[PATCH 2/2] drm/msm/dsi: implement opp table based check for dsi_mgr_bridge_mode_valid()

[Abhinav Kumar]

Currently there is no protection against a user trying to set
an unsupported mode on DSI. Implement a check based on the opp
table whether the byte clock for the mode can be supported by
validating whether an opp table entry exists.

For devices which have not added opp table support yet, skip
this check otherwise it will break bootup on those devices.

changes in v2:
	- drop dev_pm_opp_get_opp_table() usage

Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/15
Reported-by: Rob Clark <robdclark at gmail.com>
Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
---
 drivers/gpu/drm/msm/dsi/dsi_manager.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
index 3a1417397283..c4c24dabfd6f 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
@@ -450,6 +450,31 @@ static enum drm_mode_status dsi_mgr_bridge_mode_valid(struct drm_bridge *bridge,
 	int id = dsi_mgr_bridge_get_id(bridge);
 	struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
 	struct mipi_dsi_host *host = msm_dsi->host;
+	struct platform_device *pdev = msm_dsi->pdev;
+	struct dev_pm_opp *opp;
+	unsigned long byte_clk_rate;
+
+	byte_clk_rate = dsi_byte_clk_get_rate(host, IS_BONDED_DSI(), mode);
+
+	/*
+	 * If dev_pm_opp_find_freq_ceil() returns -EINVAL, its a bad
+	 * pointer being passed, so treat as an error and return MODE_ERROR
+	 *
+	 * If dev_pm_opp_find_freq_ceil() returns -ERANGE, no clock
+	 * was found matching the byte_clk, so return MODE_CLOCK_RANGE
+	 *
+	 * If dev_pm_opp_find_freq_ceil() returns -ENODEV, don't treat
+	 * it as an error as it could mean opp table is not implemented
+	 */
+	opp = dev_pm_opp_find_freq_ceil(&pdev->dev, &byte_clk_rate);
+	if (IS_ERR(opp)) {
+		if (PTR_ERR(opp) == -EINVAL)
+			return MODE_ERROR;
+		else if (PTR_ERR(opp) == -ERANGE)
+			return MODE_CLOCK_RANGE;
+	} else {
+		dev_pm_opp_put(opp);
+	}
 
 	return msm_dsi_host_check_dsc(host, mode);
 }
-- 
2.39.0