHY controllers support both Rx and Tx mode, we need a way for
> > users to explicitly request one or the other. For instance, Rx mode can
> > be used along with MIPI CSI-2 while Tx mode can be used with MIPI DSI.
> > 
> > Introduce new MIPI D-PHY PHY submodes to use with PHY_MODE_MIPI_DPHY.
> > The default (zero value) is kept to Tx so only the rkisp1 driver, which
> > uses D-PHY in Rx mode, needs to be adapted.
> > 
> > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > ---
> >  drivers/staging/media/rkisp1/rkisp1-isp.c |  3 ++-
> >  include/linux/phy/phy-mipi-dphy.h         | 13 +++++++++++++
> 
> I think some changes are missing in this patch. For example, 
> phy_set_mode_ext() must be modified to take another argument, otherwise change 
> of rkisp1-isp driver doesn't make much sense.

Thanks for looking into this! As you can see in:
https://elixir.bootlin.com/linux/latest/source/include/linux/phy/phy.h#L213

phy_set_mode_ext already takes a submode argument (which is already used for
USB mode selection, for instance) and phy_set_mode is just a macro which calls
phy_set_mode_ext with submode set to 0.

In our case, that means that most current users of phy_set_mode with
PHY_MODE_MIPI_DPHY will select Tx mode by default, so there is no particular
need for adaptation. Only the rkisp1 driver uses PHY_MODE_MIPI_DPHY for Rx,
so this one was changed to use phy_set_mode_ext with PHY_MIPI_DPHY_SUBMODE_RX
instead.

As a result, there should be no missing changes. Do you agree?

Cheers,

Paul

> Best regards,
> Jernej
> 
> >  2 files changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/media/rkisp1/rkisp1-isp.c b/drivers/staging/
> media/rkisp1/rkisp1-isp.c
> > index 6ec1e9816e9f..0afbce00121e 100644
> > --- a/drivers/staging/media/rkisp1/rkisp1-isp.c
> > +++ b/drivers/staging/media/rkisp1/rkisp1-isp.c
> > @@ -902,7 +902,8 @@ static int rkisp1_mipi_csi2_start(struct rkisp1_isp 
> *isp,
> >  
> >  	phy_mipi_dphy_get_default_config(pixel_clock, isp->sink_fmt-
> >bus_width,
> >  					 sensor->lanes, cfg);
> > -	phy_set_mode(sensor->dphy, PHY_MODE_MIPI_DPHY);
> > +	phy_set_mode_ext(cdev->dphy, PHY_MODE_MIPI_DPHY,
> > +			 PHY_MIPI_DPHY_SUBMODE_RX);
> >  	phy_configure(sensor->dphy, &opts);
> >  	phy_power_on(sensor->dphy);
> >  
> > diff --git a/include/linux/phy/phy-mipi-dphy.h b/include/linux/phy/phy-mipi-
> dphy.h
> > index a877ffee845d..0f57ef46a8b5 100644
> > --- a/include/linux/phy/phy-mipi-dphy.h
> > +++ b/include/linux/phy/phy-mipi-dphy.h
> > @@ -6,6 +6,19 @@
> >  #ifndef __PHY_MIPI_DPHY_H_
> >  #define __PHY_MIPI_DPHY_H_
> >  
> > +/**
> > + * enum phy_mipi_dphy_submode - MIPI D-PHY sub-mode
> > + *
> > + * A MIPI D-PHY can be used to transmit or receive data.
> > + * Since some controllers can support both, the direction to enable is 
> specified
> > + * with the PHY sub-mode. Transmit is assumed by default with phy_set_mode.
> > + */
> > +
> > +enum phy_mipi_dphy_submode {
> > +	PHY_MIPI_DPHY_SUBMODE_TX = 0,
> > +	PHY_MIPI_DPHY_SUBMODE_RX,
> > +};
> > +
> >  /**
> >   * struct phy_configure_opts_mipi_dphy - MIPI D-PHY configuration set
> >   *
> > -- 
> > 2.28.0
> > 
> > -- 
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> linux-sunxi/20201023174546.504028-2-paul.kocialkowski%40bootlin.com.
> > 
> 
> 

-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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