linux-kernel - Re: [PATCH 2/4] phy: Add LVDS configuration options

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Message-ID: <c0077d1152adf2110cdbcf3f0b3e7fa20ad8256c.camel@nxp.com>
Date:   Wed, 09 Dec 2020 09:20:40 +0800
From:   Liu Ying <victor.liu@....com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, kishon@...com,
        vkoul@...nel.org, robh+dt@...nel.org, a.hajda@...sung.com,
        narmstrong@...libre.com, jonas@...boo.se, jernej.skrabec@...l.net,
        airlied@...ux.ie, daniel@...ll.ch, shawnguo@...nel.org,
        s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, agx@...xcpu.org, robert.chiras@....com,
        martin.kepplinger@...i.sm
Subject: Re: [PATCH 2/4] phy: Add LVDS configuration options

Hi Laurent,

On Tue, 2020-12-08 at 14:38 +0200, Laurent Pinchart wrote:
> Hi Liu,
> 
> Thank you for the patch.
> 
> On Fri, Dec 04, 2020 at 03:33:42PM +0800, Liu Ying wrote:
> > This patch allows LVDS PHYs to be configured through
> > the generic functions and through a custom structure
> > added to the generic union.
> > 
> > The parameters added here are based on common LVDS PHY
> > implementation practices.  The set of parameters
> > should cover all potential users.
> > 
> > Cc: Kishon Vijay Abraham I <kishon@...com>
> > Cc: Vinod Koul <vkoul@...nel.org>
> > Cc: NXP Linux Team <linux-imx@....com>
> > Signed-off-by: Liu Ying <victor.liu@....com>
> > ---
> >  include/linux/phy/phy-lvds.h | 48 ++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/phy/phy.h      |  4 ++++
> >  2 files changed, 52 insertions(+)
> >  create mode 100644 include/linux/phy/phy-lvds.h
> > 
> > diff --git a/include/linux/phy/phy-lvds.h b/include/linux/phy/phy-lvds.h
> > new file mode 100644
> > index 00000000..1b5b9d6
> > --- /dev/null
> > +++ b/include/linux/phy/phy-lvds.h
> > @@ -0,0 +1,48 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright 2020 NXP
> > + */
> > +
> > +#ifndef __PHY_LVDS_H_
> > +#define __PHY_LVDS_H_
> > +
> > +/**
> > + * struct phy_configure_opts_lvds - LVDS configuration set
> > + *
> > + * This structure is used to represent the configuration state of a
> > + * LVDS phy.
> > + */
> > +struct phy_configure_opts_lvds {
> > +	/**
> > +	 * @bits_per_lane_and_dclk_cycle:
> > +	 *
> > +	 * Number of bits per data lane and differential clock cycle.
> > +	 */
> > +	unsigned int bits_per_lane_and_dclk_cycle;
> 
> I see in patch 4/4 that you only support 7, can the value be any
> different ?

Patch 4/4 is for the Mixel combo PHY embedded in i.MX8qxp SoC.
This PHY can only do 7.

i.MX8qm SoC embeds another type of Mixel LVDS PHY which can do either 7
or 10(configurable with a register bit called 'NB').  A PHY driver for
it is yet to be upstreamed.

Regards,
Liu Ying

> 
> > +
> > +	/**
> > +	 * @differential_clk_rate:
> > +	 *
> > +	 * Clock rate, in Hertz, of the LVDS differential clock.
> > +	 */
> > +	unsigned long differential_clk_rate;
> > +
> > +	/**
> > +	 * @lanes:
> > +	 *
> > +	 * Number of active, consecutive, data lanes, starting from
> > +	 * lane 0, used for the transmissions.
> > +	 */
> > +	unsigned int lanes;
> > +
> > +	/**
> > +	 * @is_slave:
> > +	 *
> > +	 * Boolean, true if the phy is a slave which works together
> > +	 * with a master phy to support dual link transmission,
> > +	 * otherwise a regular phy or a master phy.
> > +	 */
> > +	bool is_slave;
> > +};
> > +
> > +#endif /* __PHY_LVDS_H_ */
> > diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
> > index e435bdb..d450b44 100644
> > --- a/include/linux/phy/phy.h
> > +++ b/include/linux/phy/phy.h
> > @@ -17,6 +17,7 @@
> >  #include <linux/regulator/consumer.h>
> >  
> >  #include <linux/phy/phy-dp.h>
> > +#include <linux/phy/phy-lvds.h>
> >  #include <linux/phy/phy-mipi-dphy.h>
> >  
> >  struct phy;
> > @@ -51,10 +52,13 @@ enum phy_mode {
> >   *		the MIPI_DPHY phy mode.
> >   * @dp:		Configuration set applicable for phys supporting
> >   *		the DisplayPort protocol.
> > + * @lvds:	Configuration set applicable for phys supporting
> > + *		the LVDS phy mode.
> >   */
> >  union phy_configure_opts {
> >  	struct phy_configure_opts_mipi_dphy	mipi_dphy;
> >  	struct phy_configure_opts_dp		dp;
> > +	struct phy_configure_opts_lvds		lvds;
> >  };
> >  
> >  /**