On Mon, Nov 02, 2015 at 09:51:46AM -0600, Suravee Suthikulanit wrote:
> Hi Dennis / Hanjun,
>
> On 11/2/2015 5:58 AM, Hanjun Guo wrote:
> >Hi Dennis,
> >
> >On 11/02/2015 12:02 PM, Dennis Chen wrote:
> >>On Thu, Oct 29, 2015 at 6:50 AM, Suravee Suthikulpanit
> >><Suravee.Suthikulpanit@xxxxxxx> wrote:
> >>>From: Jeremy Linton <jeremy.linton@xxxxxxx>
> >>>
> >>>ACPI configurations can now mark devices as noncoherent,
> >>>support that choice.
> >>>
> >>>NOTE: This is required to support USB on ARM Juno Development Board.
> >>>
> >>>Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> >>>Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> >>>CC: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> >>>CC: Catalin Marinas <catalin.marinas@xxxxxxx>
> >>>CC: Rob Herring <robh+dt@xxxxxxxxxx>
> >>>CC: Will Deacon <will.deacon@xxxxxxx>
> >>>CC: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> >>>---
> >>> include/acpi/acpi_bus.h | 5 +++--
> >>> 1 file changed, 3 insertions(+), 2 deletions(-)
> >>>
> >>>diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> >>>index d11eff8..0f131d2 100644
> >>>--- a/include/acpi/acpi_bus.h
> >>>+++ b/include/acpi/acpi_bus.h
> >>>@@ -407,7 +407,7 @@ static inline bool acpi_check_dma(struct
> >>>acpi_device *adev, bool *coherent)
> >>> * case 1. Do not support and disable DMA.
> >>> * case 2. Support but rely on arch-specific cache maintenance for
> >>> * non-coherence DMA operations.
> >>>- * Currently, we implement case 1 above.
> >>>+ * Currently, we implement case 2 above.
> >>> *
> >>> * For the case when _CCA is missing (i.e. cca_seen=0) and
> >>> * platform specifies ACPI_CCA_REQUIRED, we do not support DMA,
> >>>@@ -415,7 +415,8 @@ static inline bool acpi_check_dma(struct
> >>>acpi_device *adev, bool *coherent)
> >>> *
> >>> * See acpi_init_coherency() for more info.
> >>> */
> >>>- if (adev->flags.coherent_dma) {
> >>>+ if (adev->flags.coherent_dma ||
> >>>+ (adev->flags.cca_seen && IS_ENABLED(CONFIG_ARM64))) {
> >>> ret = true;
> >>> if (coherent)
> >>> *coherent = adev->flags.coherent_dma;
> >>
> >>Hi Suravee,
> >>
> >>The acpi_check_dma function has been removed in patch 6 of this patch
> >>set, why it is still be used
> >>here, am I missing something? If the acpi_check_dma will be used in
> >>the future, personally I'd like
> >
> >I think this patch just to let people know that there is
> >case that arch-specific cache maintenance is still needed
> >for ACPI (such as Juno board), and in the later patches will
> >cover this case.
> >
> >acpi_check_dma() will be replaced by acpi_get_dma_attr(),
> >and in acpi_get_dma_attr() will cover that case and will
> >be easily understood. (Suravee, correct me if I'm wrong :) )
>
> Thanks Hanjun for filling in the info.
>
> Yes, this is mainly to document the logic changes required by Juno,
> which would be more clear than just merging this change in the later
> patch.
>
Clear.
> >>to use IS_ENABLED(CONFIG_ACPI_CCA_REQUIRED) while not CONFIG_ARM64
> >>macro here,
>
> We could have used CONFIG_ACPI_CCA_REQUIRED here, but this will be
> replaced by logic in patch 5, and removed in patch 6 anyways. So, I
> think it is okay. Eventually, the rest of the logic will be using
> CONFIG_ACPI_CCA_REQUIRED.
>
> or since _CCA attribute
> >>is arch-specific, it's reasonable to leave the _CCA handling policy to
> >>the arch-specific code. For example,
> >>with a link weak function like acpi_arch_check_dma() as a default
> >>handling if no arch-specific code
> >>provided, the actual _CCA handling will be implemented in the ARM,
> >>Intel or other Arch if required.
> >
> >Actually Intel platform don't need _CCA and it's coherent
> >in default, since _CCA is in ACPI spec, I would like it's
> >handled in ACPI core.
> >
> >Thanks
> >Hanjun
>
> I also agree with Hanjun that the CCA parsing should be handled by
> the ACPI core driver. Since we are using the
> CONFIG_ACPI_CCA_REQUIRED, we should not need to have arch-specific
> code. If the ACPI spec gets more complicate in the future, we can
> revisit this. :)
>
Hmm, seems I have no objection currently if we only think about intel and
arm arch. Things maybe a little bit complicated if more Archs becomes
ACPI awareness, if any. Good to see the patch set upstream soon :) Thank you
Suravee and Hanjun.
> Thanks,
> Suravee
>
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