From: Thierry Reding treding@nvidia.com
Add a helper that will perform link training as described in the DisplayPort specification.
Signed-off-by: Thierry Reding treding@nvidia.com --- drivers/gpu/drm/drm_dp_helper.c | 476 +++++++++++++++++++++++++++++++++++++++- include/drm/drm_dp_helper.h | 49 +++++ 2 files changed, 524 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 543349e14481..8968201ea93c 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -292,6 +292,19 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, } EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
+static void drm_dp_link_reset(struct drm_dp_link *link) +{ + if (!link) + return; + + link->revision = 0; + link->edp = 0; + link->rate = 0; + link->num_lanes = 0; + link->capabilities = 0; + link->aux_rd_interval = 0; +} + /** * drm_dp_link_probe() - probe a DisplayPort link for capabilities * @aux: DisplayPort AUX channel @@ -308,7 +321,7 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link) u8 values[16], value; int err;
- memset(link, 0, sizeof(*link)); + drm_dp_link_reset(link);
err = drm_dp_dpcd_read(aux, DP_DPCD_REV, values, sizeof(values)); if (err < 0) @@ -451,6 +464,14 @@ int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link) u8 values[2], value = 0; int err;
+ if (link->ops && link->ops->configure) { + err = link->ops->configure(link); + if (err < 0) { + DRM_ERROR("failed to configure DP link: %d\n", err); + return err; + } + } + values[0] = drm_dp_link_rate_to_bw_code(link->rate); values[1] = link->num_lanes;
@@ -727,3 +748,456 @@ void drm_dp_aux_unregister(struct drm_dp_aux *aux) i2c_del_adapter(&aux->ddc); } EXPORT_SYMBOL(drm_dp_aux_unregister); + +/** + * DOC: Link training + * + * These functions contain common logic and helpers to implement DisplayPort + * link training. + */ + +/** + * drm_dp_link_train_init() - initialize DisplayPort link training state + * @train: DisplayPort link training state + */ +void drm_dp_link_train_init(struct drm_dp_link_train *train) +{ + struct drm_dp_link_train_set *request = &train->request; + struct drm_dp_link_train_set *adjust = &train->adjust; + unsigned int i; + + for (i = 0; i < 4; i++) { + request->voltage_swing[i] = 0; + adjust->voltage_swing[i] = 0; + + request->pre_emphasis[i] = 0; + adjust->pre_emphasis[i] = 0; + + request->post_cursor[i] = 0; + adjust->post_cursor[i] = 0; + } + + train->pattern = DP_TRAINING_PATTERN_DISABLE; + train->clock_recovered = false; + train->channel_equalized = false; +} + +static bool drm_dp_link_train_valid(const struct drm_dp_link_train *train) +{ + return train->clock_recovered && train->channel_equalized; +} + +static int drm_dp_link_apply_training(struct drm_dp_link *link) +{ + struct drm_dp_link_train_set *request = &link->train.request; + unsigned int lanes = link->num_lanes, *vs, *pe, *pc, i; + struct drm_dp_aux *aux = link->aux; + u8 values[4], pattern = 0; + int err; + + err = link->ops->apply_training(link); + if (err < 0) { + DRM_ERROR("failed to apply link training: %d\n", err); + return err; + } + + vs = request->voltage_swing; + pe = request->pre_emphasis; + pc = request->post_cursor; + + /* write currently selected voltage-swing and pre-emphasis levels */ + for (i = 0; i < lanes; i++) + values[i] = DP_TRAIN_VOLTAGE_SWING_LEVEL(vs[i]) | + DP_TRAIN_PRE_EMPHASIS_LEVEL(pe[i]); + + err = drm_dp_dpcd_write(aux, DP_TRAINING_LANE0_SET, values, lanes); + if (err < 0) { + DRM_ERROR("failed to set training parameters: %d\n", err); + return err; + } + + /* write currently selected post-cursor level (if supported) */ + if (link->revision >= 0x12 && link->rate == 540000) { + values[0] = values[1] = 0; + + for (i = 0; i < lanes; i++) + values[i / 2] |= DP_LANE_POST_CURSOR(i, pc[i]); + + err = drm_dp_dpcd_write(aux, DP_TRAINING_LANE0_1_SET2, values, + DIV_ROUND_UP(lanes, 2)); + if (err < 0) { + DRM_ERROR("failed to set