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

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Date:   Fri, 18 May 2018 11:36:56 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     Brian Norris <briannorris@...omium.org>, hl <hl@...k-chips.com>,
        Sean Paul <seanpaul@...omium.org>, devicetree@...r.kernel.org,
        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 Fri, May 18, 2018 at 10:52:17AM +0200, Heiko Stuebner wrote:
> Am Freitag, 18. Mai 2018, 03:45:46 CEST schrieb Brian Norris:
> > 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...
> 
> I'd think so too. This is in Rockchip-specific code so it will always be
> possible to easily get the soc-type and thus phy-type, if that combination
> really changes down the road.
> 

So in the absence of a better solution, and with prior art,

Reviewed-by: Sean Paul <seanpaul@...omium.org>


We just need some eyes on the dt and phy changes in this set. Heiko, can you
help out with that?

Sean

> 
> Heiko
> 
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS