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Date: Thu, 9 May 2024 17:16:13 +0200
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Subject: Re: [PATCH] dma: fix DMA sync for drivers not calling dma_set_mask*()
To: Steven Price <steven.price@arm.com>, Christoph Hellwig <hch@lst.de>
CC: Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>,
	Marek Szyprowski <m.szyprowski@samsung.com>, Robin Murphy
	<robin.murphy@arm.com>, Joerg Roedel <joro@8bytes.org>, Will Deacon
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References: <20240509144616.938519-1-aleksander.lobakin@intel.com>
 <ce83b3b8-2246-4006-a111-f2da0740bd8e@arm.com>
From: Alexander Lobakin <aleksander.lobakin@intel.com>
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From: Steven Price <steven.price@arm.com>
Date: Thu, 9 May 2024 16:11:26 +0100

> On 09/05/2024 15:46, Alexander Lobakin wrote:
>> There are several reports that the DMA sync shortcut broke non-coherent
>> devices.
>> dev->dma_need_sync is false after the &device allocation and if a driver
>> didn't call dma_set_mask*(), it will still be false even if the device
>> is not DMA-coherent and thus needs synchronizing. Due to historical
>> reasons, there's still a lot of drivers not calling it.
>> Invert the boolean, so that the sync will be performed by default and
>> the shortcut will be enabled only when calling dma_set_mask*().
>>
>> Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> Closes: https://lore.kernel.org/lkml/46160534-5003-4809-a408-6b3a3f4921e9@samsung.com
>> Reported-by: Steven Price <steven.price@arm.com>
>> Closes: https://lore.kernel.org/lkml/010686f5-3049-46a1-8230-7752a1b433ff@arm.com
>> Fixes: 32ba8b823252 ("dma: avoid redundant calls for sync operations")
>> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
> 
> Tested-by: Steven Price <steven.price@arm.com>

Thank!

> 
> Thanks for the quick fix.
> 
> Note that the fixes hash (32ba8b823252) is not the one in linux-next -
> that's f406c8e4b770. If the branch is getting rebased then no problem, I
> just thought I should point that out.

Oh crap, it really should be f406. Wrong tree again >_<

Chris, would you fix it when applying or I should resend?

> 
> Thanks,
> Steve

Thanks,
Olek