post-cursor: %d\n", err); + return err; + } + } + + /* write link pattern */ + if (link->train.pattern != DP_TRAINING_PATTERN_DISABLE) + pattern |= DP_LINK_SCRAMBLING_DISABLE; + + pattern |= link->train.pattern; + + err = drm_dp_dpcd_writeb(aux, DP_TRAINING_PATTERN_SET, pattern); + if (err < 0) { + DRM_ERROR("failed to set training pattern: %d\n", err); + return err; + } + + return 0; +} + +static void drm_dp_link_train_wait(struct drm_dp_link *link) +{ + unsigned long min = 0; + + if (link->aux_rd_interval == 0) { + switch (link->train.pattern) { + case DP_TRAINING_PATTERN_1: + min = 100; + break; + + case DP_TRAINING_PATTERN_2: + case DP_TRAINING_PATTERN_3: + min = 400; + break; + + default: + break; + } + } else { + min = link->aux_rd_interval; + } + + if (min > 0) + usleep_range(min, 2 * min); +} + +static void drm_dp_link_get_adjustments(struct drm_dp_link *link, + u8 status[DP_LINK_STATUS_SIZE]) +{ + struct drm_dp_link_train_set *adjust = &link->train.adjust; + unsigned int i; + + for (i = 0; i < link->num_lanes; i++) { + adjust->voltage_swing[i] = + drm_dp_get_adjust_request_voltage(status, i) >> + DP_TRAIN_VOLTAGE_SWING_SHIFT; + + adjust->pre_emphasis[i] = + drm_dp_get_adjust_request_pre_emphasis(status, i) >> + DP_TRAIN_PRE_EMPHASIS_SHIFT; + + adjust->post_cursor[i] = + drm_dp_get_adjust_request_post_cursor(status, i); + } +} + +static void drm_dp_link_train_adjust(struct drm_dp_link_train *train) +{ + struct drm_dp_link_train_set *request = &train->request; + struct drm_dp_link_train_set *adjust = &train->adjust; + unsigned int i; + + for (i = 0; i < 4; i++) + if (request->voltage_swing[i] != adjust->voltage_swing[i]) + request->voltage_swing[i] = adjust->voltage_swing[i]; + + for (i = 0; i < 4; i++) + if (request->pre_emphasis[i] != adjust->pre_emphasis[i]) + request->pre_emphasis[i] = adjust->pre_emphasis[i]; + + for (i = 0; i < 4; i++) + if (request->post_cursor[i] != adjust->post_cursor[i]) + request->post_cursor[i] = adjust->post_cursor[i]; +} + +static int drm_dp_link_recover_clock(struct drm_dp_link *link) +{ + u8 status[DP_LINK_STATUS_SIZE]; + int err; + + err = drm_dp_link_apply_training(link); + if (err < 0) + return err; + + drm_dp_link_train_wait(link); + + err = drm_dp_dpcd_read_link_status(link->aux, status); + if (err < 0) { + DRM_ERROR("failed to read link status: %d\n", err); + return err; + } + + if (!drm_dp_clock_recovery_ok(status, link->num_lanes)) + drm_dp_link_get_adjustments(link, status); + else + link->train.clock_recovered = true; + + return 0; +} + +static int drm_dp_link_clock_recovery(struct drm_dp_link *link) +{ + unsigned int repeat; + int err; + + /* start clock recovery using training pattern 1 */ + link->train.pattern = DP_TRAINING_PATTERN_1; + + for (repeat = 1; repeat < 5; repeat++) { + err = drm_dp_link_recover_clock(link); + if (err < 0) { + DRM_ERROR("failed to recover clock: %d\n", err); + return err; + } + + drm_dp_link_train_adjust(&link->train); + + if (link->train.clock_recovered) + break; + } + + return 0; +} + +static int drm_dp_link_equalize_channel(struct drm_dp_link *link) +{ + struct drm_dp_aux *aux = link->aux; + u8 status[DP_LINK_STATUS_SIZE]; + int err; + + err = drm_dp_link_apply_training(link); + if (err < 0) + return err; + + drm_dp_link_train_wait(link); + + err = drm_dp_dpcd_read_link_status(aux, status); + if (err < 0) { + DRM_ERROR("failed to read link status: %d\n", err); + return err; + } + + if (!drm_dp_clock_recovery_ok(status, link->num_lanes)) { + DRM_ERROR("clock recovery lost while equalizing channel\n"); + link->train.clock_recovered = false; + return 0; + } + + if (!drm_dp_channel_eq_ok(status, link->num_lanes)) + drm_dp_link_get_adjustments(link, status); + else + link->train.channel_equalized = true; + + return 0; +} + +static int drm_dp_link_channel_equalization(struct drm_dp_link *link) +{ + unsigned int