drm/dp_helper: Add Helpers for FRL Link Training support for DP-HDMI2.1 PCON

This patch adds support for configuring a PCON device,
connected as a DP branched device to enable FRL Link training
with a HDMI2.1 + sink.

v2: Fixed typos and addressed other review comments from Uma Shankar.
-changed the commit message for better clarity (Uma Shankar)
-removed unnecessary argument supplied to a drm helper function.
-fixed return value for max frl read from pcon.

v3: Removed DPCD 0x3035 for MAX Sink FRL b/w as per new version of spec.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com> (v2)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201218103723.30844-5-ankit.k.nautiyal@intel.com

1 files changed, 263 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 37ec3b94389c..5890e0ba2eb9 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -2596,3 +2596,266 @@ void drm_dp_vsc_sdp_log(const char *level, struct device *dev,
 #undef DP_SDP_LOG
 }
 EXPORT_SYMBOL(drm_dp_vsc_sdp_log);
+
+/**
+ * drm_dp_get_pcon_max_frl_bw() - maximum frl supported by PCON
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: port capabilities
+ *
+ * Returns maximum frl bandwidth supported by PCON in GBPS,
+ * returns 0 if not supported.
+ */
+int drm_dp_get_pcon_max_frl_bw(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
+			       const u8 port_cap[4])
+{
+	int bw;
+	u8 buf;
+
+	buf = port_cap[2];
+	bw = buf & DP_PCON_MAX_FRL_BW;
+
+	switch (bw) {
+	case DP_PCON_MAX_9GBPS:
+		return 9;
+	case DP_PCON_MAX_18GBPS:
+		return 18;
+	case DP_PCON_MAX_24GBPS:
+		return 24;
+	case DP_PCON_MAX_32GBPS:
+		return 32;
+	case DP_PCON_MAX_40GBPS:
+		return 40;
+	case DP_PCON_MAX_48GBPS:
+		return 48;
+	case DP_PCON_MAX_0GBPS:
+	default:
+		return 0;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_get_pcon_max_frl_bw);
+
+/**
+ * drm_dp_pcon_frl_prepare() - Prepare PCON for FRL.
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 if success, else returns negative error code.
+ */
+int drm_dp_pcon_frl_prepare(struct drm_dp_aux *aux, bool enable_frl_ready_hpd)
+{
+	int ret;
+	u8 buf = DP_PCON_ENABLE_SOURCE_CTL_MODE |
+		 DP_PCON_ENABLE_LINK_FRL_MODE;
+
+	if (enable_frl_ready_hpd)
+		buf |= DP_PCON_ENABLE_HPD_READY;
+
+	ret = drm_dp_dpcd_writeb(aux, DP_PCON_HDMI_LINK_CONFIG_1, buf);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_dp_pcon_frl_prepare);
+
+/**
+ * drm_dp_pcon_is_frl_ready() - Is PCON ready for FRL
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns true if success, else returns false.
+ */
+bool drm_dp_pcon_is_frl_ready(struct drm_dp_aux *aux)
+{
+	int ret;
+	u8 buf;
+
+	ret = drm_dp_dpcd_readb(aux, DP_PCON_HDMI_TX_LINK_STATUS, &buf);
+	if (ret < 0)
+		return false;
+
+	if (buf & DP_PCON_FRL_READY)
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL(drm_dp_pcon_is_frl_ready);
+
+/**
+ * drm_dp_pcon_frl_configure_1() - Set HDMI LINK Configuration-Step1
+ * @aux: DisplayPort AUX channel
+ * @max_frl_gbps: maximum frl bw to be configured between PCON and HDMI sink
+ * @concurrent_mode: true if concurrent mode or operation is required,
+ * false otherwise.
+ *
+ * Returns 0 if success, else returns negative error code.
+ */
+
+int drm_dp_pcon_frl_configure_1(struct drm_dp_aux *aux, int max_frl_gbps,
+				bool concurrent_mode)
+{
+	int ret;
+	u8 buf;
+
+	ret = drm_dp_dpcd_readb(aux, DP_PCON_HDMI_LINK_CONFIG_1, &buf);
+	if (ret < 0)
+		return ret;
+
+	if (concurrent_mode)
+		buf |= DP_PCON_ENABLE_CONCURRENT_LINK;
+	else
+		buf &= ~DP_PCON_ENABLE_CONCURRENT_LINK;
+
+	switch (max_frl_gbps) {
+	case 9:
+		buf |=  DP_PCON_ENABLE_MAX_BW_9GBPS;
+		break;
+	case 18:
+		buf |=  DP_PCON_ENABLE_MAX_BW_18GBPS;
+		break;
+	case 24:
+		buf |=  DP_PCON_ENABLE_MAX_BW_24GBPS;
+		break;
+	case 32:
