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 sfr@xxxxxxxxxxxxxxxx
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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