repeat; + int err; + + /* start channel equalization using pattern 2 or 3 */ + if (link->capabilities & DP_LINK_CAP_TPS3) + link->train.pattern = DP_TRAINING_PATTERN_3; + else + link->train.pattern = DP_TRAINING_PATTERN_2; + + for (repeat = 1; repeat < 5; repeat++) { + err = drm_dp_link_equalize_channel(link); + if (err < 0) { + DRM_ERROR("failed to equalize channel: %d\n", err); + return err; + } + + drm_dp_link_train_adjust(&link->train); + + if (link->train.channel_equalized) + break; + } + + return 0; +} + +static int drm_dp_link_downgrade(struct drm_dp_link *link) +{ + switch (link->rate) { + case 162000: + return -EINVAL; + + case 270000: + link->rate = 162000; + break; + + case 540000: + link->rate = 270000; + return 0; + } + + return 0; +} + +static void drm_dp_link_train_disable(struct drm_dp_link *link) +{ + int err; + + link->train.pattern = DP_TRAINING_PATTERN_DISABLE; + + err = drm_dp_link_apply_training(link); + if (err < 0) + DRM_ERROR("failed to disable link training: %d\n", err); +} + +static int drm_dp_link_train_full(struct drm_dp_link *link) +{ + int err; + +retry: + DRM_DEBUG_KMS("full-training link: %u lane%s at %u MHz\n", + link->num_lanes, (link->num_lanes > 1) ? "s" : "", + link->rate / 100); + + err = drm_dp_link_configure(link->aux, link); + if (err < 0) { + DRM_ERROR("failed to configure DP link: %d\n", err); + return err; + } + + err = drm_dp_link_clock_recovery(link); + if (err < 0) { + DRM_ERROR("clock recovery failed: %d\n", err); + goto out; + } + + if (!link->train.clock_recovered) { + DRM_ERROR("clock recovery failed, downgrading link\n"); + + err = drm_dp_link_downgrade(link); + if (err < 0) + goto out; + + goto retry; + } + + DRM_DEBUG_KMS("clock recovery succeeded\n"); + + err = drm_dp_link_channel_equalization(link); + if (err < 0) { + DRM_ERROR("channel equalization failed: %d\n", err); + goto out; + } + + if (!link->train.channel_equalized) { + DRM_ERROR("channel equalization failed, downgrading link\n"); + + err = drm_dp_link_downgrade(link); + if (err < 0) + goto out; + + goto retry; + } + + DRM_DEBUG_KMS("channel equalization succeeded\n"); + +out: + drm_dp_link_train_disable(link); + return err; +} + +static int drm_dp_link_train_fast(struct drm_dp_link *link) +{ + u8 status[DP_LINK_STATUS_SIZE]; + int err; + + DRM_DEBUG_KMS("fast-training link: %u lane%s at %u MHz\n", + link->num_lanes, (link->num_lanes > 1) ? "s" : "", + link->rate / 100); + + err = drm_dp_link_configure(link->aux, link); + if (err < 0) { + DRM_ERROR("failed to configure DP link: %d\n", err); + return err; + } + + /* transmit training pattern 1 for 500 microseconds */ + link->train.pattern = DP_TRAINING_PATTERN_1; + + err = drm_dp_link_apply_training(link); + if (err < 0) + goto out; + + usleep_range(500, 1000); + + /* transmit training pattern 2 or 3 for 500 microseconds */ + if (link->capabilities & DP_LINK_CAP_TPS3) + link->train.pattern = DP_TRAINING_PATTERN_3; + else + link->train.pattern = DP_TRAINING_PATTERN_2; + + err = drm_dp_link_apply_training(link); + if (err < 0) + goto out; + + usleep_range(500, 1000); + + err = drm_dp_dpcd_read_link_status(link->aux, status); + if (err < 0) { + DRM_ERROR("failed to read link status: %d\n", err); + goto out; + } + + if (!drm_dp_clock_recovery_ok(status, link->num_lanes)) { + DRM_ERROR("clock recovery failed\n"); + err = -EIO; + } + + if (!drm_dp_channel_eq_ok(status, link->num_lanes)) { + DRM_ERROR("channel equalization failed\n"); + err = -EIO; + } + +out: + drm_dp_link_train_disable(link); + return err; +} + +/** + * drm_dp_link_train() - perform DisplayPort link training + * @link: a DP link object + * + * Uses the context stored in the DP link object to perform link training. It + * is expected that drivers will call drm_dp_link_probe() to obtain the link + * capabilities before performing link training. + * + * If the sink supports