On 9/12/2022 11:37 AM, Dmitry Baryshkov wrote:
On 12/09/2022 19:23, Kuogee Hsieh wrote:
Bring sink out of D3 (power down) mode into D0 (normal operation) mode
by setting DP_SET_POWER_D0 bit to DP_SET_POWER dpcd register. This
patch will retry 3 times if written to DP_SET_POWER register failed.
Could you please elaborate this change? Can the sink succeed in
reading the DP_SET_POWER, but fail writing DP_SET_POWER?
yes, there is possible since it is not only set local sink device but
also all downstream sink devices to D0 state.
Changes in v5:
-- split into two patches
Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
---
drivers/gpu/drm/msm/dp/dp_link.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/msm/dp/dp_link.c
b/drivers/gpu/drm/msm/dp/dp_link.c
index 9d5381d..4360728 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.c
+++ b/drivers/gpu/drm/msm/dp/dp_link.c
@@ -50,6 +50,7 @@ static int dp_aux_link_power_up(struct drm_dp_aux
*aux,
{
u8 value;
ssize_t len;
+ int i;
if (link->revision < 0x11)
return 0;
@@ -61,11 +62,13 @@ static int dp_aux_link_power_up(struct drm_dp_aux
*aux,
value &= ~DP_SET_POWER_MASK;
value |= DP_SET_POWER_D0;
- len = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
- if (len < 0)
- return len;
-
- usleep_range(1000, 2000);
+ /* retry for 1ms to give the sink time to wake up */
+ for (i = 0; i < 3; i++) {
+ len = drm_dp_dpcd_writeb(aux, DP_SET_POWER, value);
+ usleep_range(1000, 2000);
+ if (len == 1)
+ break;
+ }
return 0;
}
