video: exynos_dp: adjust voltage swing and pre-emphasis during Link Training

This patch adds adjustement for voltage swing and pre-emphasis during
Link Training procedure. According to the DP specification, unless all
the LANEx_CR_DONE bits are set, the transmitter must read
the ADJUST_REQUEST_LANEx_x, increase the voltage swing according to
the request, and update the TRAINING_LANEx_SET bytes to match the new
voltage swing setting.

Refer to the DP specification v1.1a, Section 3.5.1.3 Link Training.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

diff --git a/drivers/video/exynos/exynos_dp_core.c b/drivers/video/exynos/exynos_dp_core.c
index c6c016a..9c0140f 100644 (file)
--- a/drivers/video/exynos/exynos_dp_core.c
+++ b/drivers/video/exynos/exynos_dp_core.c
@@ -260,7 +260,7 @@ static void exynos_dp_set_lane_lane_pre_emphasis(struct exynos_dp_device *dp,
 
 static void exynos_dp_link_start(struct exynos_dp_device *dp)
 {
-       u8 buf[5];
+       u8 buf[4];
        int lane;
        int lane_count;
 
@@ -295,10 +295,10 @@ static void exynos_dp_link_start(struct exynos_dp_device *dp)
        exynos_dp_set_training_pattern(dp, TRAINING_PTN1);
 
        /* Set RX training pattern */
-       buf[0] = DPCD_SCRAMBLING_DISABLED |
-                DPCD_TRAINING_PATTERN_1;
        exynos_dp_write_byte_to_dpcd(dp,
-               DPCD_ADDR_TRAINING_PATTERN_SET, buf[0]);
+               DPCD_ADDR_TRAINING_PATTERN_SET,
+               DPCD_SCRAMBLING_DISABLED |
+               DPCD_TRAINING_PATTERN_1);
 
        for (lane = 0; lane < lane_count; lane++)
                buf[lane] = DPCD_PRE_EMPHASIS_PATTERN2_LEVEL0 |
@@ -308,7 +308,7 @@ static void exynos_dp_link_start(struct exynos_dp_device *dp)
                lane_count, buf);
 }
 
-static unsigned char exynos_dp_get_lane_status(u8 link_status[6], int lane)
+static unsigned char exynos_dp_get_lane_status(u8 link_status[2], int lane)
 {
        int shift = (lane & 1) * 4;
        u8 link_value = link_status[lane>>1];
@@ -316,7 +316,7 @@ static unsigned char exynos_dp_get_lane_status(u8 link_status[6], int lane)
        return (link_value >> shift) & 0xf;
 }
 
-static int exynos_dp_clock_recovery_ok(u8 link_status[6], int lane_count)
+static int exynos_dp_clock_recovery_ok(u8 link_status[2], int lane_count)
 {
        int lane;
        u8 lane_status;
@@ -329,22 +329,23 @@ static int exynos_dp_clock_recovery_ok(u8 link_status[6], int lane_count)
        return 0;
 }
 
-static int exynos_dp_channel_eq_ok(u8 link_status[6], int lane_count)
+static int exynos_dp_channel_eq_ok(u8 link_align[3], int lane_count)
 {
        int lane;
        u8 lane_align;
        u8 lane_status;
 
-       lane_align = link_status[2];
+       lane_align = link_align[2];
        if ((lane_align & DPCD_INTERLANE_ALIGN_DONE) == 0)
                return -EINVAL;
 
        for (lane = 0; lane < lane_count; lane++) {
-               lane_status = exynos_dp_get_lane_status(link_status, lane);
+               lane_status = exynos_dp_get_lane_status(link_align, lane);
                lane_status &= DPCD_CHANNEL_EQ_BITS;
                if (lane_status != DPCD_CHANNEL_EQ_BITS)
                        return -EINVAL;
        }
+
        return 0;
 }
 
@@ -417,69 +418,17 @@ static unsigned int exynos_dp_get_lane_link_training(
 
 static void exynos_dp_reduce_link_rate(struct exynos_dp_device *dp)
 {
-       if (dp->link_train.link_rate == LINK_RATE_2_70GBPS) {
-               /* set to reduced bit rate */
-               dp->link_train.link_rate = LINK_RATE_1_62GBPS;
-               dev_err(dp->dev, "set to bandwidth %.2x\n",
-                       dp->link_train.link_rate);
-               dp->link_train.lt_state = START;
-       } else {
-               exynos_dp_training_pattern_dis(dp);
-               /* set enhanced mode if available */
-               exynos_dp_set_enhanced_mode(dp);
-               dp->link_train.lt_state = FAILED;
-       }
-}
-
-static void exynos_dp_get_adjust_train(struct exynos_dp_device *dp,
-                               u8 adjust_request[2])
-{
-       int lane;
-       int lane_count;
-       u8 voltage_swing;
-       u8 pre_emphasis;
-       u8 training_lane;
+       exynos_dp_training_pattern_dis(dp);
+       exynos_dp_set_enhanced_mode(dp);
 
-       lane_count = dp->link_train.lane_count;
-       for (lane = 0; lane < lane_count; lane++) {
-               voltage_swing = exynos_dp_get_adjust_request_voltage(
-                                               adjust_request, lane);
-               pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
-                                               adjust_request, lane);
-               training_lane = DPCD_VOLTAGE_SWING_SET(voltage_swing) |
-                               DPCD_PRE_EMPHASIS_SET(pre_emphasis);
-
-               if (voltage_swing == VOLTAGE_LEVEL_3 ||
-                  pre_emphasis == PRE_EMPHASIS_LEVEL_3) {
-                       training_lane |= DPCD_MAX_SWING_REACHED;
-                       training_lane |= DPCD_MAX_PRE_EMPHASIS_REACHED;
-               }
-               dp->link_train.training_lane[lane] = training_lane;
-       }
-}
-
-static int exynos_dp_check_max_cr_loop(struct exynos_dp_device *dp,
-                                       u8 voltage_swing)
-{
-       int lane;
-       int lane_count;
-
-       lane_count = dp->link_train.lane_count;
-       for (lane = 0; lane < lane_count; lane++) {
-               if (voltage_swing == VOLTAGE_LEVEL_3 ||
-                       dp->link_train.cr_loop[lane] == MAX_CR_LOOP)
-                       return -EINVAL;
-       }
-       return 0;
+       dp->link_train.lt_state = FAILED;
 }
 
 static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 {
-       u8 data;
-       u8 link_status[6];
+       u8 link_status[2];
        int lane;
        int lane_count;
-       u8 buf[5];
 
        u8 adjust_request[2];
        u8 voltage_swing;
@@ -488,98 +437,152 @@ static int exynos_dp_process_clock_recovery(struct exynos_dp_device *dp)
 
        usleep_range(100, 101);
 
-       exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
-                               6, link_status);
        lane_count = dp->link_train.lane_count;
 
+       exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
+                               2, link_status);
+
        if (exynos_dp_clock_recovery_ok(link_status, lane_count) == 0) {
                /* set training pattern 2 for EQ */
                exynos_dp_set_training_pattern(dp, TRAINING_PTN2);
 
-               adjust_request[0] = link_status[4];
-               adjust_request[1] = link_status[5];
+               for (lane = 0; lane < lane_count; lane++) {
+                       exynos_dp_read_bytes_from_dpcd(dp,
+                                       DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
+                                       2, adjust_request);
+                       voltage_swing = exynos_dp_get_adjust_request_voltage(
+                                                       adjust_request, lane);
+                       pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
+                                                       adjust_request, lane);
+                       training_lane = DPCD_VOLTAGE_SWING_SET(voltage_swing) |
+                                       DPCD_PRE_EMPHASIS_SET(pre_emphasis);
 
-               exynos_dp_get_adjust_train(dp, adjust_request);
+                       if (voltage_swing == VOLTAGE_LEVEL_3)
+                               training_lane |= DPCD_MAX_SWING_REACHED;
+                       if (pre_emphasis == PRE_EMPHASIS_LEVEL_3)
+                               training_lane |= DPCD_MAX_PRE_EMPHASIS_REACHED;
 
-               buf[0] = DPCD_SCRAMBLING_DISABLED |
-                        DPCD_TRAINING_PATTERN_2;
-               exynos_dp_write_byte_to_dpcd(dp,
-                       DPCD_ADDR_TRAINING_PATTERN_SET,
-                       buf[0]);
+                       dp->link_train.training_lane[lane] = training_lane;
 
-               for (lane = 0; lane < lane_count; lane++) {
                        exynos_dp_set_lane_link_training(dp,
                                dp->link_train.training_lane[lane],
                                lane);
-                       buf[lane] = dp->link_train.training_lane[lane];
-                       exynos_dp_write_byte_to_dpcd(dp,
-                               DPCD_ADDR_TRAINING_LANE0_SET + lane,
-                               buf[lane]);
                }
-               dp->link_train.lt_state = EQUALIZER_TRAINING;
-       } else {
-               exynos_dp_read_byte_from_dpcd(dp,
-                       DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
-                       &data);
-               adjust_request[0] = data;
 
-               exynos_dp_read_byte_from_dpcd(dp,
-                       DPCD_ADDR_ADJUST_REQUEST_LANE2_3,
-                       &data);
-               adjust_request[1] = data;
+               exynos_dp_write_byte_to_dpcd(dp,
+                       DPCD_ADDR_TRAINING_PATTERN_SET,
+                       DPCD_SCRAMBLING_DISABLED |
+                       DPCD_TRAINING_PATTERN_2);
+
+               exynos_dp_write_bytes_to_dpcd(dp,
+                       DPCD_ADDR_TRAINING_LANE0_SET,
+                       lane_count,
+                       dp->link_train.training_lane);
 
+               dev_info(dp->dev, "Link Training Clock Recovery success\n");
+               dp->link_train.lt_state = EQUALIZER_TRAINING;
+       } else {
                for (lane = 0; lane < lane_count; lane++) {
                        training_lane = exynos_dp_get_lane_link_training(
                                                        dp, lane);
+                       exynos_dp_read_bytes_from_dpcd(dp,
+                                       DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
+                                       2, adjust_request);
                        voltage_swing = exynos_dp_get_adjust_request_voltage(
                                                        adjust_request, lane);
                        pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
                                                        adjust_request, lane);
-                       if ((DPCD_VOLTAGE_SWING_GET(training_lane) == voltage_swing) &&
-                           (DPCD_PRE_EMPHASIS_GET(training_lane) == pre_emphasis))
-                               dp->link_train.cr_loop[lane]++;
-                       dp->link_train.training_lane[lane] = training_lane;
-               }
 
-               if (exynos_dp_check_max_cr_loop(dp, voltage_swing) != 0) {
-                       exynos_dp_reduce_link_rate(dp);
-               } else {
-                       exynos_dp_get_adjust_train(dp, adjust_request);
+                       if (voltage_swing == VOLTAGE_LEVEL_3 ||
+                           pre_emphasis == PRE_EMPHASIS_LEVEL_3) {
+                               dev_err(dp->dev, "voltage or pre emphasis reached max level\n");
+                               goto reduce_link_rate;
+                       }
 
-                       for (lane = 0; lane < lane_count; lane++) {
-                               exynos_dp_set_lane_link_training(dp,
-                                       dp->link_train.training_lane[lane],
-                                       lane);
-                               buf[lane] = dp->link_train.training_lane[lane];
-                               exynos_dp_write_byte_to_dpcd(dp,
-                                       DPCD_ADDR_TRAINING_LANE0_SET + lane,
-                                       buf[lane]);
+                       if ((DPCD_VOLTAGE_SWING_GET(training_lane) ==
+                                       voltage_swing) &&
+                          (DPCD_PRE_EMPHASIS_GET(training_lane) ==
+                                       pre_emphasis)) {
+                               dp->link_train.cr_loop[lane]++;
+                               if (dp->link_train.cr_loop[lane] == MAX_CR_LOOP) {
+                                       dev_err(dp->dev, "CR Max loop\n");
+                                       goto reduce_link_rate;
+                               }
                        }
+
+                       training_lane = DPCD_VOLTAGE_SWING_SET(voltage_swing) |
+                                       DPCD_PRE_EMPHASIS_SET(pre_emphasis);
+
+                       if (voltage_swing == VOLTAGE_LEVEL_3)
+                               training_lane |= DPCD_MAX_SWING_REACHED;
+                       if (pre_emphasis == PRE_EMPHASIS_LEVEL_3)
+                               training_lane |= DPCD_MAX_PRE_EMPHASIS_REACHED;
+
+                       dp->link_train.training_lane[lane] = training_lane;
+
+                       exynos_dp_set_lane_link_training(dp,
+                               dp->link_train.training_lane[lane], lane);
                }
+
+               exynos_dp_write_bytes_to_dpcd(dp,
+                       DPCD_ADDR_TRAINING_LANE0_SET,
+                       lane_count,
+                       dp->link_train.training_lane);
        }
 
        return 0;
+
+reduce_link_rate:
+       exynos_dp_reduce_link_rate(dp);
+       return -EIO;
 }
 
 static int exynos_dp_process_equalizer_training(struct exynos_dp_device *dp)
 {
-       u8 link_status[6];
+       u8 link_status[2];
+       u8 link_align[3];
        int lane;
        int lane_count;
-       u8 buf[5];
        u32 reg;
 
        u8 adjust_request[2];
+       u8 voltage_swing;
+       u8 pre_emphasis;
+       u8 training_lane;
 
        usleep_range(400, 401);
 
-       exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
-                               6, link_status);
        lane_count = dp->link_train.lane_count;
 
+       exynos_dp_read_bytes_from_dpcd(dp, DPCD_ADDR_LANE0_1_STATUS,
+                               2, link_status);
+
        if (exynos_dp_clock_recovery_ok(link_status, lane_count) == 0) {
-               adjust_request[0] = link_status[4];
-               adjust_request[1] = link_status[5];
+               link_align[0] = link_status[0];
+               link_align[1] = link_status[1];
+
+               exynos_dp_read_byte_from_dpcd(dp,
+                       DPCD_ADDR_LANE_ALIGN_STATUS_UPDATED,
+                       &link_align[2]);
+
+               for (lane = 0; lane < lane_count; lane++) {
+                       exynos_dp_read_bytes_from_dpcd(dp,
+                                       DPCD_ADDR_ADJUST_REQUEST_LANE0_1,
+                                       2, adjust_request);
+                       voltage_swing = exynos_dp_get_adjust_request_voltage(
+                                                       adjust_request, lane);
+                       pre_emphasis = exynos_dp_get_adjust_request_pre_emphasis(
+                                                       adjust_request, lane);
+                       training_lane = DPCD_VOLTAGE_SWING_SET(voltage_swing) |
+                                       DPCD_PRE_EMPHASIS_SET(pre_emphasis);
+
+                       if (voltage_swing == VOLTAGE_LEVEL_3)
+                               training_lane |= DPCD_MAX_SWING_REACHED;
+                       if (pre_emphasis == PRE_EMPHASIS_LEVEL_3)
+                               training_lane |= DPCD_MAX_PRE_EMPHASIS_REACHED;
+
+                       dp->link_train.training_lane[lane] = training_lane;
+               }
 
                if (exynos_dp_channel_eq_ok(link_status, lane_count) == 0) {
                        /* traing pattern Set to Normal */
@@ -596,39 +599,42 @@ static int exynos_dp_process_equalizer_training(struct exynos_dp_device *dp)
                        dp->link_train.lane_count = reg;
                        dev_dbg(dp->dev, "final lane count = %.2x\n",
                                dp->link_train.lane_count);
+
                        /* set enhanced mode if available */
                        exynos_dp_set_enhanced_mode(dp);
-
                        dp->link_train.lt_state = FINISHED;
                } else {
                        /* not all locked */
                        dp->link_train.eq_loop++;
 
                        if (dp->link_train.eq_loop > MAX_EQ_LOOP) {
-                               exynos_dp_reduce_link_rate(dp);
-                       } else {
-                               exynos_dp_get_adjust_train(dp, adjust_request);
-
-                               for (lane = 0; lane < lane_count; lane++) {
-                                       exynos_dp_set_lane_link_training(dp,
-                                               dp->link_train.training_lane[lane],
-                                               lane);
-                                       buf[lane] = dp->link_train.training_lane[lane];
-                                       exynos_dp_write_byte_to_dpcd(dp,
-                                               DPCD_ADDR_TRAINING_LANE0_SET + lane,
-                                               buf[lane]);
-                               }
+                               dev_err(dp->dev, "EQ Max loop\n");
+                               goto reduce_link_rate;
                        }
+
+                       for (lane = 0; lane < lane_count; lane++)
+                               exynos_dp_set_lane_link_training(dp,
+                                       dp->link_train.training_lane[lane],
+                                       lane);
+
+                       exynos_dp_write_bytes_to_dpcd(dp,
+                               DPCD_ADDR_TRAINING_LANE0_SET,
+                               lane_count,
+                               dp->link_train.training_lane);
                }
        } else {
-               exynos_dp_reduce_link_rate(dp);
+               goto reduce_link_rate;
        }
 
        return 0;
+
+reduce_link_rate:
+       exynos_dp_reduce_link_rate(dp);
+       return -EIO;
 }
 
 static void exynos_dp_get_max_rx_bandwidth(struct exynos_dp_device *dp,
-                       u8 *bandwidth)
+                                       u8 *bandwidth)
 {
        u8 data;
 
@@ -641,7 +647,7 @@ static void exynos_dp_get_max_rx_bandwidth(struct exynos_dp_device *dp,
 }
 
 static void exynos_dp_get_max_rx_lane_count(struct exynos_dp_device *dp,
-                       u8 *lane_count)
+                                       u8 *lane_count)
 {
        u8 data;
 
@@ -693,13 +699,7 @@ static void exynos_dp_init_training(struct exynos_dp_device *dp,
 static int exynos_dp_sw_link_training(struct exynos_dp_device *dp)
 {
        int retval = 0;
-       int training_finished;
-
-       /* Turn off unnecessary lane */
-       if (dp->link_train.lane_count == 1)
-               exynos_dp_set_analog_power_down(dp, CH1_BLOCK, 1);
-
-       training_finished = 0;
+       int training_finished = 0;
 
        dp->link_train.lt_state = START;
 
@@ -710,10 +710,14 @@ static int exynos_dp_sw_link_training(struct exynos_dp_device *dp)
                        exynos_dp_link_start(dp);
                        break;
                case CLOCK_RECOVERY:
-                       exynos_dp_process_clock_recovery(dp);
+                       retval = exynos_dp_process_clock_recovery(dp);
+                       if (retval)
+                               dev_err(dp->dev, "LT CR failed!\n");
                        break;
                case EQUALIZER_TRAINING:
-                       exynos_dp_process_equalizer_training(dp);
+                       retval = exynos_dp_process_equalizer_training(dp);
+                       if (retval)
+                               dev_err(dp->dev, "LT EQ failed!\n");
                        break;
                case FINISHED:
                        training_finished = 1;

diff --git a/drivers/video/exynos/exynos_dp_core.h b/drivers/video/exynos/exynos_dp_core.h
index 8526e54..44c11e1 100644 (file)
--- a/drivers/video/exynos/exynos_dp_core.h
+++ b/drivers/video/exynos/exynos_dp_core.h
@@ -144,7 +144,7 @@ void exynos_dp_disable_scrambling(struct exynos_dp_device *dp);
 #define DPCD_ADDR_TRAINING_PATTERN_SET         0x0102
 #define DPCD_ADDR_TRAINING_LANE0_SET           0x0103
 #define DPCD_ADDR_LANE0_1_STATUS               0x0202
-#define DPCD_ADDR_LANE_ALIGN__STATUS_UPDATED   0x0204
+#define DPCD_ADDR_LANE_ALIGN_STATUS_UPDATED    0x0204
 #define DPCD_ADDR_ADJUST_REQUEST_LANE0_1       0x0206
 #define DPCD_ADDR_ADJUST_REQUEST_LANE2_3       0x0207
 #define DPCD_ADDR_TEST_REQUEST                 0x0218