[PATCH v8 5/5] arm64: dts: qcom: msm8998: reserve potentially inaccessible clocks

[michael.srba@seznam.cz]

From: Michael Srba <michael.srba@seznam.cz>

With the gcc driver now being more complete and describing clocks which
might not always be write-accessible to the OS, conservatively specify
all such clocks as protected in the SoC dts.
The board dts - or even user-supplied dts - can override this property
to reflect the actual configuration.

Signed-off-by: Michael Srba <Michael.Srba@seznam.cz>
---
 CHANGES:
 - v2: add this patch
 - v3: fix missing Signed-off-by
 - v4: add a proper explanation as per review, (hopefully) fix the subject and commit message
 - v5: none
 - v6: none
 - v7: none
 - v8: none
---

 arch/arm64/boot/dts/qcom/msm8998.dtsi | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/msm8998.dtsi b/arch/arm64/boot/dts/qcom/msm8998.dtsi
index f273bc1ff629..16dccf9d881e 100644
--- a/arch/arm64/boot/dts/qcom/msm8998.dtsi
+++ b/arch/arm64/boot/dts/qcom/msm8998.dtsi
@@ -863,6 +863,21 @@ gcc: clock-controller@100000 {
 
 			clock-names = "xo", "sleep_clk";
 			clocks = <&xo>, <&sleep_clk>;
+
+			/*
+			 * The hypervisor typically configures the memory region where these clocks
+			 * reside as read-only for the HLOS. If the HLOS tried to enable or disable
+			 * these clocks on a device with such configuration (e.g. because they are
+			 * enabled but unused during boot-up), the device will most likely decide
+			 * to reboot.
+			 * In light of that, we are conservative here and we list all such clocks
+			 * as protected. The board dts (or a user-supplied dts) can override the
+			 * list of protected clocks if it differs from the norm, and it is in fact
+			 * desired for the HLOS to manage these clocks
+			 */
+			protected-clocks = <AGGRE2_SNOC_NORTH_AXI>,
+					   <SSC_XO>,
+					   <SSC_CNOC_AHBS_CLK>;
 		};
 
 		rpm_msg_ram: sram@778000 {
-- 
2.34.1