From f0ddbb1eed1898286d2bd99fd6ab64ca9700d267 Mon Sep 17 00:00:00 2001 From: Dave Airlie Date: Tue, 4 Mar 2025 01:56:03 +1000 Subject: [PATCH 3704/5403] drm/dp: add option to disable zero sized address only transactions. Some older NVIDIA and some newer NVIDIA hardware/firmware seems to have issues with address only transactions (firmware rejects them). Add an option to the core drm dp to avoid address only transactions, This just puts the MOT flag removal on the last message of the transfer and avoids the start of transfer transaction. This with the flag set in nouveau, allows eDP probing on GB203 device. Signed-off-by: Dave Airlie Reviewed-by: Ben Skeggs Reviewed-by: Timur Tabi Tested-by: Timur Tabi Signed-off-by: Dave Airlie --- drivers/gpu/drm/display/drm_dp_helper.c | 39 +++++++++++++++---------- include/drm/display/drm_dp_helper.h | 5 ++++ 2 files changed, 28 insertions(+), 16 deletions(-) diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index 56c7e3318f01..f2a6559a2710 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -2137,14 +2137,17 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, for (i = 0; i < num; i++) { msg.address = msgs[i].addr; - drm_dp_i2c_msg_set_request(&msg, &msgs[i]); - /* Send a bare address packet to start the transaction. - * Zero sized messages specify an address only (bare - * address) transaction. - */ - msg.buffer = NULL; - msg.size = 0; - err = drm_dp_i2c_do_msg(aux, &msg); + + if (!aux->no_zero_sized) { + drm_dp_i2c_msg_set_request(&msg, &msgs[i]); + /* Send a bare address packet to start the transaction. + * Zero sized messages specify an address only (bare + * address) transaction. + */ + msg.buffer = NULL; + msg.size = 0; + err = drm_dp_i2c_do_msg(aux, &msg); + } /* * Reset msg.request in case in case it got @@ -2163,6 +2166,8 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, msg.buffer = msgs[i].buf + j; msg.size = min(transfer_size, msgs[i].len - j); + if (j + msg.size == msgs[i].len && aux->no_zero_sized) + msg.request &= ~DP_AUX_I2C_MOT; err = drm_dp_i2c_drain_msg(aux, &msg); /* @@ -2180,15 +2185,17 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, } if (err >= 0) err = num; - /* Send a bare address packet to close out the transaction. - * Zero sized messages specify an address only (bare - * address) transaction. - */ - msg.request &= ~DP_AUX_I2C_MOT; - msg.buffer = NULL; - msg.size = 0; - (void)drm_dp_i2c_do_msg(aux, &msg); + if (!aux->no_zero_sized) { + /* Send a bare address packet to close out the transaction. + * Zero sized messages specify an address only (bare + * address) transaction. + */ + msg.request &= ~DP_AUX_I2C_MOT; + msg.buffer = NULL; + msg.size = 0; + (void)drm_dp_i2c_do_msg(aux, &msg); + } return err; } diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h index 7b19192c7031..e4ca35143ff9 100644 --- a/include/drm/display/drm_dp_helper.h +++ b/include/drm/display/drm_dp_helper.h @@ -518,6 +518,11 @@ struct drm_dp_aux { * @powered_down: If true then the remote endpoint is powered down. */ bool powered_down; + + /** + * @no_zero_sized: If the hw can't use zero sized transfers (NVIDIA) + */ + bool no_zero_sized; }; int drm_dp_dpcd_probe(struct drm_dp_aux *aux, unsigned int offset); -- 2.54.0