[edk2-devel] [PATCH edk2-platforms 3/5] Platform/RaspberryPi: fix 16550 divisor calculation logic
Ard Biesheuvel
ard.biesheuvel at arm.com
Wed May 6 10:25:01 UTC 2020
On 5/6/20 12:18 PM, Pete Batard wrote:
> One general remark below:
>
> On 2020.05.05 19:10, Ard Biesheuvel wrote:
>> On 5/5/20 4:50 PM, Ard Biesheuvel wrote:
>>> The 16550 'miniUART' on the Raspberry Pi gets its input clock from
>>> different sources on RPi3 and RPi3. Fix the logic that derives the
>>
>> This should be 'Rpi3 and RPi4'
>>
>>> divisor for the 16550 baud clock on the respective platforms.
>>>
>>> While at it, make the input clock PCD patchable for RPi3 so we can
>>> manipulate it at runtime in a future patch.
>
> For the sake of harmonization between platforms, wouldn't we want to
> also declare the PCD patchable on RPi4 as well (even though we obviously
> aren't going to patch it for the time being)?
>
I'd prefer not to. That way, we can easily spot problems when the
patching code is incorporated inadvertently.
> There is some plan of factorizing the DSC content, so if that doesn't
> hurt us, I'd propose we try to keep the Pi3 and Pi4 version as close as
> possible.
>
> This also ties in with my remark for the next patch.
>
>>>
>>> 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/RPi3/RPi3.dsc | 4 +++-
>>> Platform/RaspberryPi/RPi4/RPi4.dsc | 2 +-
>>> Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
>>> | 14 ++++++++------
>>> 3 files changed, 12 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/Platform/RaspberryPi/RPi3/RPi3.dsc
>>> b/Platform/RaspberryPi/RPi3/RPi3.dsc
>>> index d7218219fc5a..96b27400eef8 100644
>>> --- a/Platform/RaspberryPi/RPi3/RPi3.dsc
>>> +++ b/Platform/RaspberryPi/RPi3/RPi3.dsc
>>> @@ -409,7 +409,6 @@ [PcdsFixedAtBuild.common]
>>> gArmPlatformTokenSpaceGuid.PL011UartClkInHz|48000000
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio|TRUE
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterStride|4
>>> - gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|500000000
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialFifoControl|0x27
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialExtendedTxFifoSize|8
>>> gEfiMdePkgTokenSpaceGuid.PcdUartDefaultBaudRate|115200
>>> @@ -441,6 +440,9 @@ [PcdsFixedAtBuild.common]
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareVendor|L"EDK2"
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack|TRUE
>>> +[PcdsPatchableInModule]
>>> + gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|250000000
>>> +
>>> [PcdsDynamicHii.common.DEFAULT]
>>> #
>>> diff --git a/Platform/RaspberryPi/RPi4/RPi4.dsc
>>> b/Platform/RaspberryPi/RPi4/RPi4.dsc
>>> index 4fb015b077e6..5d8bd88d7e34 100644
>>> --- a/Platform/RaspberryPi/RPi4/RPi4.dsc
>>> +++ b/Platform/RaspberryPi/RPi4/RPi4.dsc
>>> @@ -420,7 +420,7 @@ [PcdsFixedAtBuild.common]
>>> gArmPlatformTokenSpaceGuid.PL011UartClkInHz|48000000
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialUseMmio|TRUE
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialRegisterStride|4
>>> - gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|500000000
>>> + gEfiMdeModulePkgTokenSpaceGuid.PcdSerialClockRate|1000000000
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialFifoControl|0x27
>>> gEfiMdeModulePkgTokenSpaceGuid.PcdSerialExtendedTxFifoSize|8
>>> gEfiMdePkgTokenSpaceGuid.PcdUartDefaultBaudRate|115200
>>> diff --git
>>> a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
>>> b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
>>> index b1d17d3fa04a..5e83bbf022eb 100644
>>> --- a/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
>>> +++ b/Platform/RaspberryPi/Library/DualSerialPortLib/DualSerialPortLib.c
>>> @@ -41,18 +41,20 @@ SerialPortGetDivisor (
>>> // On the Raspberry Pi, the clock to use for the 16650-compatible
>>> UART
>>> // is the base clock divided by the 12.12 fixed point VPU clock
>>> divisor.
>>> //
>>> - BaseClockRate = (UINT64)PcdGet32 (PcdSerialClockRate) * 4;
>>> + BaseClockRate = (UINT64)PcdGet32 (PcdSerialClockRate);
>>> +#if (RPI_MODEL == 4)
>>> Divisor = MmioRead32(BCM2836_CM_BASE +
>>> BCM2836_CM_VPU_CLOCK_DIVISOR) & 0xFFFFFF;
>>> if (Divisor != 0)
>>> BaseClockRate = (BaseClockRate << 12) / Divisor;
>>> +#endif
>>> //
>>> - // Now calculate divisor for baud generator
>>> - // Ref_Clk_Rate / Baud_Rate / 16
>>> + // As per the BCM2xxx datasheets:
>>> + // baudrate = system_clock_freq / (8 * (divisor + 1)).
>>> //
>>> - Divisor = (UINT32)BaseClockRate / (SerialBaudRate * 16);
>>> - if (((UINT32)BaseClockRate % (SerialBaudRate * 16)) >=
>>> SerialBaudRate * 8) {
>>> - Divisor++;
>>> + Divisor = (UINT32)BaseClockRate / (SerialBaudRate * 8);
>>> + if (Divisor != 0) {
>>> + Divisor--;
>>> }
>>> return Divisor;
>>> }
>>>
>>
>>
>>
>>
>
> Reviewed-by: Pete Batard <pete at akeo.ie>
>
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#58695): https://edk2.groups.io/g/devel/message/58695
Mute This Topic: https://groups.io/mt/73999456/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-
More information about the edk2-devel-archive
mailing list