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

[Marcin Wojtas <mw@semihalf.com>]

Jeremy,

wt., 9 kwi 2019 o 06:03 Jeremy Linton <jeremy.linton@arm.com> napisał(a):
>
> Hi Marcin,
>
> On 4/8/19 8:31 PM, Marcin Wojtas wrote:
> > 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?
>
> Sorry, should have been more clear, this patch fixes normal ACPI console
> boot. You shouldn't need any parameters at all with recent kernels (i've
> been testing with mainline/5.1rc3/4) to get the console and boot log.
> AKA no 'console=', earlyprintk, earlycon, etc line at all.
>

I took the v5.1-rc3 and indeed it now boots without any parameter. That's great.

>
> To fix earlycon by itself (so you can see the boot log with just
> 'earlycon') only the baud rate change in the subject line is needed. But
> once I fixed that, I also wanted the console to work by default. That
> requires both the MMIO access type and the address to match between SPCR
> and the DSDT entry. Hence the long explanation about why I "broke"
> earlycon by changing the access type from GAS32 to GAS8. There is an
> existing "quirk" in the 8250_dw module for the armada parts for DT, and
> I suspect a similar thing is needed for ACPI (this might be a longer
> discussion elsewhere) because without it, I couldn't get a
> GAS32/MMIO32/reg_offset=2 combination to work. Hence my comment about
> changing the ACPI id for the console from the HISI identifier.
>

I always used earlycon with full parameter list, so I don't consider
the change as very problematic :) You can add my:
Tested-by: Marcin Wojtas <mw@semihalf.com>

Best regards,
Marcin

>
>
>
> >
> > 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
> >>
>