Re: [PATCH 6/6] arm64: document the choice of page attributes for pgprot_dmacoherent
On Fri, Aug 16, 2019 at 07:59:42PM +0200, Christoph Hellwig wrote: > On Fri, Aug 16, 2019 at 06:31:18PM +0100, Will Deacon wrote: > > Mind if I tweak the second sentence to be: > > > > This is different from "Device-nGnR[nE]" memory which is intended for MMIO > > and thus forbids speculation, preserves access size, requires strict > > alignment and can also force write responses to come from the endpoint. > > > > ? It's a small change, but it better fits with the arm64 terminology > > ("strongly ordered" is no longer used in the architecture). > > > > If you're happy with that, I can make the change and queue this patch > > for 5.4. > > I'm fine with the change, but you really need this series as base, > as there is no pgprot_dmacoherent before the series. So I think I'll > have to queue it up if we want it for 5.4, and I'll need a few more > reviews for the other patches in this series first. Ah, I didn't think about the contextual stuff. In which case, with my change in wording: Acked-by: Will Deacon and feel free to route it with the rest. Thanks, Will
Re: [PATCH 6/6] arm64: document the choice of page attributes for pgprot_dmacoherent
On Fri, Aug 16, 2019 at 06:31:18PM +0100, Will Deacon wrote: > Mind if I tweak the second sentence to be: > > This is different from "Device-nGnR[nE]" memory which is intended for MMIO > and thus forbids speculation, preserves access size, requires strict > alignment and can also force write responses to come from the endpoint. > > ? It's a small change, but it better fits with the arm64 terminology > ("strongly ordered" is no longer used in the architecture). > > If you're happy with that, I can make the change and queue this patch > for 5.4. I'm fine with the change, but you really need this series as base, as there is no pgprot_dmacoherent before the series. So I think I'll have to queue it up if we want it for 5.4, and I'll need a few more reviews for the other patches in this series first.
Re: [PATCH 6/6] arm64: document the choice of page attributes for pgprot_dmacoherent
On Fri, Aug 16, 2019 at 06:31:18PM +0100, Will Deacon wrote: > Hi Christoph, > > Thanks for spinning this into a patch. > > On Fri, Aug 16, 2019 at 09:07:54AM +0200, Christoph Hellwig wrote: > > Based on an email from Will Deacon. > > > > Signed-off-by: Christoph Hellwig > > --- > > arch/arm64/include/asm/pgtable.h | 8 > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/arm64/include/asm/pgtable.h > > b/arch/arm64/include/asm/pgtable.h > > index 6700371227d1..6ff221d9a631 100644 > > --- a/arch/arm64/include/asm/pgtable.h > > +++ b/arch/arm64/include/asm/pgtable.h > > @@ -435,6 +435,14 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd) > > __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_NC) | > > PTE_PXN | PTE_UXN) > > #define pgprot_device(prot) \ > > __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_DEVICE_nGnRE) > > | PTE_PXN | PTE_UXN) > > +/* > > + * DMA allocations for non-coherent devices use what the Arm architecture > > calls > > + * "Normal non-cacheable" memory, which permits speculation, unaligned > > accesses > > + * and merging of writes. This is different from "Strongly Ordered" memory > > + * which is intended for MMIO and thus forbids speculation, preserves > > access > > + * size, requires strict alignment and also forces write responses to come > > from > > + * the endpoint. > > + */ > > Mind if I tweak the second sentence to be: > > This is different from "Device-nGnR[nE]" memory which is intended for MMIO > and thus forbids speculation, preserves access size, requires strict > alignment and can also force write responses to come from the endpoint. > > ? It's a small change, but it better fits with the arm64 terminology > ("strongly ordered" is no longer used in the architecture). > > If you're happy with that, I can make the change and queue this patch > for 5.4. FWIW, with that wording: Acked-by: Mark Rutland Mark.
Re: [PATCH 6/6] arm64: document the choice of page attributes for pgprot_dmacoherent
Hi Christoph, Thanks for spinning this into a patch. On Fri, Aug 16, 2019 at 09:07:54AM +0200, Christoph Hellwig wrote: > Based on an email from Will Deacon. > > Signed-off-by: Christoph Hellwig > --- > arch/arm64/include/asm/pgtable.h | 8 > 1 file changed, 8 insertions(+) > > diff --git a/arch/arm64/include/asm/pgtable.h > b/arch/arm64/include/asm/pgtable.h > index 6700371227d1..6ff221d9a631 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -435,6 +435,14 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd) > __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_NORMAL_NC) | > PTE_PXN | PTE_UXN) > #define pgprot_device(prot) \ > __pgprot_modify(prot, PTE_ATTRINDX_MASK, PTE_ATTRINDX(MT_DEVICE_nGnRE) > | PTE_PXN | PTE_UXN) > +/* > + * DMA allocations for non-coherent devices use what the Arm architecture > calls > + * "Normal non-cacheable" memory, which permits speculation, unaligned > accesses > + * and merging of writes. This is different from "Strongly Ordered" memory > + * which is intended for MMIO and thus forbids speculation, preserves access > + * size, requires strict alignment and also forces write responses to come > from > + * the endpoint. > + */ Mind if I tweak the second sentence to be: This is different from "Device-nGnR[nE]" memory which is intended for MMIO and thus forbids speculation, preserves access size, requires strict alignment and can also force write responses to come from the endpoint. ? It's a small change, but it better fits with the arm64 terminology ("strongly ordered" is no longer used in the architecture). If you're happy with that, I can make the change and queue this patch for 5.4. Thanks, Will