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From: Greg KH <gregkh@linuxfoundation.org>
To: Gavin Li <gavinli@thegavinli.com>
Cc: linux-usb@vger.kernel.org, Gavin Li <git@thegavinli.com>
Subject: Re: [PATCH] usb: devio: fix mmap() on non-coherent DMA architectures
Date: Mon, 5 Aug 2019 17:17:13 +0200	[thread overview]
Message-ID: <20190805151713.GA7067@kroah.com> (raw)
In-Reply-To: <CA+GxvY7LswVFZvk0mLRLgUqdo=Gb0pQ1KMsgmWbiFEPvMvquXQ@mail.gmail.com>

On Fri, Aug 02, 2019 at 10:57:00AM -0700, Gavin Li wrote:
> usbfs mmap() looks like it was introduced for 4.6 in commit
> f7d34b445abc, so it should probably be backported to 4.9 and onwards.
> This issue has been present since the introduction of the feature.
> 
> One sidenote: this patch will cause the following warning on x86 due
> to dmap_mmap_coherent() trying to map normal memory in as uncached:
> 
> x86/PAT: ... map pfn RAM range req uncached-minus for [mem
> 0x77b000000-0x77b210fff], got write-back
> 
> This warning is harmless, as x86 is DMA coherent and the memory gets
> correctly mapped in as write-back. I will submit a patch to the DMA
> mapping team to eliminate this warning.

Let me know what the git commit id of that patch is, I will wait for it
to hit the tree before adding this one.

thanks,

greg k-h

  reply	other threads:[~2019-08-05 15:17 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01 22:04 [PATCH] usb: devio: fix mmap() on non-coherent DMA architectures gavinli
2019-08-02 12:14 ` Greg KH
2019-08-02 17:57   ` Gavin Li
2019-08-05 15:17     ` Greg KH [this message]
2019-09-04  7:05       ` Greg KH
  -- strict thread matches above, loose matches on Subject: below --
2019-08-01 22:01 gavinli
2019-08-05 11:37 ` David Laight
2019-08-05 18:33   ` Gavin Li

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