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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Michael Ellerman <mpe@ellerman.id.au>,
	Russell King - ARM Linux admin <linux@armlinux.org.uk>,
	Christian Zigotzky <chzigotzky@xenosoft.de>,
	Paul Mackerras <paulus@samba.org>
Cc: ulf.hansson@linaro.org, "R.T.Dickinson" <rtd2@xtra.co.nz>,
	linux-mmc@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
	"contact@a-eon.com" <contact@a-eon.com>,
	mad skateman <madskateman@gmail.com>,
	linuxppc-dev@lists.ozlabs.org,
	Christian Zigotzky <info@xenosoft.de>
Subject: Re: Onboard SD card doesn't work anymore after the 'mmc-v5.4-2' updates
Date: Wed, 23 Oct 2019 17:41:24 +1100	[thread overview]
Message-ID: <31d58f086f964937b27209bc18b334d9c9791767.camel@kernel.crashing.org> (raw)
In-Reply-To: <87muds586t.fsf@mpe.ellerman.id.au>

On Wed, 2019-10-23 at 16:42 +1100, Michael Ellerman wrote:
> 
> Right, it seems of_dma_is_coherent() has baked in the assumption that
> devices are non-coherent unless explicitly marked as coherent.
> 
> Which is wrong on all or at least most existing powerpc systems
> according to Ben.

This is probably broken on sparc(64) as well and whatever else uses
DT and is an intrinsicly coherent architecture (did we ever have
DT enabled x86s ? Wasn't OLPC such a beast ?).

I think this should have been done the other way around and default to
coherent since most traditional OF platforms are coherent, and you
can't just require those DTs to change.

> > Any ideas from the PPC maintainers?
> 
> Fixing it at the source seems like the best option to prevent future
> breakage.
> 
> So I guess that would mean making of_dma_is_coherent() return true/false
> based on CONFIG_NOT_COHERENT_CACHE on powerpc.
> 
> We could do it like below, which would still allow the dma-coherent
> property to work if it ever makes sense on a future powerpc platform.
> 
> I don't really know any of this embedded stuff well, so happy to take
> other suggestions on how to handle this mess.


  reply	other threads:[~2019-10-23  6:44 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <7b549219-a2e1-08c7-331b-9c3e4fdb8a8f@xenosoft.de>
     [not found] ` <3aeae0d8-e9be-2585-cbbd-70263cb495f1@xenosoft.de>
     [not found]   ` <20191015125105.GU25745@shell.armlinux.org.uk>
     [not found]     ` <5611f3bc-68aa-78ec-182a-1cb414202314@xenosoft.de>
     [not found]       ` <20191015131750.GV25745@shell.armlinux.org.uk>
2019-10-23  5:42         ` Onboard SD card doesn't work anymore after the 'mmc-v5.4-2' updates Michael Ellerman
2019-10-23  6:41           ` Benjamin Herrenschmidt [this message]
2019-10-23 13:52             ` Rob Herring
2019-10-23 14:12               ` Russell King - ARM Linux admin
2019-10-23 14:31               ` Russell King - ARM Linux admin
2019-10-25 22:28                 ` Rob Herring
2019-10-26  6:39                   ` Christoph Hellwig
2019-10-28  8:47                     ` Benjamin Herrenschmidt
2019-10-28  8:45                   ` Benjamin Herrenschmidt
2019-10-23 14:20           ` Christian Zigotzky
2019-11-04 14:44             ` Christian Zigotzky
2019-11-05  7:50               ` Bug 205201 - overflow of DMA mask and bus mask Christian Zigotzky

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