RE: [PATCH] drm/bridge: Add 200ms delay to wait FW HPD status stable

[Xin Ji]

Hi Jani Nikula, thanks for reviewing, I'll use msleep instead,  thanks!
Xin

> -----Original Message-----
> From: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Sent: Thursday, September 21, 2023 8:09 PM
> To: Xin Ji <xji@xxxxxxxxxxxxxxxx>; Andrzej Hajda <andrzej.hajda@xxxxxxxxx>;
> Neil Armstrong <neil.armstrong@xxxxxxxxxx>; Robert Foss <rfoss@xxxxxxxxxx>;
> Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>; Jonas Karlman
> <jonas@xxxxxxxxx>; Jernej Skrabec <jernej.skrabec@xxxxxxxxx>; David Airlie
> <airlied@xxxxxxxxx>; Daniel Vetter <daniel@xxxxxxxx>
> Cc: Qilin Wen <qwen@xxxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; dri-
> devel@xxxxxxxxxxxxxxxxxxxxx; hsinyi@xxxxxxxxxxxx; Bernie Liang
> <bliang@xxxxxxxxxxxxxxxx>; Xin Ji <xji@xxxxxxxxxxxxxxxx>
> Subject: Re: [PATCH] drm/bridge: Add 200ms delay to wait FW HPD status stable
> 
> On Thu, 21 Sep 2023, Xin Ji <xji@xxxxxxxxxxxxxxxx> wrote:
> > For the none-interrupt design(sink device is panel, polling HPD status
> > when chip power on), anx7625 FW has more than 200ms HPD de-bounce time
> > in FW, for the safety to get HPD status, driver better to wait 200ms
> > before HPD detection after OS resume back.
> >
> > Signed-off-by: Xin Ji <xji@xxxxxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/bridge/analogix/anx7625.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c
> > b/drivers/gpu/drm/bridge/analogix/anx7625.c
> > index 51abe42c639e..833d6d50a03d 100644
> > --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
> > +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
> > @@ -1464,6 +1464,9 @@ static int _anx7625_hpd_polling(struct
> anx7625_data *ctx,
> >  	if (ctx->pdata.intp_irq)
> >  		return 0;
> >
> > +	/* Delay 200ms for FW HPD de-bounce */
> > +	usleep_range(200000, 201000);
> 
> If you need to sleep for 200 ms, maybe use msleep instead?
OK
> 
> BR,
> Jani.
> 
> > +
> >  	ret = readx_poll_timeout(anx7625_read_hpd_status_p0,
> >  				 ctx, val,
> >  				 ((val & HPD_STATUS) || (val < 0)),
> 
> --
> Jani Nikula, Intel