[PATCH v6 11/18] drm/bridge: inno-hdmi: Add .mode_valid platform operation

[Michal Wilczynski]

inno_hdmi_bridge_mode_valid() validates the pixel clock against
hdmi->refclk, but that clock is optional and is only present on
platforms that describe a "ref" clock. Platforms where the pixel clock
is produced by a separate device - such as the StarFive JH7110, whose
PHY is both the clock and the PHY provider - have no "ref" clock, so
the check is skipped entirely and every mode is reported as valid.

A mode the platform cannot generate is then advertised to userspace.
The subsequent modeset appears to succeed, since the atomic enable path
cannot fail, and the display silently stays blank.

Add a .mode_valid platform operation so platforms can reject modes they
are unable to drive. Platforms that do not implement it are unaffected.

Reviewed-by: Joshua Peisach <jpeisach at ubuntu.com>
Tested-by: Byron Stanoszek <gandalf at winds.org>
Tested-by: OOHehir <oo.hehir at gmail.com>
Signed-off-by: Michal Wilczynski <m.wilczynski at samsung.com>
---
 drivers/gpu/drm/bridge/inno-hdmi.c | 9 +++++++++
 include/drm/bridge/inno_hdmi.h     | 5 ++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/inno-hdmi.c b/drivers/gpu/drm/bridge/inno-hdmi.c
index 708d4c03f8880429f99680abd0c92e150312237b..2684a3cc5667ce133357dccb8d214806db27f863 100644
--- a/drivers/gpu/drm/bridge/inno-hdmi.c
+++ b/drivers/gpu/drm/bridge/inno-hdmi.c
@@ -823,6 +823,7 @@ static enum drm_mode_status inno_hdmi_bridge_mode_valid(struct drm_bridge *bridg
 							const struct drm_display_mode *mode)
 {
 	struct inno_hdmi *hdmi = bridge_to_inno_hdmi(bridge);
+	const struct inno_hdmi_plat_ops *plat_ops = hdmi->plat_data->ops;
 	unsigned long mpixelclk, max_tolerance;
 	long rounded_refclk;
 
@@ -838,6 +839,14 @@ static enum drm_mode_status inno_hdmi_bridge_mode_valid(struct drm_bridge *bridg
 	if (inno_hdmi_find_phy_config(hdmi, mpixelclk) < 0)
 		return MODE_CLOCK_HIGH;
 
+	if (plat_ops && plat_ops->mode_valid) {
+		enum drm_mode_status status;
+
+		status = plat_ops->mode_valid(hdmi->dev, mode);
+		if (status != MODE_OK)
+			return status;
+	}
+
 	if (hdmi->refclk) {
 		rounded_refclk = clk_round_rate(hdmi->refclk, mpixelclk);
 		if (rounded_refclk < 0)
diff --git a/include/drm/bridge/inno_hdmi.h b/include/drm/bridge/inno_hdmi.h
index 0864f0d8862a4325821a84db6d04f14011d9aa78..790633fcea97a6b9840da7b19a0c0b0d7271fb83 100644
--- a/include/drm/bridge/inno_hdmi.h
+++ b/include/drm/bridge/inno_hdmi.h
@@ -8,15 +8,18 @@
 
 #include <linux/types.h>
 
+#include <drm/drm_modes.h>
+
 struct device;
 struct drm_encoder;
-struct drm_display_mode;
 struct inno_hdmi;
 struct platform_device;
 
 struct inno_hdmi_plat_ops {
 	void (*enable)(struct device *pdev, struct drm_display_mode *mode);
 	void (*disable)(struct device *pdev);
+	enum drm_mode_status (*mode_valid)(struct device *pdev,
+					   const struct drm_display_mode *mode);
 };
 
 struct inno_hdmi_phy_config {

-- 
2.34.1