linux-kernel - Re: [PATCH v2 4/5] ALSA: emu10k1: make sure synth DMA pages are allocated with DMA functions

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Date:   Mon, 12 Feb 2018 23:14:50 +0100
From:   "Maciej S. Szmigiero" <mail@...iej.szmigiero.name>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/5] ALSA: emu10k1: make sure synth DMA pages are
 allocated with DMA functions

On 12.02.2018 13:44, Takashi Iwai wrote:
> On Sat, 27 Jan 2018 15:42:47 +0100,
>  Maciej S. Szmigiero  wrote:
>>
>> Commit a5003fc04113 ("[ALSA] emu10k1 - simplify page allocation for synth")
>> switched from using the DMA allocator for synth DMA pages to manually
>> calling alloc_page().
>> However, this usage has an implicit assumption that the DMA address space
>> for the emu10k1-family chip is the same as the CPU physical address space
>> which is not true for a system with a IOMMU.
>>
>> Since this made the synth part of the driver non-functional on such systems
>> let's effectively revert that commit.
> 
> Let's keep (or re-add after this revert) the simplification with
> __synth_free_pages().  Other than that I have no objection to this
> change.

Will keep the simplification via __synth_free_pages() function in a respin.

> thanks,
> 
> Takashi

Thanks,
Maciej