linux-kernel - Re: [PATCH drm-dp 4/4] drm/hisilicon/hibmc: add dp module in hibmc

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Message-ID: <CAA8EJpontTXUd0TzvwJZ4gCZ2i6vdB8+PqE+W3ChCuBH3WkfaA@mail.gmail.com>
Date: Mon, 21 Oct 2024 22:03:05 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: s00452708 <shiyongbang@...wei.com>
Cc: xinliang.liu@...aro.org, tiantao6@...ilicon.com, 
	maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de, 
	airlied@...il.com, daniel@...ll.ch, kong.kongxinwei@...ilicon.com, 
	liangjian010@...wei.com, chenjianmin@...wei.com, lidongming5@...wei.com, 
	libaihan@...wei.com, shenjian15@...wei.com, shaojijie@...wei.com, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-dp 4/4] drm/hisilicon/hibmc: add dp module in hibmc

On Mon, 21 Oct 2024 at 14:54, s00452708 <shiyongbang@...wei.com> wrote:
>
> Thanks, I will modify codes according to your comments, and I also
> replied some questions or reasons why I did it below.
>
> > On Mon, Sep 30, 2024 at 06:06:10PM +0800, shiyongbang wrote:
> >> From: baihan li <libaihan@...wei.com>
> >>
> >> To support DP interface displaying in hibmc driver. Add
> >> a encoder and connector for DP modual.
> >>
> >> Signed-off-by: baihan li <libaihan@...wei.com>
> >> ---
> >>   drivers/gpu/drm/hisilicon/hibmc/Makefile      |   2 +-
> >>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c    | 195 ++++++++++++++++++
> >>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c   |  17 +-
> >>   .../gpu/drm/hisilicon/hibmc/hibmc_drm_drv.h   |   5 +
> >>   4 files changed, 217 insertions(+), 2 deletions(-)
> >>   create mode 100644 drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_dp.c
> >>

[...]

> >> +
> >> +static int hibmc_dp_connector_get_modes(struct drm_connector *connector)
> >> +{
> >> +    int count;
> >> +
> >> +    count = drm_add_modes_noedid(connector, connector->dev->mode_config.max_width,
> >> +                                 connector->dev->mode_config.max_height);
> >> +    drm_set_preferred_mode(connector, 800, 600); /* default 800x600 */
> > What? Please parse EDID instead.
> > I'll add aux over i2c r/w and get edid functions in next patch.

At least please mention that it's a temporal stub which will be changed later.

> >> +
> >> +    return count;
> >> +}
> >> +

[...]

> >> @@ -116,10 +120,17 @@ static int hibmc_kms_init(struct hibmc_drm_private *priv)
> >>              return ret;
> >>      }
> >>
> >> +    /* if DP existed, init DP */
> >> +    if ((readl(priv->mmio + DP_HOST_SERDES_CTRL) &
> >> +         DP_HOST_SERDES_CTRL_MASK) == DP_HOST_SERDES_CTRL_VAL) {
> >> +            ret = hibmc_dp_init(priv);
> >> +            if (ret)
> >> +                    drm_err(dev, "failed to init dp: %d\n", ret);
> >> +    }
> >> +
> >>      ret = hibmc_vdac_init(priv);
> >>      if (ret) {
> >>              drm_err(dev, "failed to init vdac: %d\n", ret);
> >> -            return ret;
> > Why?
> > We have two display cables, if VGA cannot work, this change makes DP
> > still work.

But that has nothing to do with init errors. If initialising (aka
probing) VGA fails, then the driver init should fail. At the runtime
the VGA and DP should be independent and it should be possible to
drive just one output, that's true.

-- 
With best wishes
Dmitry