linux-kernel - Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <bdf4df0a-06d7-2ccb-9e8a-0c0ad55871ec@ti.com>
Date:   Wed, 4 Dec 2019 21:13:54 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>,
        <dri-devel@...ts.freedesktop.org>
CC:     Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.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>, Jyri Sarha <jsarha@...com>
Subject: Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in
 tc_link_training()

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

-- 
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki