[PATCH 3/3] drm/omap: dsi: Ensure the device is active during probe

[Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>]

The probe function performs hardware access to read the number of
supported data lanes from a configuration register and thus requires the
device to be active. Ensure this by surrounding the access with
dsi_runtime_get() and dsi_runtime_put() calls.

Additionally we need to introduce a hack in the DSI runtime suspend and
resume callbacks, as they try to manage the runtime PM state of the
DISPC, which is not available at DSI probe time. The proper fix is to
move DISPC runtime PM handling to omapdrm completely, but it requires
more testing.

Fixes: edb715dffdee ("drm/omap: dss: dsi: Move initialization code from bind to probe")
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/omapdrm/dss/dsi.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
index 394c129cfb3b..c10dac9dfe4c 100644
--- a/drivers/gpu/drm/omapdrm/dss/dsi.c
+++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
@@ -5409,11 +5409,14 @@ static int dsi_probe(struct platform_device *pdev)
 
 	/* DSI on OMAP3 doesn't have register DSI_GNQ, set number
 	 * of data to 3 by default */
-	if (dsi->data->quirks & DSI_QUIRK_GNQ)
+	if (dsi->data->quirks & DSI_QUIRK_GNQ) {
+		dsi_runtime_get(dsi);
 		/* NB_DATA_LANES */
 		dsi->num_lanes_supported = 1 + REG_GET(dsi, DSI_GNQ, 11, 9);
-	else
+		dsi_runtime_put(dsi);
+	} else {
 		dsi->num_lanes_supported = 3;
+	}
 
 	r = dsi_init_output(dsi);
 	if (r)
@@ -5470,7 +5473,8 @@ static int dsi_runtime_suspend(struct device *dev)
 	/* wait for current handler to finish before turning the DSI off */
 	synchronize_irq(dsi->irq);
 
-	dispc_runtime_put(dsi->dss->dispc);
+	if (dsi->dss && dsi->dss->dispc)
+		dispc_runtime_put(dsi->dss->dispc);
 
 	return 0;
 }
@@ -5480,9 +5484,18 @@ static int dsi_runtime_resume(struct device *dev)
 	struct dsi_data *dsi = dev_get_drvdata(dev);
 	int r;
 
-	r = dispc_runtime_get(dsi->dss->dispc);
-	if (r)
-		return r;
+	/*
+	 * FIXME: The device is resumed from the probe function before the dss
+	 * is available, in order to read a hardware configuration register.
+	 * This doesn't require resuming the DISPC, so make it conditional. The
+	 * DISPC runtime PM handling should instead be controlled from omapdrm,
+	 * which is already partly the case, but needs additional testing.
+	 */
+	if (dsi->dss && dsi->dss->dispc) {
+		r = dispc_runtime_get(dsi->dss->dispc);
+		if (r)
+			return r;
+	}
 
 	dsi->is_enabled = true;
 	/* ensure the irq handler sees the is_enabled value */
-- 
Regards,

Laurent Pinchart