Subject: linux-next: manual merge of the drm-misc tree with Linus' tree

From: Stephen Rothwell <[email-masked]>
Date: Sat, 12 Sep 2015 13:15:29 +1000

Hi all,

Today's linux-next merge of the drm-misc tree got a conflict in:

  drivers/gpu/drm/drm_dp_helper.c

between commits:

  79a2b161c12a ("drm/dp: Define AUX_RETRY_INTERVAL as 500 us")
  4efa83c8c786 ("drm/dp: Adjust i2c-over-aux retry count based on message size and i2c bus speed")
  f36203be608a ("drm/dp: Add dp_aux_i2c_speed_khz module param to set the assume i2c bus speed")

from Linus' tree and commit:

  68ec2a2a2481 ("drm/dp: Use I2C_WRITE_STATUS_UPDATE to drain partial I2C_WRITE requests")

from the drm-misc tree.

I fixed it up (see below) and can carry the fix as necessary (no action
is required).

-- 
Cheers,
Stephen Rothwell                    [email-masked]

diff --cc drivers/gpu/drm/drm_dp_helper.c
index 291734e87fca,5a55d905b8ee..000000000000
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@@ -424,90 -422,19 +424,103 @@@ static u32 drm_dp_i2c_functionality(str
  	       I2C_FUNC_10BIT_ADDR;
  }
  
 +#define AUX_PRECHARGE_LEN 10 /* 10 to 16 */
 +#define AUX_SYNC_LEN (16 + 4) /* preamble + AUX_SYNC_END */
 +#define AUX_STOP_LEN 4
 +#define AUX_CMD_LEN 4
 +#define AUX_ADDRESS_LEN 20
 +#define AUX_REPLY_PAD_LEN 4
 +#define AUX_LENGTH_LEN 8
 +
 +/*
 + * Calculate the duration of the AUX request/reply in usec. Gives the
 + * "best" case estimate, ie. successful while as short as possible.
 + */
 +static int drm_dp_aux_req_duration(const struct drm_dp_aux_msg *msg)
 +{
 +	int len = AUX_PRECHARGE_LEN + AUX_SYNC_LEN + AUX_STOP_LEN +
 +		AUX_CMD_LEN + AUX_ADDRESS_LEN + AUX_LENGTH_LEN;
 +
 +	if ((msg->request & DP_AUX_I2C_READ) == 0)
 +		len += msg->size * 8;
 +
 +	return len;
 +}
 +
 +static int drm_dp_aux_reply_duration(const struct drm_dp_aux_msg *msg)
 +{
 +	int len = AUX_PRECHARGE_LEN + AUX_SYNC_LEN + AUX_STOP_LEN +
 +		AUX_CMD_LEN + AUX_REPLY_PAD_LEN;
 +
 +	/*
 +	 * For read we expect what was asked. For writes there will
 +	 * be 0 or 1 data bytes. Assume 0 for the "best" case.
 +	 */
 +	if (msg->request & DP_AUX_I2C_READ)
 +		len += msg->size * 8;
 +
 +	return len;
 +}
 +
 +#define I2C_START_LEN 1
 +#define I2C_STOP_LEN 1
 +#define I2C_ADDR_LEN 9 /* ADDRESS + R/W + ACK/NACK */
 +#define I2C_DATA_LEN 9 /* DATA + ACK/NACK */
 +
 +/*
 + * Calculate the length of the i2c transfer in usec, assuming
 + * the i2c bus speed is as specified. Gives the the "worst"
 + * case estimate, ie. successful while as long as possible.
 + * Doesn't account the the "MOT" bit, and instead assumes each
 + * message includes a START, ADDRESS and STOP. Neither does it
 + * account for additional random variables such as clock stretching.
 + */
 +static int drm_dp_i2c_msg_duration(const struct drm_dp_aux_msg *msg,
 +				   int i2c_speed_khz)
 +{
 +	/* AUX bitrate is 1MHz, i2c bitrate as specified */
 +	return DIV_ROUND_UP((I2C_START_LEN + I2C_ADDR_LEN +
 +			     msg->size * I2C_DATA_LEN +
 +			     I2C_STOP_LEN) * 1000, i2c_speed_khz);
 +}
 +
 +/*
 + * Deterine how many retries should be attempted to successfully transfer
 + * the specified message, based on the estimated durations of the
 + * i2c and AUX transfers.
 + */
 +static int drm_dp_i2c_retry_count(const struct drm_dp_aux_msg *msg,
 +			      int i2c_speed_khz)
 +{
 +	int aux_time_us = drm_dp_aux_req_duration(msg) +
 +		drm_dp_aux_reply_duration(msg);
 +	int i2c_time_us = drm_dp_i2c_msg_duration(msg, i2c_speed_khz);
 +
 +	return DIV_ROUND_UP(i2c_time_us, aux_time_us + AUX_RETRY_INTERVAL);
 +}
 +
 +/*
 + * FIXME currently assumes 10 kHz as some real world devices seem
 + * to require it. We should query/set the speed via DPCD if supported.
 + */
 +static int dp_aux_i2c_speed_khz __read_mostly = 10;
 +module_param_unsafe(dp_aux_i2c_speed_khz, int, 0644);
 +MODULE_PARM_DESC(dp_aux_i2c_speed_khz,
 +		 "Assumed speed of the i2c bus in kHz, (1-400, default 10)");
 +
+ static void drm_dp_i2c_msg_write_status_update(struct drm_dp_aux_msg *msg)
+ {
+ 	/*
+ 	 * In case of i2c defer or short i2c ack reply to a write,
+ 	 * we need to switch to WRITE_STATUS_UPDATE to drain the
+ 	 * rest of the message
+ 	 */
+ 	if ((msg->request & ~DP_AUX_I2C_MOT) == DP_AUX_I2C_WRITE) {
+ 		msg->request &= DP_AUX_I2C_MOT;
+ 		msg->request |= DP_AUX_I2C_WRITE_STATUS_UPDATE;
+ 	}
+ }
+ 
  /*
   * Transfer a single I2C-over-AUX message and handle various error conditions,
   * retrying the transaction as appropriate.  It is assumed that the
@@@ -595,7 -521,8 +610,8 @@@ static int drm_dp_i2c_do_msg(struct drm
  			aux->i2c_defer_count++;
  			if (defer_i2c < 7)
  				defer_i2c++;
 -			usleep_range(400, 500);
 +			usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
+ 			drm_dp_i2c_msg_write_status_update(msg);
  			continue;
  
  		default:
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