[PATCH RFC 20/25] drm/connector: hdmi: Add QMS state validation and computation

[Nicolas Frattaroli]

Add the necessary code to the HDMI state helpers' hdmi_validate_vrr
function in order to check and derive the state necessary for HDMI Quick
Media Switching (QMS) support.

Co-developed-by: Derek Foreman <derek.foreman at collabora.com>
Signed-off-by: Derek Foreman <derek.foreman at collabora.com>
Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli at collabora.com>
---
 drivers/gpu/drm/display/drm_hdmi_state_helper.c | 103 +++++++++++++++++++++++-
 1 file changed, 102 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index 7237070fc9ee..d392ae2908f9 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -2,6 +2,7 @@
 
 #include <linux/debugfs.h>
 #include <linux/export.h>
+#include <linux/gcd.h>
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_connector.h>
@@ -950,6 +951,26 @@ hdmi_generate_infoframes(const struct drm_connector *connector,
 	return 0;
 }
 
+static const struct {
+	u8 tfr_byte;
+	u32 rate_n;
+	u32 rate_d;
+} hdmi_qms_tfrs[] = {
+	{ 1, 24000, 1001 },
+	{ 2, 24, 1 },
+	{ 3, 25, 1 },
+	{ 4, 30000, 1001 },
+	{ 5, 30, 1 },
+	{ 6, 48000, 1001 },
+	{ 7, 48, 1 },
+	{ 8, 50, 1 },
+	{ 9, 60000, 1001 },
+	{ 10, 60, 1 },
+	{ 11, 100, 1 },
+	{ 12, 120000, 1001 },
+	{ 13, 120, 1 },
+};
+
 /**
  * cmp_fraction - compares two fractional numbers
  * @a: numerator of the first fraction
@@ -988,6 +1009,69 @@ static int cmp_fraction(u32 a, u32 b, u32 c, u32 d)
 	return 0;
 }
 
+/**
+ * hdmi_validate_qms - Validate HDMI QMS state
+ * @crtc_state: pointer to a &struct drm_crtc_state to run validation on
+ * @info: pointer to a &struct drm_display_info of the accompanying connector
+ *
+ * Validate that the drm_crtc_vrr_state.vrr_min_numerator and
+ * drm_crtc_vrr_state.vrr_min_denominator are acceptable for HDMI QMS, and check
+ * that the display is HDMI QMS capable.
+ *
+ * Returns:
+ *  - Negative errno on failure
+ *  - the corresponding QMS signaling byte for the target frame rate otherwise
+ */
+static int hdmi_validate_qms(struct drm_crtc_state *crtc_state,
+			     struct drm_connector_state *conn_state,
+			     const struct drm_display_info *info)
+{
+	u32 rate_n = crtc_state->vrr_state.vrr_min_n;
+	u32 rate_d = crtc_state->vrr_state.vrr_min_d;
+	u32 min_rate_n, max_rate;
+	u32 g, i;
+
+	if (!conn_state->hdmi.qms_enabled)
+		return 0;
+
+	if (!info->hdmi.qms_capable)
+		return -EOPNOTSUPP;
+
+	if (!drm_crtc_helper_vrr_is_fixed_rate(&crtc_state->vrr_state))
+		return -EINVAL;
+
+	if (info->hdmi.qms_tfr_min)
+		min_rate_n = 24000;
+	else
+		min_rate_n = info->monitor_range.min_vfreq * 1000;
+
+	if (info->hdmi.qms_tfr_max)
+		max_rate = info->monitor_range.max_vfreq;
+	else
+		max_rate = 60;
+
+	g = gcd(rate_n, rate_d);
+	if (g != 1) {
+		rate_n /= g;
+		rate_d /= g;
+	}
+
+	if (!rate_d)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(hdmi_qms_tfrs); i++) {
+		if (cmp_fraction(min_rate_n, 1001, hdmi_qms_tfrs[i].rate_n,
+				 hdmi_qms_tfrs[i].rate_d) > 0)
+			continue;
+		if (rate_n == hdmi_qms_tfrs[i].rate_n &&
+		    rate_d == hdmi_qms_tfrs[i].rate_d &&
+		    cmp_fraction(rate_n, rate_d, max_rate, 1) <= 0)
+			return hdmi_qms_tfrs[i].tfr_byte;
+	}
+
+	return -EINVAL;
+}
+
 static int hdmi_calculate_vtotal(const struct drm_display_mode *mode,
 				 u32 rate_n, u32 rate_d, u16 *out_vtotal,
 				 u32 *out_denom, u32 *out_frame_err)
@@ -1093,6 +1177,8 @@ static int hdmi_validate_vrr(struct drm_connector *connector,
 {
 	struct drm_connector_state *new_conn_state =
 		drm_atomic_get_new_connector_state(state, connector);
+	struct drm_connector_state *old_conn_state =
+		drm_atomic_get_old_connector_state(state, connector);
 	struct drm_crtc_state *new_crtc_state =
 		drm_atomic_get_new_crtc_state(state, new_conn_state->crtc);
 	struct drm_crtc_state *old_crtc_state =
@@ -1113,6 +1199,7 @@ static int hdmi_validate_vrr(struct drm_connector *connector,
 
 	/* Save on the expensive vic lookup, if nothing else. */
 	if (!new_crtc_state->mode_changed &&
+	    !new_crtc_state->connectors_changed &&
 	    old_crtc_state->vrr_enabled &&
 	    old_vrr_state->vrr_min_n == vrr_state->vrr_min_n &&
 	    old_vrr_state->vrr_min_d == vrr_state->vrr_min_d &&
@@ -1143,7 +1230,9 @@ static int hdmi_validate_vrr(struct drm_connector *connector,
 		max_vfreq_n = mode_refresh;
 
 	is_fixed = drm_crtc_helper_vrr_is_fixed_rate(vrr_state);
-	if (is_fixed && info->hdmi.cinema_vrr)
+	if (is_fixed && (info->hdmi.cinema_vrr || (info->hdmi.qms_tfr_min &&
+						   new_conn_state->hdmi.qms_enabled &&
+						   info->hdmi.qms_capable)))
 		min_vfreq_n = 24;
 
 	if (!min_vfreq_n) {
@@ -1165,6 +1254,18 @@ static int hdmi_validate_vrr(struct drm_connector *connector,
 		return ret;
 	}
 
+	ret = hdmi_validate_qms(new_crtc_state, new_conn_state, info);
+	if (ret < 0) {
+		drm_dbg_kms(dev, "Invalid QMS rate: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+
+	new_conn_state->hdmi.qms_tfr_byte = ret;
+	if (new_conn_state->hdmi.qms_tfr_byte != old_conn_state->hdmi.qms_tfr_byte)
+		vrr_state->dynamic = true;
+	else
+		vrr_state->dynamic = false;
+
 	if (!is_fixed) {
 		vrr_state->dynamic = true;
 

-- 
2.55.0