Re: [PATCH] Marvell/Armada7k8k: Remove SPCR baud rate setting

[Marcin Wojtas <mw@semihalf.com>]

Hi Jeremy,

Thanks for the patch. However I played with booting with ACPI with and
without your patch - I may be missing something, but I don't see a
difference, when using earlycon (both
'earlycon=uart,mmio32,0xf0512000' and
'earlycon=uart8250,mmio32,0xf0512000'). Can you please show what
booting scenario is fixed with the patch?

Thanks,
Marcin

wt., 9 kwi 2019 o 02:33 Jeremy Linton <jeremy.linton@arm.com> napisał(a):
>
> The mcbin (and likely others) have a nonstandard uart clock.
> This means that the earlycon programming will incorrectly set
> the baud rate if it is specified. The way around this is to tell
> the kernel to continue using the preprogrammed baud rate. This
> is done by setting the baud to 0.
>
> Further, the SPCR and DSDT serial port need to match the port
> address and port access type for the kernel to conclude they
> are the same.
>
> So while ARM_GAS32 is correct for earlycon (it can be used alone
> on the  kernel command line) by providing the reg-shift=2 value,
> it also sets the io type to MMIO32, which doesn't match the DSDT
> defined MMIO. This means that the actual console will never appear.
> The obvious fix is to set reg-width=4 in DSDT, but that also changes
> the accesssors to 32-bits (similarly to earlycon) and results in
> console failure.
>
> So the less obvious fix, is to use the GAS8 specifier. This means
> that earlycon needs to be fully specified as
> earlycon=uart,mmio32,0xf0512000, but has the extremely useful feature
> that the console default works without any user interaction.
>
> If in the future marvell decides to define their own ACPI id for the
> console and upstream a quirk, the ARM_GAS8 portion of this should
> be reverted.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
>  Silicon/Marvell/Armada7k8k/AcpiTables/Spcr.aslc | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Silicon/Marvell/Armada7k8k/AcpiTables/Spcr.aslc b/Silicon/Marvell/Armada7k8k/AcpiTables/Spcr.aslc
> index e78bb9036f..06c7af069c 100644
> --- a/Silicon/Marvell/Armada7k8k/AcpiTables/Spcr.aslc
> +++ b/Silicon/Marvell/Armada7k8k/AcpiTables/Spcr.aslc
> @@ -30,11 +30,11 @@ EFI_ACPI_SERIAL_PORT_CONSOLE_REDIRECTION_TABLE Spcr = {
>    { EFI_ACPI_RESERVED_BYTE,
>      EFI_ACPI_RESERVED_BYTE,
>      EFI_ACPI_RESERVED_BYTE },                                           // Reserved1[3]
> -  ARM_GAS32 (FixedPcdGet64(PcdSerialRegisterBase)),                     // BaseAddress
> +  ARM_GAS8 (FixedPcdGet64(PcdSerialRegisterBase)),                      // BaseAddress
>    EFI_ACPI_SERIAL_PORT_CONSOLE_REDIRECTION_TABLE_INTERRUPT_TYPE_GIC,    // InterruptType
>    0,                                                                    // Irq
>    51,                                                                   // GlobalSystemInterrupt
> -  EFI_ACPI_SERIAL_PORT_CONSOLE_REDIRECTION_TABLE_BAUD_RATE_115200,      // BaudRate
> +  0,                                                                    // Keep Firmware Baud
>    EFI_ACPI_SERIAL_PORT_CONSOLE_REDIRECTION_TABLE_PARITY_NO_PARITY,      // Parity
>    EFI_ACPI_SERIAL_PORT_CONSOLE_REDIRECTION_TABLE_STOP_BITS_1,           // StopBits
>    0,                                                                    // FlowControl
> --
> 2.20.1
>