[PATCH 5.13 290/351] arm64: dts: qcom: sdm845-oneplus-common: guard rmtfs-mem

Greg Kroah-Hartman
2021-07-19T17:51:12Z

From: Caleb Connolly <caleb@connolly.tech>

[ Upstream commit e60fd5ac1f6851be5b2c042b39584bfcf8a66f57 ]

The rmtfs_mem region is a weird one, downstream allocates it
dynamically, and supports a "qcom,guard-memory" property which when set
will reserve 4k above and below the rmtfs memory.

A common from qcom 4.9 kernel msm_sharedmem driver:

/*
* If guard_memory is set, then the shared memory region
* will be guarded by SZ_4K at the start and at the end.
* This is needed to overcome the XPU limitation on few
* MSM HW, so as to make this memory not contiguous with
* other allocations that may possibly happen from other
* clients in the system.
*/

When the kernel tries to touch memory that is too close the
rmtfs region it may cause an XPU violation. Such is the case on the
OnePlus 6 where random crashes would occur usually after boot.

Reserve 4k above and below the rmtfs_mem to avoid hitting these XPU
Violations.

This doesn't entirely solve the random crashes on the OnePlus 6/6T but
it does seem to prevent the ones which happen shortly after modem
bringup.

Fixes: 288ef8a42612 ("arm64: dts: sdm845: add oneplus6/6t devices")
Signed-off-by: Caleb Connolly <caleb@connolly.tech>
Link: https://lore.kernel.org/r/20210502014146.85642-4-caleb@connolly.tech
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/boot/dts/qcom/sdm845-oneplus-common.dtsi | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/arch/arm64/boot/dts/qcom/sdm845-oneplus-common.dtsi b/arch/arm64/boot/dts/qcom/sdm845-oneplus-common.dtsi
index 8f617f7b6d34..f712771df0c7 100644
--- a/arch/arm64/boot/dts/qcom/sdm845-oneplus-common.dtsi
+++ b/arch/arm64/boot/dts/qcom/sdm845-oneplus-common.dtsi
@@ -46,6 +46,14 @@
};

reserved-memory {
+ /* The rmtfs_mem needs to be guarded due to "XPU limitations"
+ * it is otherwise possible for an allocation adjacent to the
+ * rmtfs_mem region to trigger an XPU violation, causing a crash.
+ */
+ rmtfs_lower_guard: memory@f5b00000 {
+ no-map;
+ reg = <0 0xf5b00000 0 0x1000>;
+ };
/*
* The rmtfs memory region in downstream is 'dynamically allocated'
* but given the same address every time. Hard code it as this address is
@@ -59,6 +67,10 @@
qcom,client-id = <1>;
qcom,vmid = <15>;
};
+ rmtfs_upper_guard: memory@f5d01000 {
+ no-map;
+ reg = <0 0xf5d01000 0 0x2000>;
+ };

/*
* It seems like reserving the old rmtfs_mem region is also needed to prevent
--
2.30.2