linux-kernel - Re: [PATCH v1] phy: Add DisplayPort configuration options

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Message-ID: <ca6d9a16-0cba-cde7-f60c-75305f88bf33@ti.com>
Date:   Mon, 23 Dec 2019 17:57:17 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Yuti Amonkar <yamonkar@...ence.com>,
        <linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>
CC:     <praneeth@...com>, <tomi.valkeinen@...com>, <jsarha@...com>,
        <mparab@...ence.com>, <sjakhade@...ence.com>
Subject: Re: [PATCH v1] phy: Add DisplayPort configuration options

+ Maxime

Hi,

On 23/12/19 12:24 PM, Yuti Amonkar wrote:
> Allow DisplayPort PHYs to be configured through the generic
> functions through a custom structure added to the generic union.
> The configuration structure is used for reconfiguration of
> DisplayPort PHYs during link training operation.
> 
> The parameters added here are the ones defined in the DisplayPort
> spec which include link rate, number of lanes, voltage swing
> and pre-emphasis.

Which version of display port specification?

Rest of commit log should move below the "---"


> 
> This patch was a part of [1] series earlier but we think that it needs
> to have a separate attention of the reviewers. Also as both [1] & [2] are
> dependent on this patch, our sincere request to reviewers to have a
> faster review of this patch.
> 
> [1]
> 
> https://lkml.org/lkml/2019/12/11/455
> 
> [2]
> 
> https://patchwork.kernel.org/cover/11271191/

Thanks
Kishon

> 
> Signed-off-by: Yuti Amonkar <yamonkar@...ence.com>
> ---
>   include/linux/phy/phy-dp.h | 95 ++++++++++++++++++++++++++++++++++++++++++++++
>   include/linux/phy/phy.h    |  4 ++
>   2 files changed, 99 insertions(+)
>   create mode 100644 include/linux/phy/phy-dp.h
> 
> diff --git a/include/linux/phy/phy-dp.h b/include/linux/phy/phy-dp.h
> new file mode 100644
> index 0000000..18cad23
> --- /dev/null
> +++ b/include/linux/phy/phy-dp.h
> @@ -0,0 +1,95 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2019 Cadence Design Systems Inc.
> + */
> +
> +#ifndef __PHY_DP_H_
> +#define __PHY_DP_H_
> +
> +#include <linux/types.h>
> +
> +/**
> + * struct phy_configure_opts_dp - DisplayPort PHY configuration set
> + *
> + * This structure is used to represent the configuration state of a
> + * DisplayPort phy.
> + */
> +struct phy_configure_opts_dp {
> +	/**
> +	 * @link_rate:
> +	 *
> +	 * Link Rate, in Mb/s, of the main link.
> +	 *
> +	 * Allowed values: 1620, 2160, 2430, 2700, 3240, 4320, 5400, 8100 Mb/s
> +	 */
> +	unsigned int link_rate;
> +
> +	/**
> +	 * @lanes:
> +	 *
> +	 * Number of active, consecutive, data lanes, starting from
> +	 * lane 0, used for the transmissions on main link.
> +	 *
> +	 * Allowed values: 1, 2, 4
> +	 */
> +	unsigned int lanes;
> +
> +	/**
> +	 * @voltage:
> +	 *
> +	 * Voltage swing levels, as specified by DisplayPort specification,
> +	 * to be used by particular lanes. One value per lane.
> +	 * voltage[0] is for lane 0, voltage[1] is for lane 1, etc.
> +	 *
> +	 * Maximum value: 3
> +	 */
> +	unsigned int voltage[4];
> +
> +	/**
> +	 * @pre:
> +	 *
> +	 * Pre-emphasis levels, as specified by DisplayPort specification, to be
> +	 * used by particular lanes. One value per lane.
> +	 *
> +	 * Maximum value: 3
> +	 */
> +	unsigned int pre[4];
> +
> +	/**
> +	 * @ssc:
> +	 *
> +	 * Flag indicating, whether or not to enable spread-spectrum clocking.
> +	 *
> +	 */
> +	u8 ssc : 1;
> +
> +	/**
> +	 * @set_rate:
> +	 *
> +	 * Flag indicating, whether or not reconfigure link rate and SSC to
> +	 * requested values.
> +	 *
> +	 */
> +	u8 set_rate : 1;
> +
> +	/**
> +	 * @set_lanes:
> +	 *
> +	 * Flag indicating, whether or not reconfigure lane count to
> +	 * requested value.
> +	 *
> +	 */
> +	u8 set_lanes : 1;
> +
> +	/**
> +	 * @set_voltages:
> +	 *
> +	 * Flag indicating, whether or not reconfigure voltage swing
> +	 * and pre-emphasis to requested values. Only lanes specified
> +	 * by "lanes" parameter will be affected.
> +	 *
> +	 */
> +	u8 set_voltages : 1;
> +};
> +
> +#endif /* __PHY_DP_H_ */
> diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
> index 15032f14..ba0aab5 100644
> --- a/include/linux/phy/phy.h
> +++ b/include/linux/phy/phy.h
> @@ -16,6 +16,7 @@
>   #include <linux/pm_runtime.h>
>   #include <linux/regulator/consumer.h>
>   
> +#include <linux/phy/phy-dp.h>
>   #include <linux/phy/phy-mipi-dphy.h>
>   
>   struct phy;
> @@ -46,9 +47,12 @@ enum phy_mode {
>    *
>    * @mipi_dphy:	Configuration set applicable for phys supporting
>    *		the MIPI_DPHY phy mode.
> + * @dp:		Configuration set applicable for phys supporting
> + *		the DisplayPort protocol.
>    */
>   union phy_configure_opts {
>   	struct phy_configure_opts_mipi_dphy	mipi_dphy;
> +	struct phy_configure_opts_dp		dp;
>   };
>   
>   /**
>