[edk2-devel] [PATCH edk2-platforms 4/5] Platform/RaspberryPi3: query firmware for 16550 input clock at boot
Pete Batard
pete at akeo.ie
Wed May 6 10:18:58 UTC 2020
One remark below:
On 2020.05.05 19:11, Ard Biesheuvel wrote:
> On 5/5/20 4:50 PM, Ard Biesheuvel wrote:
>> Query the firmware for the clock rate that is used to drive the
>> 16550 baud clock, so that we can program the correct baud rate.
>>
>> Co-authored-by: Pete Batard <pete at akeo.ie>
>> Co-authored-by: Andrei Warkentin <andrey.warkentin at gmail.com>
>> Co-authored-by: Ard Biesheuvel <ard.biesheuvel at arm.com>
>> Signed-off-by: Pete Batard <pete at akeo.ie>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at arm.com>
>> ---
>> Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
>> | 25 +++++++++++++++++++-
>> 1 file changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git
>> a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
>> b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
>> index 91dfe1bb981e..35580e4ed73a 100644
>> ---
>> a/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
>> +++
>> b/Platform/RaspberryPi/Library/PlatformLib/AArch64/RaspberryPiHelper.S
>> @@ -3,7 +3,7 @@
>> * Copyright (c) 2020, Andrei Warkentin <andrey.warkentin at gmail.com>
>> * Copyright (c) 2019-2020, Pete Batard <pete at akeo.ie>
>> * Copyright (c) 2016, Linaro Limited. All rights reserved.
>> - * Copyright (c) 2011-2013, ARM Limited. All rights reserved.
>> + * Copyright (c) 2011-2020, ARM Limited. All rights reserved.
>> *
>> * SPDX-License-Identifier: BSD-2-Clause-Patent
>> *
>> @@ -85,6 +85,14 @@ ASM_FUNC (ArmPlatformPeiBootAction)
>> adr x2, mBoardRevision
>> str w0, [x2]
>> +#if (RPI_MODEL == 3)
>
> As noted by Pete off-list, doing this doesn't work unless we add
> something like
>
> GCC:*_*_*_PP_FLAGS = -DRPI_MODEL=3
>
> to the [BuildOptions] in RPi3.dsc
>
>
>
>> + run .Lclkinfo_buffer
>> +
>> + ldr w0, .Lfrequency
>> + adrp x2, _gPcd_BinaryPatch_PcdSerialClockRate
>> + str w0, [x2, :lo12:_gPcd_BinaryPatch_PcdSerialClockRate]
>> +#endif
>> +
Since we're modifying a patchable PCD here, shouldn't we add a:
[PatchPcd]
gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate
section in PlatformLib.inf?
Of course, if we do that, we can't keep PcdSerialClockRate fixed for
RPi4, as the build process will complain about PCD mismatch.
I also wouldn't mind a comment that explains how one arrives at figuring
out that "_gPcd_BinaryPatch_PcdSerialClockRate" should be used to locate
our address (and possibly the addition of :lo12:), because I don't think
it's going to be that straightforward for people reading the code for
the first time, though I fear that the explanation will boil down to "we
need to do it this specific way for a gcc aarch64 relocation"...
>> ret
>> .align 4
>> @@ -127,6 +135,21 @@ ASM_FUNC (ArmPlatformPeiBootAction)
>> .long 0 // end tag
>> .set .Lrevinfo_size, . - .Lrevinfo_buffer
>> +#if (RPI_MODEL == 3)
>> + .align 4
>> +.Lclkinfo_buffer:
>> + .long .Lclkinfo_size
>> + .long 0x0
>> + .long RPI_MBOX_GET_CLOCK_RATE
>> + .long 8 // buf size
>> + .long 4 // input len
>> + .long 4 // clock id: 0x04 = Core/VPU
>> +.Lfrequency:
>> + .long 0 // frequency
>> + .long 0 // end tag
>> + .set .Lclkinfo_size, . - .Lclkinfo_buffer
>> +#endif
>> +
>> //UINTN
>> //ArmPlatformGetPrimaryCoreMpId (
>> // VOID
>>
>
>
>
>
With addition of "GCC:*_*_*_PP_FLAGS = -DRPI_MODEL=3" in the .dsc:
Reviewed-by: Pete Batard <pete at akeo.ie>
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