[RFC PATCH] drm/bridge: add support for FEC in mhdp8546 driver
Damian Kos
dkos at cadence.com
Tue Nov 6 14:47:20 UTC 2018
From: Przemyslaw Gaj <pgaj at cadence.com>
This patch enables FEC (Forward Error Correction) on Cadence DisplayPort
controller if it's supported by the Sink.
This patch is an addition to patch with mhdp8546 driver @
patchwork.kernel.org/cover/10632065/
Signed-off-by: Przemyslaw Gaj <pgaj at cadence.com>
Signed-off-by: Damian Kos <dkos at cadence.com>
---
drivers/gpu/drm/bridge/cdns-mhdp.c | 138 ++++++++++++++++++++++++++
drivers/gpu/drm/bridge/cdns-mhdp.h | 4 +-
include/drm/bridge/cdns-mhdp-common.h | 2 +
3 files changed, 143 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/cdns-mhdp.c b/drivers/gpu/drm/bridge/cdns-mhdp.c
index caaf3c17d74f..3bfe1eda1468 100644
--- a/drivers/gpu/drm/bridge/cdns-mhdp.c
+++ b/drivers/gpu/drm/bridge/cdns-mhdp.c
@@ -392,6 +392,127 @@ static void mhdp_adjust_requested_eq(struct cdns_mhdp_device *mhdp,
}
}
+static int cdns_mhdp_wait_for_fec(struct cdns_mhdp_device *mhdp,
+ bool expected_status)
+{
+ u32 fec_status;
+ unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+
+ cdns_mhdp_reg_read(mhdp, CDNS_DP_FEC_STATUS, &fec_status);
+ while (((fec_status & CDNS_DP_FEC_BUSY) != expected_status) &&
+ time_before(jiffies, timeout)) {
+ cdns_mhdp_reg_read(mhdp, CDNS_DP_FEC_STATUS, &fec_status);
+ cpu_relax();
+ }
+
+ if (time_after_eq(jiffies, timeout)) {
+ DRM_DEV_ERROR(mhdp->dev, "Timeout while waiting for FEC\n");
+ return -ETIMEDOUT;
+ }
+
+ return 0;
+}
+
+static int cdns_mhdp_fec_sink_support(struct cdns_mhdp_device *mhdp)
+{
+ int ret;
+ u16 dpcd_buffer;
+
+ ret = drm_dp_dpcd_read(&mhdp->aux, DP_FEC_CAPABILITY, &dpcd_buffer, 1);
+ if (ret)
+ return ret;
+
+ if (!(dpcd_buffer & DP_FEC_CAPABLE)) {
+ ret = -ENOTSUPP;
+ DRM_DEV_ERROR(mhdp->dev, "sink does not support FEC: %d\n",
+ ret);
+ goto err;
+ }
+
+ ret = 0;
+
+err:
+ return ret;
+}
+
+static int cdns_mhdp_fec_sink_set_ready(struct cdns_mhdp_device *mhdp,
+ bool enable)
+{
+ int ret;
+ u16 dpcd_buffer;
+
+ ret = drm_dp_dpcd_read(&mhdp->aux, DP_FEC_CONFIGURATION,
+ &dpcd_buffer, 1);
+ if (ret)
+ goto err;
+
+ if (enable)
+ dpcd_buffer |= DP_FEC_READY;
+ else
+ dpcd_buffer &= ~DP_FEC_READY;
+
+ ret = drm_dp_dpcd_write(&mhdp->aux, DP_FEC_CONFIGURATION,
+ &dpcd_buffer, 1);
+ if (ret)
+ return 0;
+
+err:
+ DRM_DEV_ERROR(mhdp->dev, "cannot set sink FEC ready: %d\n", ret);
+ return -EIO;
+}
+
+static int cdns_mhdp_fec_set_ready(struct cdns_mhdp_device *mhdp, bool enable)
+{
+ int ret;
+
+ ret = cdns_mhdp_fec_sink_support(mhdp);
+ if (ret)
+ goto err;
+
+ ret = cdns_mhdp_fec_sink_set_ready(mhdp, enable);
+ if (ret)
+ goto err;
+
+ ret = cdns_mhdp_reg_write_bit(mhdp, CDNS_DP_FEC_CTRL, 1, 1, enable);
+ if (ret)
+ goto err;
+
+ return 0;
+err:
+ return ret;
+}
+
+static int cdns_mhdp_fec_enable(struct cdns_mhdp_device *mhdp, bool enable)
+{
+ int ret;
+ u32 resp;
+ unsigned int dp_framer_global_config;
+
+ if (mhdp->fec_enabled == enable) {
