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From: "Marek Behún" <kabel@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Marcin Wojtas <mw@semihalf.com>,
	"Russell King (Oracle)" <linux@armlinux.org.uk>,
	pali@kernel.org, Robin Murphy <robin.murphy@arm.com>,
	Arnd Bergmann <arnd@kernel.org>,
	Andre Przywara <andre.przywara@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Lunn <andrew@lunn.ch>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	iommu@lists.linux-foundation.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: mvebu: select OF_DMA_DEFAULT_COHERENT if MACH_MVEBU_V7
Date: Tue, 4 Oct 2022 14:54:34 +0200	[thread overview]
Message-ID: <20221004145434.74bb0413@thinkpad> (raw)
In-Reply-To: <20221004083010.GA2312@lst.de>

On Tue, 4 Oct 2022 10:30:10 +0200
Christoph Hellwig <hch@lst.de> wrote:

> On Tue, Oct 04, 2022 at 10:17:23AM +0200, Marek Behún wrote:
> > Commit ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
> > caused a regression on the mvebu platform, wherein devices that are
> > dma-coherent are marked as dma-noncoherent, because although
> > mvebu_hwcc_notifier() after that commit still marks then as coherent,
> > the arm_coherent_dma_ops() function, which is called later, overwrites
> > this setting, since it is being called from drivers/of/device.c with
> > coherency parameter determined by of_dma_is_coherent(), and the
> > device-trees do not declare the 'dma-coherent' property.
> > 
> > Fix this by defaulting to dma-coherent for this platform in the
> > of_dma_is_coherent() function, if neither dma-coherent nor
> > dma-noncoherent is declared.  
> 
> Can't mvebu be part of multi-platform builds that would be broken by
> this change?

OK, if selecting that isn't possible, then my opinion is that this
should be handled by OF drivers. There is a precedent for this,
drivers/of/address.c has function of_empty_ranges_quirk().

So maybe something like
  of_dma_coherency_quirk(),
which will be called from of_dma_is_coherent() ?

> Also if we do this, shouldn't we also remove the notifier that set
> ->dma_coherent? 

Yes, the notifier should go away, IMO.

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  reply	other threads:[~2022-10-04 12:56 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-30 13:10 REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally" Marek Behún
2022-09-30 13:46 ` Robin Murphy
2022-09-30 14:52   ` Marek Behún
2022-09-30 15:02     ` Marek Behún
2022-09-30 16:41       ` Robin Murphy
2022-09-30 18:02         ` Marek Behún
2022-10-03  7:21           ` Christoph Hellwig
2022-10-03  7:30       ` Christoph Hellwig
2022-10-03 14:11         ` Russell King (Oracle)
2022-10-03 15:25           ` Marek Behún
2022-10-03 16:09             ` Pali Rohár
2022-10-03 19:04               ` Marek Behún
2022-10-03 19:08                 ` Pali Rohár
2022-10-03 21:30             ` Marcin Wojtas
2022-10-03 21:35               ` Pali Rohár
2022-10-03 22:03                 ` Marcin Wojtas
2022-10-04  7:10               ` Christoph Hellwig
2022-10-04  8:15                 ` Marek Behún
2022-10-04  8:17                   ` [PATCH] ARM: mvebu: select OF_DMA_DEFAULT_COHERENT if MACH_MVEBU_V7 Marek Behún
2022-10-04  8:30                     ` Christoph Hellwig
2022-10-04 12:54                       ` Marek Behún [this message]
2022-10-04  8:30                     ` Arnd Bergmann
2022-10-04  9:14                     ` Thorsten Leemhuis
2022-10-04  9:22                       ` Russell King (Oracle)
2022-10-04  9:56                 ` REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally" Robin Murphy
2022-10-04  7:25               ` Russell King (Oracle)
2022-10-04  8:30                 ` Marcin Wojtas
2022-10-04  9:08                   ` Russell King (Oracle)
2022-10-04 12:36                     ` Marek Behún
2022-10-04 12:59                       ` Marcin Wojtas
2022-10-04 18:51                         ` Pali Rohár
2022-10-04 19:35                           ` Marcin Wojtas
2022-10-04  8:26               ` Marek Behún
2022-10-04  8:36                 ` Marcin Wojtas
2022-10-20 18:22                   ` Russell King (Oracle)
2022-10-20 19:10                     ` Marek Behún
2022-10-21 16:25                     ` Linus Torvalds
2022-10-21 16:30                     ` Christoph Hellwig
2022-10-21 18:21                       ` Russell King (Oracle)
2022-10-23 11:58                     ` Klaus Kudielka
2022-10-03 18:57         ` Marek Behún
2022-10-01  9:31 ` Thorsten Leemhuis
2022-11-04 12:08   ` REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally" #forregzbot Thorsten Leemhuis

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