linux-kernel - Re: [RFC] mmc: meson-gx: use memcpy

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Date:   Wed, 9 Jun 2021 16:01:13 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Neil Armstrong <narmstrong@...libre.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        ulf.hansson@...aro.org
Cc:     khilman@...libre.com, jbrunet@...libre.com,
        martin.blumenstingl@...glemail.com, linux-mmc@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [RFC] mmc: meson-gx: use memcpy_to/fromio for dram-access-quirk

On 2021-06-09 15:55, Neil Armstrong wrote:
> Hi Robin,
> 
> On 09/06/2021 16:45, Robin Murphy wrote:
>> On 2021-06-09 14:07, Neil Armstrong wrote:
>>> Hi,
>>>
>>> On 08/06/2021 17:50, Marek Szyprowski wrote:
>>>> Hi
>>>>
>>>> On 08.06.2021 17:33, Neil Armstrong wrote:
>>>>> It has been reported that usage of memcpy() to/from an iomem mapping is invalid,
>>>>> and and recent arm64 memcpy update [1] triggers a memory abort when dram-access-quirk
>>>>> is used on the G12A/G12B platforms.
>>>>>
>>>>> This adds a local sg_copy_to_buffer which makes usage of io versions of memcpy
>>>>> when dram-access-quirk is enabled.
>>>>>
>>>>> Fixes: acdc8e71d9bb ("mmc: meson-gx: add dram-access-quirk")
>>>>> Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>>>> Suggested-by: Mark Rutland <mark.rutland@....com>
>>>>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>>>>>
>>>>> [1] 285133040e6c ("arm64: Import latest memcpy()/memmove() implementation")
>>>>>
>>>>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
>>>>> ---
>>>>> Hi Ulf, Marek, Mark,
>>>>>
>>>>> I haven't tested the patch yet, but should fix issue reported at [2].
>>>>
>>>> Works fine here and fixed the issue.
>>>>
>>>> Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>
>>>
>>> Thanks, I'll need to rework to pass an __iomem pointer to memcpy_to/fromio so sparse doesn't scream anymore.
>>
>> Hmm, might it be worth factoring out general sg_copy_{to,from}_iomem() helpers? From a quick grep I found at least mv_cesa_sg_copy() already doing essentially the same thing as meson_mmc_copy_buffer().
> 
> It's definitely worth it, but since we need a quick fix, we should have meson_mmc_copy_buffer() as a fix then we should definitely move to sg_copy_{to,from}_iomem() helpers

Oh, that makes sense for sure - I was just doing some general thinking 
out loud before I forget about the whole thing :)

Cheers,
Robin.