+ ret = -EEXIST;
+ goto err;
+ }
+
+ ret = cdns_mhdp_reg_read(mhdp, DP_FRAMER_GLOBAL_CONFIG, &resp);
+ if (ret)
+ goto err;
+
+ dp_framer_global_config = be32_to_cpu(resp);
+ pr_err("0x%.8x\n", dp_framer_global_config);
+ if (!(dp_framer_global_config & CDNS_DP_NO_VIDEO_MODE)) {
+ ret = -EIO;
+ goto err;
+ }
+
+ ret = cdns_mhdp_reg_write_bit(mhdp, CDNS_DP_FEC_CTRL, 0, 1, enable);
+
+ return cdns_mhdp_wait_for_fec(mhdp, enable);
+err:
+ DRM_DEV_ERROR(mhdp->dev, "set fec enable failed: %d\n", ret);
+ return ret;
+}
+
+
static bool mhdp_link_training_channel_eq(struct cdns_mhdp_device *mhdp,
u8 eq_tps,
unsigned int training_interval)
@@ -769,6 +890,13 @@ static int cdns_mhdp_link_up(struct cdns_mhdp_device *mhdp)
amp[1] = DP_SET_ANSI_8B10B;
drm_dp_dpcd_write(&mhdp->aux, DP_DOWNSPREAD_CTRL, amp, 2);
+ if (cdns_mhdp_fec_set_ready(mhdp, true)) {
+ mhdp->fec_enabled = false;
+ dev_info(mhdp->dev, "Cannot set FEC ready.\n");
+ } else {
+ mhdp->fec_enabled = true;
+ }
+
if (mhdp->host.fast_link & mhdp->sink.fast_link) {
/* FIXME: implement fastlink */
dev_dbg(mhdp->dev, "fastlink\n");
@@ -807,6 +935,14 @@ static int cdns_mhdp_sst_enable(struct drm_bridge *bridge)
pxlfmt = cdns_mhdp_get_pxlfmt(disp_info->color_formats);
bpp = cdns_mhdp_get_bpp(disp_info->bpc, pxlfmt);
+ if (mhdp->fec_enabled && cdns_mhdp_fec_enable(mhdp, true)) {
+ mhdp->fec_enabled = false;
+ dev_info(mhdp->dev, "Cannot enable FEC.\n");
+ } else {
+ mhdp->fec_enabled = true;
+ }
+
+
/* find optimal tu_size */
required_bandwidth = pxlclock * bpp / 8;
available_bandwidth = mhdp->link.num_lanes * rate;
@@ -814,6 +950,8 @@ static int cdns_mhdp_sst_enable(struct drm_bridge *bridge)
tu_size += 2;
vs_f = tu_size * required_bandwidth / available_bandwidth;
+ if (mhdp->fec_enabled)
+ vs_f = (vs_f * 1024) / 1000; // 102.4 percent
vs = vs_f / 1000;
vs_f = vs_f % 1000;
/*
diff --git a/drivers/gpu/drm/bridge/cdns-mhdp.h b/drivers/gpu/drm/bridge/cdns-mhdp.h
index abc1fa3f51a6..ba233adf9fe7 100644
--- a/drivers/gpu/drm/bridge/cdns-mhdp.h
+++ b/drivers/gpu/drm/bridge/cdns-mhdp.h
@@ -179,7 +179,9 @@
#define CDNS_DP_LANE_EN (CDNS_DPTX_GLOBAL + 0x00)
#define CDNS_DP_LANE_EN_LANES(x) GENMASK(x - 1, 0)
#define CDNS_DP_ENHNCD (CDNS_DPTX_GLOBAL + 0x04)
-
+#define CDNS_DP_FEC_CTRL (CDNS_DPTX_GLOBAL + 0x10)
+#define CDNS_DP_FEC_STATUS (CDNS_DPTX_GLOBAL + 0x14)
+#define CDNS_DP_FEC_BUSY BIT(0)
#define to_mhdp_connector(x) container_of(x, struct cdns_mhdp_connector, base)
#define to_mhdp_bridge(x) container_of(x, struct cdns_mhdp_bridge, base)
diff --git a/include/drm/bridge/cdns-mhdp-common.h b/include/drm/bridge/cdns-mhdp-common.h
index 1e8a44138ce2..52feeca3a914 100644
--- a/include/drm/bridge/cdns-mhdp-common.h
+++ b/include/drm/bridge/cdns-mhdp-common.h
@@ -566,6 +566,8 @@ struct cdns_mhdp_device {
bool can_mst;
bool link_up;
bool plugged;
+
+ bool fec_enabled;
};
void cdns_mhdp_clock_reset(struct cdns_mhdp_device *mhdp);
--
2.17.1
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