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| author | Tomi Valkeinen <tomi.valkeinen@ti.com> | 2019-05-28 11:27:37 +0300 |
|---|---|---|
| committer | Andrzej Hajda <a.hajda@samsung.com> | 2019-05-31 15:41:24 +0200 |
| commit | 0776a269d725e6ce17ae5ea033e1925be861e2f1 (patch) | |
| tree | 1900553112f363310c513b965d2531553855a502 /drivers/gpu/drm/bridge/tc358767.c | |
| parent | 31b4c8848a89be23b6706a86fc413f93115a6a1e (diff) | |
| download | talos-op-linux-0776a269d725e6ce17ae5ea033e1925be861e2f1.tar.gz talos-op-linux-0776a269d725e6ce17ae5ea033e1925be861e2f1.zip | |
drm/bridge: tc358767: use more reliable seq when finishing LT
At the end of the link training, two steps have to be taken: 1)
tc358767's LT mode is disabled by a write to DP0_SRCCTRL, and 2) Remove
LT flag in DPCD 0x102.
Toshiba's documentation tells to first write the DPCD, then modify
DP0_SRCCTRL. In my testing this often causes issues, and the link
disconnects right after those steps.
If I reverse the steps, it works every time. There's a chance that this
is DP sink specific, though, but as my testing shows this sequence to be
much more reliable, let's change it.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190528082747.3631-15-tomi.valkeinen@ti.com
Diffstat (limited to 'drivers/gpu/drm/bridge/tc358767.c')
| -rw-r--r-- | drivers/gpu/drm/bridge/tc358767.c | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c index a60a2e65e468..40f3efcade50 100644 --- a/drivers/gpu/drm/bridge/tc358767.c +++ b/drivers/gpu/drm/bridge/tc358767.c @@ -961,6 +961,18 @@ static int tc_main_link_enable(struct tc_data *tc) if (ret) goto err; + /* + * Toshiba's documentation suggests to first clear DPCD 0x102, then + * clear the training pattern bit in DP0_SRCCTRL. Testing shows + * that the link sometimes drops if those steps are done in that order, + * but if the steps are done in reverse order, the link stays up. + * + * So we do the steps differently than documented here. + */ + + /* Clear Training Pattern, set AutoCorrect Mode = 1 */ + tc_write(DP0_SRCCTRL, tc_srcctrl(tc) | DP0_SRCCTRL_AUTOCORRECT); + /* Clear DPCD 0x102 */ /* Note: Can Not use DP0_SNKLTCTRL (0x06E4) short cut */ tmp[0] = tc->link.scrambler_dis ? DP_LINK_SCRAMBLING_DISABLE : 0x00; @@ -968,9 +980,6 @@ static int tc_main_link_enable(struct tc_data *tc) if (ret < 0) goto err_dpcd_write; - /* Clear Training Pattern, set AutoCorrect Mode = 1 */ - tc_write(DP0_SRCCTRL, tc_srcctrl(tc) | DP0_SRCCTRL_AUTOCORRECT); - /* Wait */ timeout = 100; do { |
