linux-kernel - Re: [PATCH v5] ARM64: dts: meson-gx: Add firmware reserved memory zones

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Message-ID: <eca803d3-1a67-cda5-554d-4313ae56635e@suse.de>
Date:   Thu, 19 Jan 2017 02:18:27 +0100
From:   Andreas Färber <afaerber@...e.de>
To:     Neil Armstrong <narmstrong@...libre.com>, xypron.glpk@....de,
        khilman@...libre.com, carlo@...one.org
Cc:     linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v5] ARM64: dts: meson-gx: Add firmware reserved memory
 zones

Am 19.01.2017 um 01:20 schrieb Andreas Färber:
> Hi,
> 
> Am 18.01.2017 um 17:50 schrieb Neil Armstrong:
>> The Amlogic Meson GXBB/GXL/GXM secure monitor uses part of the memory space,
>> this patch adds these reserved zones.
>>
>> Without such reserved memory zones, running the following stress command :
>> $ stress-ng --vm 16 --vm-bytes 128M --timeout 10s
>> multiple times:
>>
>> Could lead to the following kernel crashes :
>> [   46.937975] Bad mode in Error handler detected on CPU1, code 0xbf000000 -- SError
>> ...
>> [   47.058536] Internal error: Attempting to execute userspace memory: 8600000f [#3] PREEMPT SMP
>> ...
>> Instead of the OOM killer.
>>
> 
> I miss a Fixes: or Cc: here for the backport you desired. To have it
> fixed back to my very introduction:
> 
> Fixes: 4f24eda8401f ("ARM64: dts: Prepare configs for Amlogic Meson GXBaby")
> 
> People backporting it would need to handle the meson-{gx => gxbb}.dtsi
> transition for 4.9 down to 4.6, which seems fairly straightforward.
> 
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>> ---
>>  arch/arm64/boot/dts/amlogic/meson-gx.dtsi | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>
>> Changes since v4 at [5]:
>> - Move start of ddr memory to reserved-memory node
>> - Drop memory node move
>> - Fix typo in sizes
>>
>> Changes since resent v2 at [4]:
>> - Fix invalid comment of useable memory attributes
>>
>> Changes since original v2 at [3]:
>> - Typo in commit 2GiB -> 1GiB, 4GiB -> 2GiB
>>
>> Changes since v2 at [2]:
>> - Moved all memory node out of dtsi
>> - Added comment about useable memory
>> - Fixed comment about secmon reserved zone
>>
>> Changes since v1 at [1] :
>> - Renamed reg into linux,usable-memory to ovveride u-boot memory
>> - only kept secmon memory zone
>>
>> [1] http://lkml.kernel.org/r/20161212101801.28491-1-narmstrong@baylibre.com
>> [2] http://lkml.kernel.org/r/1483105232-6242-1-git-send-email-narmstrong@baylibre.com
>> [3] http://lkml.kernel.org/r/1484128128-22454-1-git-send-email-narmstrong@baylibre.com
>> [4] http://lkml.kernel.org/r/1484128540-22662-1-git-send-email-narmstrong@baylibre.com
>> [5] http://lkml.kernel.org/r/1484129414-23325-1-git-send-email-narmstrong@baylibre.com
>>
>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gx.dtsi b/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
>> index eada0b5..63d52b7 100644
>> --- a/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
>> +++ b/arch/arm64/boot/dts/amlogic/meson-gx.dtsi
>> @@ -55,6 +55,24 @@
>>  	#address-cells = <2>;
>>  	#size-cells = <2>;
>>  
>> +	reserved-memory {
>> +		#address-cells = <2>;
>> +		#size-cells = <2>;
>> +		ranges;
>> +
>> +		/* 16 MiB reserved for Hardware ROM Firmware */
>> +		hwrom: hwrom {
> 
> Both sub-nodes get a label that is unused, but reserved-memory itself
> does not (my v4 remark). Intentional?
> 
>> +			reg = <0x0 0x0 0x0 0x1000000>;
>> +			no-map;
>> +		};
>> +
>> +		/* 2 MiB reserved for ARM Trusted Firmware (BL31) */
>> +		secmon: secmon {
> 
> I note that this .dtsi further down has a node /firmware/secure-monitor
> with label sm.
> a) Is there any naming convention such as secmon_mem to adopt here to
> avoid mixups with sm?
> b) Should this secmon node be referenced in the secure-monitor node via
> memory-node = <&secmon>; to model their connection, thereby giving the
> label a use? Or should we maybe merge the two nodes by moving the
> compatible string here?
> 
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

Answering my own question: the example labels use _reserved suffix.

>> +			reg = <0x0 0x10000000 0x0 0x200000>;

And since we use a reg property here, the node name should get a unit
address to avoid future dtc warnings/errors. Ditto for hwrom.

>> +			no-map;
>> +		};
>> +	};
>> +
>>  	cpus {
>>  		#address-cells = <0x2>;
>>  		#size-cells = <0x0>;
> 
> Anyway, objection resolved,
> 
> Reviewed-by: Andreas Färber <afaerber@...e.de>
> 
> I don't expect breakage from these more confined additions, but I can
> try to test tomorrow.
> 
> Thanks,
> Andreas
> 


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