Messages in this thread | | | Date | Fri, 19 Aug 2022 15:34:14 -0700 | Subject | Re: [PATCH] powerpc: Add support for early debugging via Serial 16550 console | From | Randy Dunlap <> |
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Hi--
On 8/19/22 14:12, Pali Rohár wrote: > Currently powerpc early debugging contains lot of platform specific > options, but does not support standard UART / serial 16550 console. > > Later legacy_serial.c code supports registering UART as early debug console > from device tree but it is not early during booting, but rather later after > machine description code finishes. > > So for real early debugging via UART is current code unsuitable. > > Add support for new early debugging option CONFIG_PPC_EARLY_DEBUG_16550 > which enable Serial 16550 console on address defined by new option > CONFIG_PPC_EARLY_DEBUG_16550_PHYSADDR and by stride by option > CONFIG_PPC_EARLY_DEBUG_16550_STRIDE. > > With this change it is possible to debug powerpc machine descriptor code. > For example this early debugging code can print on serial console also > "No suitable machine description found" error which is done before > legacy_serial.c code. > > Signed-off-by: Pali Rohár <pali@kernel.org> > --- > Tested on P2020 board. It allowed me do debug and implement this patch series: > https://lore.kernel.org/linuxppc-dev/20220819191557.28116-1-pali@kernel.org/ > --- > arch/powerpc/Kconfig.debug | 14 ++++++++++++++ > arch/powerpc/include/asm/udbg.h | 1 + > arch/powerpc/kernel/udbg.c | 2 ++ > arch/powerpc/kernel/udbg_16550.c | 33 ++++++++++++++++++++++++++++++++ > 4 files changed, 50 insertions(+) > > diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug > index 9f363c143d86..a4e7d90a45d2 100644 > --- a/arch/powerpc/Kconfig.debug > +++ b/arch/powerpc/Kconfig.debug > @@ -276,6 +276,11 @@ config PPC_EARLY_DEBUG_OPAL_HVSI > Select this to enable early debugging for the PowerNV platform > using an "hvsi" console > > +config PPC_EARLY_DEBUG_16550 > + bool "Serial 16550" > + help > + Select this to enable early debugging via Serial 16550 console > + > config PPC_EARLY_DEBUG_MEMCONS > bool "In memory console" > help > @@ -355,6 +360,15 @@ config PPC_EARLY_DEBUG_CPM_ADDR > platform probing is done, all platforms selected must > share the same address. > > +config PPC_EARLY_DEBUG_16550_PHYSADDR > + hex "Early debug Serial 16550 physical address" > + depends on PPC_EARLY_DEBUG_16550
Is there any chance that you could provide a default value here so that 'make olddefconfig' does not end up like it does without having a default value?
CONFIG_PPC_EARLY_DEBUG_16550=y # CONFIG_PPC_EARLY_DEBUG_MEMCONS is not set CONFIG_PPC_EARLY_DEBUG_16550_PHYSADDR= CONFIG_PPC_EARLY_DEBUG_16550_STRIDE=1
which then causes a kconfig prompt when starting the build...
> + > +config PPC_EARLY_DEBUG_16550_STRIDE > + int "Early debug Serial 16550 stride" > + depends on PPC_EARLY_DEBUG_16550 > + default 1 > + > config FAIL_IOMMU > bool "Fault-injection capability for IOMMU" > depends on FAULT_INJECTION
Thanks. -- ~Randy
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