Quoting Doug Anderson (2020-10-29 09:22:55)
Hi,
On Wed, Oct 28, 2020 at 6:12 PM Stephen Boyd swboyd@chromium.org wrote:
We should be setting the drm_dp_aux_msg::reply field if a NACK or a SHORT reply happens.
I don't think you update the "reply" field for SHORT, right? You just return a different size?
Correct.
diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c index 6b6e98ca2881..19737bc01b8f 100644 --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c @@ -909,10 +910,32 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux, ret = regmap_read(pdata->regmap, SN_AUX_CMD_STATUS_REG, &val); if (ret) return ret;
else if ((val & AUX_IRQ_STATUS_NAT_I2C_FAIL)|| (val & AUX_IRQ_STATUS_AUX_RPLY_TOUT)|| (val & AUX_IRQ_STATUS_AUX_SHORT))return -ENXIO;
if (val & AUX_IRQ_STATUS_AUX_RPLY_TOUT) {/** The hardware tried the message seven times per the DP spec* but it hit a timeout. We ignore defers here because they're* handled in hardware.*/return -ETIMEDOUT;}if (val & AUX_IRQ_STATUS_AUX_SHORT) {ret = regmap_read(pdata->regmap, SN_AUX_LENGTH_REG, &len);if (ret)return ret;IIUC, your digging through the code showed that in order to fully handle the "SHORT" case you also needed to add support for "DP_AUX_I2C_WRITE_STATUS_UPDATE", right?
Oh yeah. If a short reply happens and it is aux over i2c then drm_dp_i2c_msg_write_status_update() is called and DP_AUX_I2C_WRITE_STATUS_UPDATE is set and then we try a transfer again. We need to handle that type of request in this ti_sn_aux_transfer() function.
Even without handling "DP_AUX_I2C_WRITE_STATUS_UPDATE" though, this patch seems to be an improvement and I'd support landing it.
Oh, I guess one other thing: I think this is all from code inspection, right? You didn't manage to reproduce anything that would tickle one of these code paths? Might be worth mentioning, even if "after the cut"?
Yes, just code inspection. I can add that detail to the commit text.