[PATCH v3 0/4] Improve VCHIQ cache line size handling

Florian Fainelli f.fainelli at gmail.com
Mon Sep 17 10:51:56 PDT 2018


On 09/17/2018 04:47 AM, Phil Elwell wrote:
> Hi Stefan,
> 
> On 17/09/2018 12:39, Stefan Wahren wrote:
>> Hi Phil,
>>
>> Am 17.09.2018 um 10:22 schrieb Phil Elwell:
>>> Both sides of the VCHIQ communications mechanism need to agree on the cache
>>> line size. Using an incorrect value can lead to data corruption, but having the
>>> two sides using different values is usually worse.
>>>
>>> In the absence of an obvious convenient run-time method to determine the
>>> correct value in the ARCH=arm world, the downstream Raspberry Pi trees used a
>>> Device Tree property, written by the firmware, to configure the kernel driver.
>>> This method was vetoed during the upstreaming process, so a fixed value of 32
>>> was used instead, and some corruptions ensued. This is take 2 at arriving at
>>> the correct value.
>>>
>>> Add a new compatible string - "brcm,bcm2836-vchiq" - to indicate an SoC with
>>> a 64-byte cache line. Document the new string in the binding, and use it on
>>> the appropriate platforms.
>>>
>>> The final patch is a (seemingly cosmetic) correction of the Device Tree "reg"
>>> declaration for the device node, but it doubles as an indication to the
>>> Raspberry Pi firmware that the kernel driver is running a recent kernel driver
>>> that chooses the correct value. As such it would help if the DT patches are
>>> not merged before the driver patch.
>>>
>>> v3: Builds without errors, tested on multiple Raspberry Pi models.
>>> v2: Replaced ARM-specific logic used to determine cache line size with
>>>     a new compatible string for BCM2836 and BCM2837.
>>>
>>> Phil Elwell (4):
>>>   staging/vc04_services: Use correct cache line size
>>>   dt-bindings: soc: Document "brcm,bcm2836-vchiq"
>>>   ARM: dts: bcm283x: Correct vchiq compatible string
>>>   ARM: dts: bcm283x: Correct mailbox register sizes
>>
>> since my pull requests are out, would it be okay to apply patch #1 for
>> 4.20 and the DT stuff for 4.21 (with the assumption Rob is okay with
>> these patches)?
> 
> Patch 4 is the only one I'd like to be delayed, but delaying 2-4 is fine with me.

Humm, did you mean you would like not to be delayed? In any case Stefan,
you can send an additional pull request, and I will merge it and send a
second pull request towards ARM SoC maintainers, that's not a problem.
-- 
Florian



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