Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link_training()
On Wed, Dec 4, 2019 at 10:27 AM 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, );
> > - } 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.
>
> We have 1000us limit in a few other places too, which I don't see causing
> issues, but might need
> increasing too.
>
> Also, 1us sleep_us may be a bit too small to be sane. If the loops take
> milliseconds, probably 100us
> or even more would make sense.
>
> This didn't cause any issues with your display?
>
Hmm, not that I know of. Your reasoning makes sense, though. If
increasing the timeout helps, I am all for it. And, yeah, I agree,
this is probably not the only place that could use an increased
timeout.
Thanks,
Andrey Smirnov
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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, );
- } 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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Re: [PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link_training()
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, );
- } 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.
We have 1000us limit in a few other places too, which I don't see causing issues, but might need
increasing too.
Also, 1us sleep_us may be a bit too small to be sane. If the loops take milliseconds, probably 100us
or even more would make sense.
This didn't cause any issues with your display?
Tomi
--
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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[PATCH v6 03/15] drm/bridge: tc358767: Simplify polling in tc_link_training()
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
Reviewed-by: Andrzej Hajda
Cc: Andrzej Hajda
Cc: Laurent Pinchart
Cc: Tomi Valkeinen
Cc: Andrey Gusakov
Cc: Philipp Zabel
Cc: Cory Tusar
Cc: Chris Healy
Cc: Lucas Stach
Cc: dri-devel@lists.freedesktop.org
Cc: linux-ker...@vger.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 f463ef6d4271..31f5045e7e42 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, );
- } 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;
}
- return (value >> 8) & 0x7;
+ tc_read(DP0_LTSTAT, );
+ return (value >> 8) & 0x7;
err:
return ret;
}
--
2.21.0
