On Fri, Jul 13, 2018 at 10:32:15AM -0700, Nathan Ciobanu wrote:
> Limit the link training clock recovery loop to 10 failed attempts at
> LANEx_CR_DONE per DP 1.4 spec.
Where exactly in the spec?
> Some USB-C MST hubs cause us to get
> stuck in this loop on hot-plugging indefinitely as
> drm_dp_clock_recovery_ok() never returns true and none of the
> other conditions occur.
Although it seems really bad situation that we need to avoid...
>
> Signed-off-by: Nathan Ciobanu <nathan.d.ciobanu@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp_link_training.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 4da6e33c7fa1..66c1a70343ba 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -129,7 +129,7 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
> intel_dp_link_training_clock_recovery(struct intel_dp *intel_dp)
> {
> uint8_t voltage;
> - int voltage_tries, max_vswing_tries;
> + int voltage_tries, max_vswing_tries, cr_tries;
> uint8_t link_config[2];
> uint8_t link_bw, rate_select;
>
> @@ -172,6 +172,7 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
>
> voltage_tries = 1;
> max_vswing_tries = 0;
> + cr_tries = 0;
> for (;;) {
> uint8_t link_status[DP_LINK_STATUS_SIZE];
>
> @@ -215,6 +216,11 @@ static bool intel_dp_link_max_vswing_reached(struct intel_dp *intel_dp)
> if (intel_dp_link_max_vswing_reached(intel_dp))
> ++max_vswing_tries;
>
> + if (cr_tries == 9) {
> + DRM_ERROR("Failed clock recovery 10 times, giving up!\n");
> + return false;
> + }
> + ++cr_tries;
If I understood correctly this is a global thing for the for(;;) right?
Shouldn't we make then like a:
- for(;;)
+ for(cr_tries = 0; cr_tries < 10; cr_tries++)
{
}
+ DRM_ERROR("Failed clock recovery 10 times, giving up!\n");
+ return false;
}
Thanks,
Rodrigo.
> }
> }
>
> --
> 1.9.1
>
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