Subject: Re: [PATCH] arm64: dts: renesas: Add /soc dma-ranges

From: Marek Vasut <[email-masked]>
Date: Mon, 9 Sep 2019 11:12:55 +0200

On 9/9/19 11:05 AM, Geert Uytterhoeven wrote:
> Hi Marek,

Hi,

> On Mon, Sep 9, 2019 at 10:42 AM Marek Vasut <[email-masked]> wrote:
>> On 9/9/19 10:19 AM, Geert Uytterhoeven wrote:
>>> On Sat, Sep 7, 2019 at 6:16 PM <[email-masked]> wrote:
>>>> From: Marek Vasut <[email-masked]>
>>>>
>>>> Add dma-ranges property into /soc node to describe the DMA capabilities
>>>> of the bus. This is currently needed to translate PCI DMA ranges, which
>>>> are limited to 32bit addresses.
>>>>
>>>> Signed-off-by: Marek Vasut <[email-masked]>
>>>
>>> Thanks for your patch!
>>>
>>>> NOTE: This is needed for the following patches to work correctly:
>>>>       https://patchwork.ozlabs.org/patch/1144870/
>>>>       https://patchwork.ozlabs.org/patch/1144871/
>>>
>>> What happens with the above patches applied, and without this one?
>>
>> It triggers https://patchwork.kernel.org/patch/11087391/#22811745
> 
> Sure. But what does that mean?
> PCI devices just not working?
> Random memory corruption?
> System lockup?
> Anything else?

Instead of translating the PCI DMA range to 0x40000000-0xffffffff , the
PCI code in the aforementioned patches defaults to maximum range, which
prevents various devices from working correctly, as the buffers get
allocated above the 32bit boundary.

>>> As PCI/OF driver patches go in through different trees, is it safe to apply
>>> this patch now?
>>> Should they go in together?
>>
>> I didn't get any feedback on the other two patches, but this one here is
>> safe to go in either way.
>>
>>>>  arch/arm64/boot/dts/renesas/r8a7795.dtsi  | 1 +
>>>>  arch/arm64/boot/dts/renesas/r8a7796.dtsi  | 1 +
>>>>  arch/arm64/boot/dts/renesas/r8a77965.dtsi | 1 +
>>>
>>> Do we need similar patches for the other R-Car Gen3 and RZ/G2 DTS files?
>>> What about R-Car Gen2 and RZ/G1?
>> I suspect we need such patches for any ARM64 machine with PCIe with this
>> 32bit limitation.
> 
> What about R-Car Gen2 and RZ/G1, which are ARM32, with LPAE?

Presumably we need that too ?

-- 
Best regards,
Marek Vasut

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