+		buf |=  DP_PCON_ENABLE_MAX_BW_32GBPS;
+		break;
+	case 40:
+		buf |=  DP_PCON_ENABLE_MAX_BW_40GBPS;
+		break;
+	case 48:
+		buf |=  DP_PCON_ENABLE_MAX_BW_48GBPS;
+		break;
+	case 0:
+		buf |=  DP_PCON_ENABLE_MAX_BW_0GBPS;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	ret = drm_dp_dpcd_writeb(aux, DP_PCON_HDMI_LINK_CONFIG_1, buf);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_pcon_frl_configure_1);
+
+/**
+ * drm_dp_pcon_frl_configure_2() - Set HDMI Link configuration Step-2
+ * @aux: DisplayPort AUX channel
+ * @max_frl_mask : Max FRL BW to be tried by the PCON with HDMI Sink
+ * @extended_train_mode : true for Extended Mode, false for Normal Mode.
+ * In Normal mode, the PCON tries each frl bw from the max_frl_mask starting
+ * from min, and stops when link training is successful. In Extended mode, all
+ * frl bw selected in the mask are trained by the PCON.
+ *
+ * Returns 0 if success, else returns negative error code.
+ */
+int drm_dp_pcon_frl_configure_2(struct drm_dp_aux *aux, int max_frl_mask,
+				bool extended_train_mode)
+{
+	int ret;
+	u8 buf = max_frl_mask;
+
+	if (extended_train_mode)
+		buf |= DP_PCON_FRL_LINK_TRAIN_EXTENDED;
+
+	ret = drm_dp_dpcd_writeb(aux, DP_PCON_HDMI_LINK_CONFIG_2, buf);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_pcon_frl_configure_2);
+
+/**
+ * drm_dp_pcon_reset_frl_config() - Re-Set HDMI Link configuration.
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 if success, else returns negative error code.
+ */
+int drm_dp_pcon_reset_frl_config(struct drm_dp_aux *aux)
+{
+	int ret;
+
+	ret = drm_dp_dpcd_writeb(aux, DP_PCON_HDMI_LINK_CONFIG_1, 0x0);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_pcon_reset_frl_config);
+
+/**
+ * drm_dp_pcon_frl_enable() - Enable HDMI link through FRL
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns 0 if success, else returns negative error code.
+ */
+int drm_dp_pcon_frl_enable(struct drm_dp_aux *aux)
+{
+	int ret;
+	u8 buf = 0;
+
+	ret = drm_dp_dpcd_readb(aux, DP_PCON_HDMI_LINK_CONFIG_1, &buf);
+	if (ret < 0)
+		return ret;
+	if (!(buf & DP_PCON_ENABLE_SOURCE_CTL_MODE)) {
+		DRM_DEBUG_KMS("PCON in Autonomous mode, can't enable FRL\n");
+		return -EINVAL;
+	}
+	buf |= DP_PCON_ENABLE_HDMI_LINK;
+	ret = drm_dp_dpcd_writeb(aux, DP_PCON_HDMI_LINK_CONFIG_1, buf);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_pcon_frl_enable);
+
+/**
+ * drm_dp_pcon_hdmi_link_active() - check if the PCON HDMI LINK status is active.
+ * @aux: DisplayPort AUX channel
+ *
+ * Returns true if link is active else returns false.
+ */
+bool drm_dp_pcon_hdmi_link_active(struct drm_dp_aux *aux)
+{
+	u8 buf;
+	int ret;
+
+	ret = drm_dp_dpcd_readb(aux, DP_PCON_HDMI_TX_LINK_STATUS, &buf);
+	if (ret < 0)
+		return false;
+
+	return buf & DP_PCON_HDMI_TX_LINK_ACTIVE;
+}
+EXPORT_SYMBOL(drm_dp_pcon_hdmi_link_active);
+
+/**
+ * drm_dp_pcon_hdmi_link_mode() - get the PCON HDMI LINK MODE
+ * @aux: DisplayPort AUX channel
+ * @frl_trained_mask: pointer to store bitmask of the trained bw configuration.
+ * Valid only if the MODE returned is FRL. For Normal Link training mode
+ * only 1 of the bits will be set, but in case of Extended mode, more than
+ * one bits can be set.
+ *
+ * Returns the link mode : TMDS or FRL on success, else returns negative error
+ * code.
+ */
+int drm_dp_pcon_hdmi_link_mode(struct drm_dp_aux *aux, u8 *frl_trained_mask)
+{
+	u8 buf;
+	int mode;
+	int ret;
+
+	ret = drm_dp_dpcd_readb(aux, DP_PCON_HDMI_POST_FRL_STATUS, &buf);
+	if (ret < 0)
+		return ret;
+
+	mode = buf & DP_PCON_HDMI_LINK_MODE;
+
+	if (frl_trained_mask && DP_PCON_HDMI_MODE_FRL == mode)
+		*frl_trained_mask = (buf & DP_PCON_HDMI_FRL_TRAINED_BW) >> 1;
+
+	return mode;
+}
+EXPORT_SYMBOL(drm_dp_pcon_hdmi_link_mode);