When testing with a panel that's apparently a little more persnickety about the correct power sequence (specifically Samsung ATNA33XC20), we found that the ti-sn65dsi86 was doing things just slightly wrong.
Looking closely at the ti-sn65dsi86's datasheet, the power off sequence is supposed to be: 1. Clear VSTREAM_ENABLE bit 2. Stop DSI stream from GPU. DSI lanes must be placed in LP11 state. 3. Program the ML_TX_MODE to 0x0 (OFF) 4. Program the DP_NUM_LANES register to 0x0 5. Clear the DP_PLL_EN bit. 6. Deassert the EN pin. 7. Remove power from supply pins
Since we were doing the whole sequence in the "disable", I believe that step #2 (stopping the DSI stream from the GPU) wasn't happening. We also weren't setting DP_NUM_LANES to 0.
Let's fix this.
NOTE: things are a little asymmetric now. For instance, we turn the PLL on in "enable" but now we're not turning it off until "post_disable". It would seem to make sense to move the PLL turning on to "pre_enable" to match. Unfortunately, I don't believe that's allowed. It looks as if (in the non-refclk mode which probably nobody is using) we have to wait until the MIPI clock is there before we can enable the PLL. In any case, the way it is here won't really hurt--it'll just leave the PLL on a little longer.
Fixes: a095f15c00e2 ("drm/bridge: add support for sn65dsi86 bridge driver") Signed-off-by: Douglas Anderson dianders@chromium.org Acked-by: Robert Foss robert.foss@linaro.org Reviewed-by: Sean Paul seanpaul@chromium.org ---
(no changes since v1)
drivers/gpu/drm/bridge/ti-sn65dsi86.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index 9bf889302bcc..5e932070a1c3 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -766,10 +766,6 @@ static void ti_sn_bridge_disable(struct drm_bridge *bridge)
/* disable video stream */ regmap_update_bits(pdata->regmap, SN_ENH_FRAME_REG, VSTREAM_ENABLE, 0); - /* semi auto link training mode OFF */ - regmap_write(pdata->regmap, SN_ML_TX_MODE_REG, 0); - /* disable DP PLL */ - regmap_write(pdata->regmap, SN_PLL_ENABLE_REG, 0); }
static void ti_sn_bridge_set_dsi_rate(struct ti_sn65dsi86 *pdata) @@ -1106,6 +1102,13 @@ static void ti_sn_bridge_post_disable(struct drm_bridge *bridge) { struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
+ /* semi auto link training mode OFF */ + regmap_write(pdata->regmap, SN_ML_TX_MODE_REG, 0); + /* Num lanes to 0 as per power sequencing in data sheet */ + regmap_update_bits(pdata->regmap, SN_SSC_CONFIG_REG, DP_NUM_LANES_MASK, 0); + /* disable DP PLL */ + regmap_write(pdata->regmap, SN_PLL_ENABLE_REG, 0); + if (!pdata->refclk) ti_sn65dsi86_disable_comms(pdata);