Re: [PATCH 3/3] Platform/RaspberryPi/AcpiTables: Correct _DMA consumer

["Samer El-Haj-Mahmoud" <samer.el-haj-mahmoud@arm.com>]

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I just got to this thread. Apologies for the delay.

I went through the ACPI spec. Here is what I see:

https://uefi.org/specs/ACPI/6.4/19_ASL_Reference/ACPI_Source_Language_Reference.html#qwordmemory-qword-memory-resource-descriptor-macro


"ResourceUsage specifies whether the Memory range is consumed by this device (ResourceConsumer) or passed on to child devices (ResourceProducer). If nothing is specified, then ResourceConsumer is assumed."



https://uefi.org/specs/ACPI/6.4/06_Device_Configuration/Device_Configuration.html#dma-direct-memory-access



" It specifies the ranges the bus controller (bridge) decodes on the child-side of its interface. (This is analogous to the _CRS object, which describes the resources that the bus controller decodes on the parent-side of its interface.) Any ranges described in the resources of a _DMA object can be used by child devices for DMA or bus master transactions.."



The way I read the spec, this wording in the _DMA definition "Any ranges described in the resources of a _DMA object can be used by child devices.." suggests that this should be a ResourceProducer, per the QWordMemory resource descriptor definition above


The _DMA example in section 6.2.4 uses a "ResourceConsumer", when it should really be "ResourceProducer" according to these definitions: It describes , the child devices view of the address range, so the "translation" added is the CPU's view of the same range.



I submitted a "code first" ECR to correct the ACPI spec example (here : https://bugzilla.tianocore.org/show_bug.cgi?id=3335). Please provide feedback on the BZ (or this thread) whether you agree or not, so we can take this to ASWG/UEFI Forum for discussion and approval



Thanks,

--Samer





From: Andrei Warkentin <awarkentin@vmware.com>
Sent: Thursday, April 8, 2021 10:24 AM
To: Jeremy Linton <Jeremy.Linton@arm.com>; devel@edk2.groups.io
Cc: Ard Biesheuvel <Ard.Biesheuvel@arm.com>; leif@nuviainc.com; pete@akeo.ie; Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
Subject: Re: [PATCH 3/3] Platform/RaspberryPi/AcpiTables: Correct _DMA consumer

I don't know... the ACPI spec is weird.

https://uefi.org/specs/ACPI/6.4/06_Device_Configuration/Device_Configuration.html#dma-direct-memory-access

...lists ResourceConsumer for _DMA.

A

________________________________
From: Jeremy Linton <jeremy.linton@arm.com<mailto:jeremy.linton@arm.com>>
Sent: Thursday, April 8, 2021 12:58 AM
To: devel@edk2.groups.io<mailto:devel@edk2.groups.io> <devel@edk2.groups.io<mailto:devel@edk2.groups.io>>
Cc: ard.biesheuvel@arm.com<mailto:ard.biesheuvel@arm.com> <ard.biesheuvel@arm.com<mailto:ard.biesheuvel@arm.com>>; leif@nuviainc.com<mailto:leif@nuviainc.com> <leif@nuviainc.com<mailto:leif@nuviainc.com>>; pete@akeo.ie<mailto:pete@akeo.ie> <pete@akeo.ie<mailto:pete@akeo.ie>>; samer.el-haj-mahmoud@arm.com<mailto:samer.el-haj-mahmoud@arm.com> <samer.el-haj-mahmoud@arm.com<mailto:samer.el-haj-mahmoud@arm.com>>; Andrei Warkentin <awarkentin@vmware.com<mailto:awarkentin@vmware.com>>; Jeremy Linton <jeremy.linton@arm.com<mailto:jeremy.linton@arm.com>>
Subject: [PATCH 3/3] Platform/RaspberryPi/AcpiTables: Correct _DMA consumer

Bridge devices should be marked as producers so that their
children can consume the resources. In linux if this isn't
true then the translation gets ignored and the DMA values
are incorrect. This fixes DMA on all the devices that
need a translation.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com<mailto:jeremy.linton@arm.com>>
---
 Platform/RaspberryPi/AcpiTables/Dsdt.asl | 2 +-
 Platform/RaspberryPi/AcpiTables/Emmc.asl | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Platform/RaspberryPi/AcpiTables/Dsdt.asl b/Platform/RaspberryPi/AcpiTables/Dsdt.asl
index d116f965e1..32cd5fc9f9 100644
--- a/Platform/RaspberryPi/AcpiTables/Dsdt.asl
+++ b/Platform/RaspberryPi/AcpiTables/Dsdt.asl
@@ -205,7 +205,7 @@ DefinitionBlock ("Dsdt.aml", "DSDT", 5, "RPIFDN", "RPI", 2)
         // Only the first GB is available.

         // Bus 0xC0000000 -> CPU 0x00000000.

         //

-        QWordMemory (ResourceConsumer,

+        QWordMemory (ResourceProducer,

           ,

           MinFixed,

           MaxFixed,

diff --git a/Platform/RaspberryPi/AcpiTables/Emmc.asl b/Platform/RaspberryPi/AcpiTables/Emmc.asl
index 179dd3ecdb..0fbc2a79ea 100644
--- a/Platform/RaspberryPi/AcpiTables/Emmc.asl
+++ b/Platform/RaspberryPi/AcpiTables/Emmc.asl
@@ -32,7 +32,7 @@ DefinitionBlock (__FILE__, "SSDT", 5, "RPIFDN", "RPI4EMMC", 2)
       }



       Name (_DMA, ResourceTemplate() {

-        QWordMemory (ResourceConsumer,

+        QWordMemory (ResourceProducer,

           ,

           MinFixed,

           MaxFixed,

--
2.13.7
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