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

Paul Kocialkowski
2020-10-24T08:31:31Z

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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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> >
>
>

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

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