drm/msm/dsi: implement opp table based check for dsi_mgr_bridge_mode_valid()

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 v3:
	- make the comment shorter
	- handle all errors except ENODEV

Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/15
Reported-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/518008/
Link: https://lore.kernel.org/r/20230112001600.12791-2-quic_abhinavk@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
index 3a1417397283..b20fddb534a7 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
@@ -450,6 +450,25 @@ 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);
+
+	/*
+	 * fail all errors except -ENODEV as that could mean that opp
+	 * table is not yet implemented
+	 */
+	opp = dev_pm_opp_find_freq_ceil(&pdev->dev, &byte_clk_rate);
+	if (IS_ERR(opp)) {
+		if (PTR_ERR(opp) == -ERANGE)
+			return MODE_CLOCK_RANGE;
+		else if (PTR_ERR(opp) != -ENODEV)
+			return MODE_ERROR;
+	} else {
+		dev_pm_opp_put(opp);
+	}
 
 	return msm_dsi_host_check_dsc(host, mode);
 }