linux-kernel - Re: [PATCH v3 03/15] drm/bridge: tc358767: Simplify polling in tc_link

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Date:   Thu, 6 Jun 2019 10:08:02 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        dri-devel@...ts.freedesktop.org
Cc:     Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Andrey Gusakov <andrey.gusakov@...entembedded.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Cory Tusar <cory.tusar@....aero>,
        Chris Healy <cphealy@...il.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/15] drm/bridge: tc358767: Simplify polling in
 tc_link_training()

On 05.06.2019 09:04, Andrey Smirnov wrote:
> Replace explicit polling in tc_link_training() with equivalent call to
> tc_poll_timeout() for simplicity. No functional change intended (not
> including slightly altered debug output).
>
> Signed-off-by: Andrey Smirnov <andrew.smirnov@...il.com>
> Cc: Archit Taneja <architt@...eaurora.org>
> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@...com>
> Cc: Andrey Gusakov <andrey.gusakov@...entembedded.com>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> Cc: Cory Tusar <cory.tusar@....aero>
> Cc: Chris Healy <cphealy@...il.com>
> Cc: Lucas Stach <l.stach@...gutronix.de>
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 5e1e73a91696..115cffc55a96 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -748,22 +748,19 @@ static int tc_set_video_mode(struct tc_data *tc,
>  
>  static int tc_wait_link_training(struct tc_data *tc)
>  {
> -	u32 timeout = 1000;
>  	u32 value;
>  	int ret;
>  
> -	do {
> -		udelay(1);
> -		tc_read(DP0_LTSTAT, &value);
> -	} while ((!(value & LT_LOOPDONE)) && (--timeout));
> -
> -	if (timeout == 0) {
> +	ret = tc_poll_timeout(tc, DP0_LTSTAT, LT_LOOPDONE,
> +			      LT_LOOPDONE, 1, 1000);
> +	if (ret) {
>  		dev_err(tc->dev, "Link training timeout waiting for LT_LOOPDONE!\n");
> -		return -ETIMEDOUT;
> +		return ret;
>  	}


Inconsistent coding, in previous patch you check (ret == -ETIMEDOUT) but
not here. To simplify the code you can assume that tc_poll_timeout < 0,
means timeout, in such case please adjust previous patch.


Beside this:

Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>

 --
Regards
Andrzej


>  
> -	return (value >> 8) & 0x7;
> +	tc_read(DP0_LTSTAT, &value);
>  
> +	return (value >> 8) & 0x7;
>  err:
>  	return ret;
>  }