From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Marcin Wojtas <mw@semihalf.com>
Cc: "Marek Behún" <kabel@kernel.org>,
pali@kernel.org, "Christoph Hellwig" <hch@lst.de>,
"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: REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally"
Date: Tue, 4 Oct 2022 10:08:15 +0100 [thread overview]
Message-ID: <Yzv3/zM5vMaPSrMS@shell.armlinux.org.uk> (raw)
In-Reply-To: <CAPv3WKeWDWGaMs4VxcLb01tzEz+1pVs5do_MbMdOpvOC7J_DTw@mail.gmail.com>
On Tue, Oct 04, 2022 at 10:30:40AM +0200, Marcin Wojtas wrote:
> Thanks for the explanation and I agree with your reasoning. Therefore
> the below should be sufficient if we use HW BM and non-coherent
> setting:
>
> --- a/drivers/net/ethernet/marvell/mvneta_bm.c
> +++ b/drivers/net/ethernet/marvell/mvneta_bm.c
> @@ -103,7 +103,7 @@ int mvneta_bm_construct(struct hwbm_pool
> *hwbm_pool, void *buf)
> */
> *(u32 *)buf = (u32)buf;
> phys_addr = dma_map_single(&priv->pdev->dev, buf, bm_pool->buf_size,
> - DMA_FROM_DEVICE);
> + DMA_BIDIRECTIONAL);
> if (unlikely(dma_mapping_error(&priv->pdev->dev, phys_addr)))
> return -ENOMEM;
>
> Marek - can you please confirm that?
This is insufficient. Marek's patch is the correct version.
The DMA API requires that the direction argument is the same for
mapping, unmapping and syncing a region.
> > I did notice that there was no dma-coherent markings in DT, which means
> > that the DMA API will assume the device is non-coherent, and cache
> > maintenance will be performed. If it is dma-coherent, then cache
> > maintenance won't be performed, and DT needs to be updated to indicate
> > this.
> >
> > If firmware is making the devices DMA coherent, and it's under firmware
> > control, then shouldn't firmware also be updating the kernel's device
> > tree to indicate how it's configured the hardware coherency?
> >
>
> Imo there are too many boxes out there and updating firmware in the
> field is rather no-go. We already handle this in kernel / DT in big
> extent, so I think we should stick to that path.
Seemingly, we don't handle it "well enough" in the kernel, since with
Christoph's change, we end up with the devices being non-coherent.
Yes, the kernel needs fixing to work with older firmware, but I think
firmware should also be fixed.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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next prev parent reply other threads:[~2022-10-04 9:09 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
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) [this message]
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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