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From: Michael Schmitz <schmitzmic@gmail.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Christoph Hellwig <hch@lst.de>,
	Finn Thain <fthain@telegraphics.com.au>,
	"David S. Miller" <davem@davemloft.net>,
	linux-m68k <linux-m68k@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net] macmace: Set platform device coherent_dma_mask
Date: Fri, 4 May 2018 20:16:58 +1200	[thread overview]
Message-ID: <bf7667f7-a11f-87ac-3aca-130cca86d328@gmail.com> (raw)
In-Reply-To: <CAMuHMdW+waQSQxLvBXEZkhCAj_kh=4SR1hZ4FAeC8YWXtRKg1A@mail.gmail.com>

Hi Geert,

Am 04.05.2018 um 19:24 schrieb Geert Uytterhoeven:
> Hi Michael,
> 
>>> Yes, that would be useful.  The other assumption could be that
>>> platform devices always allow an all-0xff dma mask.
>>
>> That's not always true (Atari NCR5380 SCSI and floppy would use a 24
>> bit DMA mask). We use bounce buffers allocated from a dedicated lowmem
>> pool there currently, and for all I know don't use the DMA API yet.
>>
>> I bet that is a rare exception though. Setting the default DMA mask
>> for platform devices to all-0xff and letting the few odd drivers force
>> a different setting seems the best way forward.
> 
> I'd say that's usually a property of the platform, not of the device?

Right - I was thinking 'm68k' as platform, not a particular machine like
Mac or Falcon (the 24 bit mask only applies to that particular model
anyway).

> So IMHO it belongs in the platform code, not in the device driver code.

OK - let's have a default mask of 64 bit, and allow machine specific
platform_init() to override using a new helper function.

Cheers,

	Michael

> Gr{oetje,eeting}s,
> 
>                         Geert
> 

  reply	other threads:[~2018-05-04  8:17 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <S1751632AbeECEYA/20180503042400Z+254@vger.kernel.org>
2018-05-03  7:25 ` Geert Uytterhoeven
2018-05-03  8:38   ` Finn Thain
2018-05-03  8:46     ` Geert Uytterhoeven
2018-05-03  8:51       ` Christoph Hellwig
2018-05-03 20:24         ` Michael Schmitz
2018-05-04  7:24           ` Geert Uytterhoeven
2018-05-04  8:16             ` Michael Schmitz [this message]
2018-05-10  1:25         ` Finn Thain
2018-05-10  1:25       ` Finn Thain
2018-05-10 20:27         ` Michael Schmitz
2018-05-10 23:55           ` Finn Thain
2018-05-11  2:11             ` Michael Schmitz
2018-05-11  3:28               ` Finn Thain
2018-05-11  4:18                 ` Michael Schmitz
2018-05-11  5:28                   ` Finn Thain
2018-05-11  9:30                     ` Michael Schmitz
2018-05-11 10:06                       ` Finn Thain
2018-05-11 22:02                         ` Michael Schmitz
2018-05-03  4:23 Finn Thain

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