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Date: Tue, 24 Jun 2014 17:26:02 -0700 (PDT) From: David Rientjes <rientjes@...gle.com> To: Mark Salter <msalter@...hat.com> cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] arm64: fix CONFIG_ZONE_DMA on systems with no 32-bit addressable DRAM On Mon, 23 Jun 2014, Mark Salter wrote: > Commit 2d5a5612bc (arm64: Limit the CMA buffer to 32-bit if ZONE_DMA) > forces the CMA buffer to be 32-bit addressable if CONFIG_ZONE_DMA is > defined. This breaks CMA on platforms with no 32-bit addressable DRAM. > This patch checks to make sure there is 32-bit addressable DRAM before > setting the 32-bit limit. If there is none, no limit is placed on the > CMA buffer. This allows a single kernel (with CONFIG_ZONE_DMA defined) > to support platforms requiring the 32-bit limit and platforms with no > 32-bit limit. > > Signed-off-by: Mark Salter <msalter@...hat.com> > --- > arch/arm64/mm/init.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index c5415e2..2925576 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -149,8 +149,17 @@ void __init arm64_memblock_init(void) > early_init_fdt_scan_reserved_mem(); > > /* 4GB maximum for 32-bit only capable devices */ > - if (IS_ENABLED(CONFIG_ZONE_DMA)) > + if (IS_ENABLED(CONFIG_ZONE_DMA)) { > dma_phys_limit = dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1; > + /* > + * If platform doesn't have DRAM within the dma_phys_limit, > + * remove the limit altogether. This allows one kernel (with > + * CONFIG_ZONE_DMA defined) to support platforms with 32-bit > + * only devices and platforms with no 32-bit DRAM. > + */ > + if (dma_phys_limit <= memblock_start_of_DRAM()) > + dma_phys_limit = 0; > + } > dma_contiguous_reserve(dma_phys_limit); > > memblock_allow_resize(); It is a shame that we have very similar logic, all dependent on memblock_start_of_DRAM(), in both zone_sizes_init() and arm64_memblock_init() and the latter having to be called before the former. I assume there's no way to make this cleaner in the bootstrap code so the dma_to_phys(NULL, DMA_BIT_MASK(32)) + 1 limit can be handled properly in a single location? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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