fast link training (no AUX CH handshake) and valid + * training settings are available, this function will try to perform fast + * link training and fall back to full link training on failure. + * + * Returns: 0 on success or a negative error code on failure. + */ +int drm_dp_link_train(struct drm_dp_link *link) +{ + int err; + + if (link->capabilities & DP_LINK_CAP_FAST_TRAINING) { + if (drm_dp_link_train_valid(&link->train)) { + err = drm_dp_link_train_fast(link); + if (err < 0) + DRM_ERROR("fast link training failed: %d\n", + err); + else + return 0; + } else { + DRM_DEBUG_KMS("training parameters not available\n"); + } + } else { + DRM_DEBUG_KMS("fast link training not supported\n"); + } + + err = drm_dp_link_train_full(link); + if (err < 0) + DRM_ERROR("full link training failed: %d\n", err); + + return err; +} +EXPORT_SYMBOL(drm_dp_link_train); diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 600347f8cdd4..d041bb00d6a0 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -265,12 +265,14 @@ # define DP_TRAIN_VOLTAGE_SWING_LEVEL_1 (1 << 0) # define DP_TRAIN_VOLTAGE_SWING_LEVEL_2 (2 << 0) # define DP_TRAIN_VOLTAGE_SWING_LEVEL_3 (3 << 0) +# define DP_TRAIN_VOLTAGE_SWING_LEVEL(x) ((x) << 0)
# define DP_TRAIN_PRE_EMPHASIS_MASK (3 << 3) # define DP_TRAIN_PRE_EMPH_LEVEL_0 (0 << 3) # define DP_TRAIN_PRE_EMPH_LEVEL_1 (1 << 3) # define DP_TRAIN_PRE_EMPH_LEVEL_2 (2 << 3) # define DP_TRAIN_PRE_EMPH_LEVEL_3 (3 << 3) +# define DP_TRAIN_PRE_EMPHASIS_LEVEL(x) ((x) << 3)
# define DP_TRAIN_PRE_EMPHASIS_SHIFT 3 # define DP_TRAIN_MAX_PRE_EMPHASIS_REACHED (1 << 5) @@ -308,6 +310,7 @@ # define DP_LANE02_MAX_POST_CURSOR2_REACHED (1 << 2) # define DP_LANE13_POST_CURSOR2_SET_MASK (3 << 4) # define DP_LANE13_MAX_POST_CURSOR2_REACHED (1 << 6) +# define DP_LANE_POST_CURSOR(i, x) (((x) & 0x3) << (((i) & 1) << 2))
#define DP_MSTM_CTRL 0x111 /* 1.2 */ # define DP_MST_EN (1 << 0) @@ -751,6 +754,45 @@ static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux, int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux, u8 status[DP_LINK_STATUS_SIZE]);
+/** + * struct drm_dp_link_train_set - link training settings + * @voltage_swing: per-lane voltage swing + * @pre_emphasis: per-lane pre-emphasis + * @post_cursor: per-lane post-cursor + */ +struct drm_dp_link_train_set { + unsigned int voltage_swing[4]; + unsigned int pre_emphasis[4]; + unsigned int post_cursor[4]; +}; + +/** + * struct drm_dp_link_train - link training state information + * @request: currently requested settings + * @adjust: adjustments requested by sink + * @pattern: currently requested training pattern + * @clock_recovered: flag to track if clock recovery has completed + * @channel_equalized: flag to track if channel equalization has completed + */ +struct drm_dp_link_train { + struct drm_dp_link_train_set request; + struct drm_dp_link_train_set adjust; + + unsigned int pattern; + + bool clock_recovered; + bool channel_equalized; +}; + +void drm_dp_link_train_init(struct drm_dp_link_train *train); + +struct drm_dp_link; + +struct drm_dp_link_ops { + int (*apply_training)(struct drm_dp_link *link); + int (*configure)(struct drm_dp_link *link); +}; + /* * DisplayPort link */ @@ -767,6 +809,11 @@ struct drm_dp_link { unsigned int num_lanes; unsigned long capabilities; unsigned long aux_rd_interval; + + const struct drm_dp_link_ops *ops; + struct drm_dp_aux *aux; + + struct drm_dp_link_train train; };
int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link); @@ -774,6 +821,8 @@ int drm_dp_link_power_up(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_power_down(struct drm_dp_aux *aux, struct drm_dp_link *link); int drm_dp_link_configure(struct drm_dp_aux *aux, struct drm_dp_link *link);
+int drm_dp_link_train(struct drm_dp_link *link); + int drm_dp_aux_register(struct drm_dp_aux *aux); void drm_dp_aux_unregister(struct drm_dp_aux *aux);