Re: [PATCH v2] ARM: l2c: Add support for the "arm, shared-override" property

[Hauke Mehrtens <hauke@hauke-m.de>]

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On 06/02/2015 09:20 AM, Michal Simek wrote:
> On 05/15/2015 03:55 PM, Catalin Marinas wrote:
>> On Fri, May 15, 2015 at 11:10:28AM +0100, Russell King - ARM
>> Linux wrote:
>>> On Thu, May 07, 2015 at 05:02:57PM +0100, Catalin Marinas
>>> wrote:
>>>> On Thu, May 07, 2015 at 11:27:11AM +0200, Geert Uytterhoeven
>>>> wrote:
>>>>> diff --git a/Documentation/devicetree/bindings/arm/l2cc.txt
>>>>> b/Documentation/devicetree/bindings/arm/l2cc.txt index
>>>>> 0dbabe9a6b0abb91..2484aed78c86546d 100644 ---
>>>>> a/Documentation/devicetree/bindings/arm/l2cc.txt +++
>>>>> b/Documentation/devicetree/bindings/arm/l2cc.txt @@ -67,6
>>>>> +67,12 @@ Optional properties: disable if zero. -
>>>>> arm,prefetch-offset : Override prefetch offset value. Valid
>>>>> values are 0-7, 15, 23, and 31. +- arm,shared-override :
>>>>> The default behavior of the pl310 cache controller with +
>>>>> respect to the shareable attribute is to transform "normal
>>>>> memory +  non-cacheable transactions" into "cacheable no
>>>>> allocate" (for reads) or +  "write through no write
>>>>> allocate" (for writes). +  On systems where this may cause
>>>>> DMA buffer corruption, this property must be +  specified
>>>>> to indicate that such transforms are precluded.
>>>>> 
>>>>> Example:
>>>>> 
>>>>> diff --git a/arch/arm/mm/cache-l2x0.c
>>>>> b/arch/arm/mm/cache-l2x0.c index
>>>>> e309c8f35af5af61..86d0e7461e5b0b18 100644 ---
>>>>> a/arch/arm/mm/cache-l2x0.c +++ b/arch/arm/mm/cache-l2x0.c 
>>>>> @@ -1149,6 +1149,11 @@ static void __init
>>>>> l2c310_of_parse(const struct device_node *np, } }
>>>>> 
>>>>> +	if (of_property_read_bool(np, "arm,shared-override")) { +
>>>>> *aux_val |= L2C_AUX_CTRL_SHARED_OVERRIDE; +		*aux_mask &>>>>> ~L2C_AUX_CTRL_SHARED_OVERRIDE; +	} + prefetch >>>>> l2x0_saved_regs.prefetch_ctrl;
>>>>> 
>>>>> ret = of_property_read_u32(np, "arm,double-linefill",
>>>>> &val);
>>>> 
>>>> It looks fine to me.
>>>> 
>>>> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
>>>> 
>>>> (even better if a subsequent patch adds this property to all
>>>> the dts files containing "arm,pl310" ;))
>>> 
>>> Even better would be for the boot loader/firmware to set the
>>> bit.
>> 
>> In an ideal world, I agree. But, arguably, we already set other
>> bits in the PL310 AUXCTRL register (and related cache
>> controllers, just look at the l2cc.txt bindings).
>> 
>> If you want to rely on firmware, can we at least check this bit
>> and print a warning? Or go a step further and refuse to enable
>> PL310 when this bit is clear? Otherwise coherent (non-cacheable)
>> DMA operations are not safe.
>> 
> 
> Any update on this one? I have the patch for Zynq pending and I
> want to have any resolution on this in this generic way or simply
> by enabling it via aux_mask as is here. 
> https://lkml.org/lkml/2015/5/12/51 This patch can be reverted when
> this generic solution reach mainline.
> 
> Thanks, Michal

I do not see this in linux-next, and would like to use this.

Geert have you submitted this through this patch submission page?
http://www.arm.linux.org.uk/developer/patches/

Hauke

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