linux-kernel - Re: [PATCH] drm/bridge: Add 200ms delay to wait FW HPD status stable

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Message-ID: <20230921121305.GA19112@pendragon.ideasonboard.com>
Date:   Thu, 21 Sep 2023 15:13:05 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Xin Ji <xji@...logixsemi.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, qwen@...logixsemi.com,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        hsinyi@...omium.org, bliang@...logixsemi.com
Subject: Re: [PATCH] drm/bridge: Add 200ms delay to wait FW HPD status stable

The subject line is missing the driver name.

On Thu, Sep 21, 2023 at 03:09:10PM +0300, Jani Nikula wrote:
> On Thu, 21 Sep 2023, Xin Ji <xji@...logixsemi.com> wrote:
> > For the none-interrupt design(sink device is panel, polling HPD

s/none-interrupt/no-interrupt/ ?

s/design/design /

> > 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@...logixsemi.com>
> > ---
> >  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?

fsleep() could be a nice replacement.

> > +
> >  	ret = readx_poll_timeout(anx7625_read_hpd_status_p0,
> >  				 ctx, val,
> >  				 ((val & HPD_STATUS) || (val < 0)),

-- 
Regards,

Laurent Pinchart