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Subject: Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in
 tc_link_training()
From:   Tomi Valkeinen <tomi.valkeinen@ti.com>
To:     Andrey Smirnov <andrew.smirnov@gmail.com>,
        <dri-devel@lists.freedesktop.org>
CC:     Andrzej Hajda <a.hajda@samsung.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrey Gusakov <andrey.gusakov@cogentembedded.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Cory Tusar <cory.tusar@zii.aero>,
        Chris Healy <cphealy@gmail.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        <linux-kernel@vger.kernel.org>, Jyri Sarha <jsarha@ti.com>
References: <20190619052716.16831-1-andrew.smirnov@gmail.com>
 <20190619052716.16831-4-andrew.smirnov@gmail.com>
 <0d84fa72-bc96-9b88-cd89-c04327109e0e@ti.com>
Message-ID: <bdf4df0a-06d7-2ccb-9e8a-0c0ad55871ec@ti.com>
Date:   Wed, 4 Dec 2019 21:13:54 +0200
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On 04/12/2019 20:27, Tomi Valkeinen wrote:
> Hi Andrey,
> 
> On 19/06/2019 08:27, Andrey Smirnov wrote:
> 
>> @@ -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);
> 
> This seems to break DP at least with some monitors for me. I think it's just a timeout problem, as 
> increasing the values helps.
> 
> Using ktime, I can see that during link training, the first call takes ~2ms, the second ~7ms. I 
> think this worked before, as udelay(1) takes much longer than 1 us.

Also the timeout in tc_aux_link_setup takes ~500us for me, and max is 1000us. So it works, but I 
think it's a bit tight.

  Tomi

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