[PATCH v6 2/2] arm64: dts: qcom: sdm845-db845c: Mark cont splash memory region as reserved

[Amit Pundir]

Adding a reserved memory region for the framebuffer memory
(the splash memory region set up by the bootloader).

It fixes a kernel panic (arm-smmu: Unhandled context fault
at this particular memory region) reported on DB845c running
v5.10.y.

Cc: stable at vger.kernel.org # v5.10+
Reviewed-by: Caleb Connolly <caleb.connolly at linaro.org>
Signed-off-by: Amit Pundir <amit.pundir at linaro.org>
---
v6: Collected review tag, updated commit message for the
    context and marked for stable kernel versions.

v5: Re-sending with updated dt-bindings patch in mdss-common
    schema.

v4: Re-sending this along with a new dt-bindings patch to
    document memory-region property in qcom,sdm845-mdss
    schema and keep dtbs_check happy.

v3: Point this reserved region to MDSS.

v2: Updated commit message.

There was some dicussion on v1 but it didn't go anywhere,
https://lore.kernel.org/linux-kernel/20230124182857.1524912-1-amit.pundir@linaro.org/T/#u.
The general consensus is that this memory should be freed and be
made resuable but that (releasing this piece of memory) has been
tried before and it is not trivial to return the reserved memory
node to the system RAM pool in this case.

 arch/arm64/boot/dts/qcom/sdm845-db845c.dts | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
index d6b464cb61d6..f546f6f57c1e 100644
--- a/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
+++ b/arch/arm64/boot/dts/qcom/sdm845-db845c.dts
@@ -101,6 +101,14 @@ hdmi_con: endpoint {
 		};
 	};
 
+	reserved-memory {
+		/* Cont splash region set up by the bootloader */
+		cont_splash_mem: framebuffer at 9d400000 {
+			reg = <0x0 0x9d400000 0x0 0x2400000>;
+			no-map;
+		};
+	};
+
 	lt9611_1v8: lt9611-vdd18-regulator {
 		compatible = "regulator-fixed";
 		regulator-name = "LT9611_1V8";
@@ -506,6 +514,7 @@ &i2c14 {
 };
 
 &mdss {
+	memory-region = <&cont_splash_mem>;
 	status = "okay";
 };
 
-- 
2.25.1