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

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Date:   Fri, 22 Sep 2023 07:00:51 +0000
From:   Xin Ji <xji@...logixsemi.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
CC:     Qilin Wen <qwen@...logixsemi.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "hsinyi@...omium.org" <hsinyi@...omium.org>,
        Bernie Liang <bliang@...logixsemi.com>
Subject: RE: [PATCH] drm/bridge: Add 200ms delay to wait FW HPD status stable

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

> -----Original Message-----
> From: Jani Nikula <jani.nikula@...ux.intel.com>
> Sent: Thursday, September 21, 2023 8:09 PM
> To: Xin Ji <xji@...logixsemi.com>; Andrzej Hajda <andrzej.hajda@...el.com>;
> Neil Armstrong <neil.armstrong@...aro.org>; Robert Foss <rfoss@...nel.org>;
> Laurent Pinchart <Laurent.pinchart@...asonboard.com>; Jonas Karlman
> <jonas@...boo.se>; Jernej Skrabec <jernej.skrabec@...il.com>; David Airlie
> <airlied@...il.com>; Daniel Vetter <daniel@...ll.ch>
> Cc: Qilin Wen <qwen@...logixsemi.com>; linux-kernel@...r.kernel.org; dri-
> devel@...ts.freedesktop.org; hsinyi@...omium.org; Bernie Liang
> <bliang@...logixsemi.com>; Xin Ji <xji@...logixsemi.com>
> Subject: Re: [PATCH] drm/bridge: Add 200ms delay to wait FW HPD status stable
> 
> On Thu, 21 Sep 2023, Xin Ji <xji@...logixsemi.com> 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@...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?
OK
> 
> BR,
> Jani.
> 
> > +
> >  	ret = readx_poll_timeout(anx7625_read_hpd_status_p0,
> >  				 ctx, val,
> >  				 ((val & HPD_STATUS) || (val < 0)),
> 
> --
> Jani Nikula, Intel