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arm64: dts: qcom: sdm845-oneplus-common: guard rmtfs-mem

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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>
This commit is contained in:
Caleb Connolly 2021-05-02 01:42:57 +00:00 committed by Bjorn Andersson
parent 5eabd602d2
commit e60fd5ac1f
1 changed files with 12 additions and 0 deletions
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12
arch/arm64/boot/dts/qcom/sdm845-oneplus-common.dtsi
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@ -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