Commit f0ddbb1e authored by Dave Airlie's avatar Dave Airlie
Browse files

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: default avatarDave Airlie <airlied@redhat.com>
Reviewed-by: default avatarBen Skeggs <bskeggs@nvidia.com>
Reviewed-by: default avatarTimur Tabi <ttabi@nvidia.com>
Tested-by: default avatarTimur Tabi <ttabi@nvidia.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 284ad706

drivers/gpu/drm/display/drm_dp_helper.c

+23 −16
Original line number Diff line number Diff line
@@ -2137,6 +2137,8 @@ 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;



		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
@@ -2145,6 +2147,7 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, 
			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);



			/*
@@ -2180,6 +2185,8 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, 
	}

	if (err >= 0)

		err = num;



	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.
@@ -2188,7 +2195,7 @@ static int drm_dp_i2c_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, 
		msg.buffer = NULL;

		msg.size = 0;

		(void)drm_dp_i2c_do_msg(aux, &msg);



	}

	return err;

}

include/drm/display/drm_dp_helper.h

+5 −0
Original line number Diff line number Diff line
@@ -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);