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Message-ID: <20231009125843.GA7272@lst.de> Date: Mon, 9 Oct 2023 14:58:44 +0200 From: Christoph Hellwig <hch@....de> To: Robin Murphy <robin.murphy@....com> Cc: Christoph Hellwig <hch@....de>, iommu@...ts.linux.dev, Marek Szyprowski <m.szyprowski@...sung.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, Wei Fang <wei.fang@....com>, Shenwei Wang <shenwei.wang@....com>, Clark Wang <xiaoning.wang@....com>, NXP Linux Team <linux-imx@....com>, linux-m68k@...ts.linux-m68k.org, netdev@...r.kernel.org, Jim Quinlan <james.quinlan@...adcom.com>, Greg Ungerer <gerg@...ux-m68k.org> Subject: Re: [PATCH 5/6] net: fec: use dma_alloc_noncoherent for m532x On Mon, Oct 09, 2023 at 11:29:12AM +0100, Robin Murphy wrote: > It looks a bit odd that this ends up applying to all of Coldfire, while the > associated cache flush only applies to the M532x platform, which implies > that we'd now be relying on the non-coherent allocation actually being > coherent on other Coldfire platforms. > > Would it work to do something like this to make sure dma-direct does the > right thing on such platforms (which presumably don't have caches?), and > then reduce the scope of this FEC hack accordingly, to clean things up even > better? Probably. Actually Greg comment something along the lines last time, and mentioned something about just instruction vs instruction and data cache. > > diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu > index b826e9c677b2..1851fa3fe077 100644 > --- a/arch/m68k/Kconfig.cpu > +++ b/arch/m68k/Kconfig.cpu > @@ -27,6 +27,7 @@ config COLDFIRE > select CPU_HAS_NO_BITFIELDS > select CPU_HAS_NO_CAS > select CPU_HAS_NO_MULDIV64 > + select DMA_DEFAULT_COHERENT if !MMU && !M523x Although it would probably make more sense to simply not select CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE and CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU for these platforms and not build the non-coherent code at all. This should also include all coldfire platforms with mmu (M54xx/M548x/M5441x). Then again for many of the coldfire platforms the Kconfig allows to select CACHE_WRITETHRU/CACHE_COPYBACK which looks related. Greg, any chance you could help out with the caching modes on coldfire and legacy m68knommu?
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