Re: [PATCH drm-dp 05/10] drm/hisilicon/hibmc: fix rare monitors cannot display problem

[Yongbang Shi]

> On Fri, May 30, 2025 at 05:54:27PM +0800, Yongbang Shi wrote:
> > From: Baihan Li <libaihan@xxxxxxxxxx>
> >
> > DP Link training successful at 8.1Gbps with some monitors' max link rate
> > are 2.7Gbps. So change the default 8.1Gbps link rate to the rate that reads
> > from devices' capabilities.
> I've hard time understanding this message.

Sorry for misunderstanding. The problem is that dp link training success at 8.1Gbps, however,

the sink 's maximum supported rate is less than 8.1G.


> > Fixes: f9698f802e50 ("drm/hisilicon/hibmc: Restructuring the header dp_reg.h")
> No, the tag is incorrect. Mentioned commit is not related.

Ok.


> > Signed-off-by: Baihan Li <libaihan@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/hisilicon/hibmc/dp/dp_comm.h  |  4 ++-
> >   drivers/gpu/drm/hisilicon/hibmc/dp/dp_hw.c    |  6 +---
> >   drivers/gpu/drm/hisilicon/hibmc/dp/dp_link.c  | 33 +++++++++++++------
> >   .../gpu/drm/hisilicon/hibmc/dp/dp_serdes.c    | 12 -------
> >   4 files changed, 27 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c
> > index 676059d4c1e6..8191233aa965 100644
> > --- a/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c
> > +++ b/drivers/gpu/drm/hisilicon/hibmc/dp/dp_serdes.c
> > @@ -57,15 +57,3 @@ int hibmc_dp_serdes_rate_switch(u8 rate, struct hibmc_dp_dev *dp)
> >   
> >   	return 0;
> >   }
> > -
> > -int hibmc_dp_serdes_init(struct hibmc_dp_dev *dp)
> > -{
> > -	dp->serdes_base = dp->base + HIBMC_DP_HOST_OFFSET;
> > -
> > -	writel(FIELD_PREP(HIBMC_DP_PMA_TXDEEMPH, DP_SERDES_VOL0_PRE0),
> > -	       dp->serdes_base + HIBMC_DP_PMA_LANE0_OFFSET);
> > -	writel(FIELD_PREP(HIBMC_DP_PMA_TXDEEMPH, DP_SERDES_VOL0_PRE0),
> > -	       dp->serdes_base + HIBMC_DP_PMA_LANE1_OFFSET);
> Where did these two writes go?

It's the same as the cfg in hibmc_dp_serdes_set_tx_cfg(), and this function will be called certainly.


> > -
> > -	return hibmc_dp_serdes_rate_switch(DP_SERDES_BW_8_1, dp);
> > -}
> > --
> > 2.33.0