[PATCH] drm/bridge: tc358767: fix poll timeouts

[Andrey Smirnov]

+ Chris Healy

On Mon, Dec 9, 2019 at 12:27 AM Tomi Valkeinen <tomi.valkeinen at ti.com> wrote:
>
> Link training fails with:
>
>   Link training timeout waiting for LT_LOOPDONE!
>   main link enable error: -110
>
> This is caused by too tight timeouts, which were changed recently in
> aa92213f388b ("drm/bridge: tc358767: Simplify polling in tc_link_training()").
>
> With a quick glance, the commit does not change the timeouts. However,
> the method of delaying/sleeping is different, and as the timeout in the
> previous implementation was not explicit, the new version in practice
> has much tighter timeout.
>
> The same change was made to other parts in the driver, but the link
> training timeout is the only one I have seen causing issues.
> Nevertheless, 1 us sleep is not very sane, and the timeouts look pretty
> tight, so lets fix all the timeouts.
>
> One exception was the aux busy poll, where the poll sleep was much
> longer than necessary (or optimal).
>
> I measured the times on my setup, and now the sleep times are set to
> such values that they result in multiple loops, but not too many (say,
> 5-10 loops). The timeouts were all increased to 100ms, which should be
> more than enough for all of these, but in case of bad errors, shouldn't
> stop the driver as multi-second timeouts could do.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
> Fixes: aa92213f388b ("drm/bridge: tc358767: Simplify polling in tc_link_training()")

Tested on RDU2 with TC358767/eDP panel, doesn't seem to break anything
there, so:

Tested-by: Andrey Smirnov <andrew.smirnov at gmail.com>

> ---
>  drivers/gpu/drm/bridge/tc358767.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 8a8d605021f0..0454675a44cb 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -294,7 +294,7 @@ static inline int tc_poll_timeout(struct tc_data *tc, unsigned int addr,
>
>  static int tc_aux_wait_busy(struct tc_data *tc)
>  {
> -       return tc_poll_timeout(tc, DP0_AUXSTATUS, AUX_BUSY, 0, 1000, 100000);
> +       return tc_poll_timeout(tc, DP0_AUXSTATUS, AUX_BUSY, 0, 100, 100000);
>  }
>
>  static int tc_aux_write_data(struct tc_data *tc, const void *data,
> @@ -637,7 +637,7 @@ static int tc_aux_link_setup(struct tc_data *tc)
>         if (ret)
>                 goto err;
>
> -       ret = tc_poll_timeout(tc, DP_PHY_CTRL, PHY_RDY, PHY_RDY, 1, 1000);
> +       ret = tc_poll_timeout(tc, DP_PHY_CTRL, PHY_RDY, PHY_RDY, 100, 100000);
>         if (ret == -ETIMEDOUT) {
>                 dev_err(tc->dev, "Timeout waiting for PHY to become ready");
>                 return ret;
> @@ -861,7 +861,7 @@ static int tc_wait_link_training(struct tc_data *tc)
>         int ret;
>
>         ret = tc_poll_timeout(tc, DP0_LTSTAT, LT_LOOPDONE,
> -                             LT_LOOPDONE, 1, 1000);
> +                             LT_LOOPDONE, 500, 100000);
>         if (ret) {
>                 dev_err(tc->dev, "Link training timeout waiting for LT_LOOPDONE!\n");
>                 return ret;
> @@ -934,7 +934,7 @@ static int tc_main_link_enable(struct tc_data *tc)
>         dp_phy_ctrl &= ~(DP_PHY_RST | PHY_M1_RST | PHY_M0_RST);
>         ret = regmap_write(tc->regmap, DP_PHY_CTRL, dp_phy_ctrl);
>
> -       ret = tc_poll_timeout(tc, DP_PHY_CTRL, PHY_RDY, PHY_RDY, 1, 1000);
> +       ret = tc_poll_timeout(tc, DP_PHY_CTRL, PHY_RDY, PHY_RDY, 500, 100000);
>         if (ret) {
>                 dev_err(dev, "timeout waiting for phy become ready");
>                 return ret;
> --
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