linux-kernel - Re: [PATCH v5 4/4] drm/rockchip: support dp training outside dp firmware

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Date:   Thu, 17 May 2018 18:45:46 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     hl <hl@...k-chips.com>
Cc:     Sean Paul <seanpaul@...omium.org>, devicetree@...r.kernel.org,
        Heiko Stuebner <heiko@...ech.de>,
        David Airlie <airlied@...ux.ie>,
        Enric Balletbo Serra <eballetbo@...il.com>,
        Doug Anderson <dianders@...omium.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Rob Herring <robh+dt@...nel.org>,
        dri-devel@...ts.freedesktop.org, Chris Zhong <zyw@...k-chips.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        linux-arm-kernel@...ts.infradead.org,
        Kishon Vijay Abraham I <kishon@...com>
Subject: Re: [PATCH v5 4/4] drm/rockchip: support dp training outside dp firmware

On Thu, May 17, 2018 at 6:41 PM, hl <hl@...k-chips.com> wrote:
> On Thursday, May 17, 2018 09:51 PM, Sean Paul wrote:
>> On Thu, May 17, 2018 at 05:18:00PM +0800, Lin Huang wrote:
>>> DP firmware uses fixed phy config values to do training, but some
>>> boards need to adjust these values to fit for their unique hardware
>>> design. So get phy config values from dts and use software link training
>>> instead of relying on firmware, if software training fail, keep firmware
>>> training as a fallback if sw training fails.
>>>
>>> Signed-off-by: Chris Zhong <zyw@...k-chips.com>
>>> Signed-off-by: Lin Huang <hl@...k-chips.com>
>>> ---
>>> Changes in v2:
>>> - update patch following Enric suggest
>>> Changes in v3:
>>> - use variable fw_training instead sw_training_success
>>> - base on DP SPCE, if training fail use lower link rate to retry training
>>> Changes in v4:
>>> - improve cdn_dp_get_lower_link_rate() and cdn_dp_software_train_link() follow Sean suggest
>>> Changes in v5:
>>> - fix some whitespcae issue
>>>
>>>   drivers/gpu/drm/rockchip/Makefile               |   3 +-
>>>   drivers/gpu/drm/rockchip/cdn-dp-core.c          |  24 +-
>>>   drivers/gpu/drm/rockchip/cdn-dp-core.h          |   2 +
>>>   drivers/gpu/drm/rockchip/cdn-dp-link-training.c | 420 ++++++++++++++++++++++++
>>>   drivers/gpu/drm/rockchip/cdn-dp-reg.c           |  31 +-
>>>   drivers/gpu/drm/rockchip/cdn-dp-reg.h           |  38 ++-
>>>   6 files changed, 505 insertions(+), 13 deletions(-)
>>>   create mode 100644 drivers/gpu/drm/rockchip/cdn-dp-link-training.c
>>>
...
>>> diff --git a/drivers/gpu/drm/rockchip/cdn-dp-link-training.c b/drivers/gpu/drm/rockchip/cdn-dp-link-training.c
>>> new file mode 100644
>>> index 0000000..73c3290
>>> --- /dev/null
>>> +++ b/drivers/gpu/drm/rockchip/cdn-dp-link-training.c
>>> @@ -0,0 +1,420 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright (C) Fuzhou Rockchip Electronics Co.Ltd
>>> + * Author: Chris Zhong <zyw@...k-chips.com>
>>> + */
>>> +
>>> +#include <linux/device.h>
>>> +#include <linux/delay.h>
>>> +#include <linux/phy/phy.h>
>>> +#include <soc/rockchip/rockchip_phy_typec.h>
>>> +
>>> +#include "cdn-dp-core.h"
>>> +#include "cdn-dp-reg.h"
>>> +
>>> +static void cdn_dp_set_signal_levels(struct cdn_dp_device *dp)
>>> +{
>>> +       struct cdn_dp_port *port = dp->port[dp->active_port];
>>> +       struct rockchip_typec_phy *tcphy = phy_get_drvdata(port->phy);
>>
>> You ignored Brian's comment on the previous patch:
>>    This is still antithetical to the PHY framework; you're assuming that
>>    this is a particular type of PHY here.
>>
>> FWIW, the mediatek drm driver also assumes a certain PHY type. A quick grep of
>> drivers/ shows that the only other non-phy/ driver using this function
>> (pinctrl-tegra-xusb.c) also casts it.
>>
>> Sean
>
> Thanks Sean, except phy framework have new API to handle it, i have not
> idea how to do it in a better way.

Well, if Mediatek can do it for their MIPI and HDMI, then maybe we just do it...

Brian