Re: [PATCH edk2-platforms v2 16/18] ARM/JunoPkg: Mapping Non-Trused SRAM as device memory

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 22 December 2017 at 19:08,  <evan.lloyd@arm.com> wrote:
> From: Girish Pathak <girish.pathak@arm.com>
>
> This fix changes the cache attribute of Non-Trusted SRAM on the Juno
> platform to device memory. This change is required to avoid coherency
> problems as Non-Trusted SRAM is used as a shared memory between the
> application processor and the SCP for communication. This change is a
> prerequisite for upcoming SCMI driver for the Juno platform.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Girish Pathak <girish.pathak@arm.com>

Evan, this needs your signoff as well I think?

Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> ---
>  Platform/ARM/JunoPkg/Library/ArmJunoLib/ArmJunoMem.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/Platform/ARM/JunoPkg/Library/ArmJunoLib/ArmJunoMem.c b/Platform/ARM/JunoPkg/Library/ArmJunoLib/ArmJunoMem.c
> index aa8d7d9c3b0d41e62d1849e6e88760e3066617f7..afb2db0050c65b0d1b2b69c9038e168755c152c1 100644
> --- a/Platform/ARM/JunoPkg/Library/ArmJunoLib/ArmJunoMem.c
> +++ b/Platform/ARM/JunoPkg/Library/ArmJunoLib/ArmJunoMem.c
> @@ -1,6 +1,6 @@
>  /** @file
>  *
> -*  Copyright (c) 2013-2015, ARM Limited. All rights reserved.
> +*  Copyright (c) 2013-2017, ARM Limited. All rights reserved.
>  *
>  *  This program and the accompanying materials
>  *  are licensed and made available under the terms and conditions of the BSD License
> @@ -111,7 +111,9 @@ ArmPlatformGetVirtualMemoryMap (
>    VirtualMemoryTable[++Index].PhysicalBase  = ARM_JUNO_NON_SECURE_SRAM_BASE;
>    VirtualMemoryTable[Index].VirtualBase     = ARM_JUNO_NON_SECURE_SRAM_BASE;
>    VirtualMemoryTable[Index].Length          = ARM_JUNO_NON_SECURE_SRAM_SZ;
> -  VirtualMemoryTable[Index].Attributes      = CacheAttributes;
> +  // This memory is shared between the application processor
> +  // and the SCP. To avoid coherency problems, map it as device memory.
> +  VirtualMemoryTable[Index].Attributes      = ARM_MEMORY_REGION_ATTRIBUTE_DEVICE;
>
>    // PCI Root Complex
>    VirtualMemoryTable[++Index].PhysicalBase  = PcdGet64 (PcdPcieControlBaseAddress);
> --
> Guid("CE165669-3EF3-493F-B85D-6190EE5B9759")
>