Re: [PATCH] MIPS: Fix support for Cavium Octeon debugger stub (v2).

[Ralf Baechle <ralf@linux-mips.org>]

On Mon, Jul 06, 2009 at 12:02:56PM -0700, David Daney wrote:

> The Cavium Octeon bootloader has a debugger stub that requires a
> little help from the target application to break in.
> 
> If configured, when we get an interrupt on the debug uart we wake up
> the debugger.
> 
> Changes from v1: Inline octeon_get_boot_debug_flag so it compiles
>                  without CONFIG_CAVIUM_GDB.
> 
> Signed-off-by: David Daney <ddaney@caviumnetworks.com>
> ---
>  arch/mips/Kconfig.debug               |   10 ++++++
>  arch/mips/cavium-octeon/serial.c      |   53 ++++++++++++++++++++++++++++++++-
>  arch/mips/cavium-octeon/setup.c       |    2 +-
>  arch/mips/include/asm/octeon/octeon.h |    1 -
>  4 files changed, 63 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
> index 364ca89..f6a0e68 100644
> --- a/arch/mips/Kconfig.debug
> +++ b/arch/mips/Kconfig.debug
> @@ -42,6 +42,16 @@ config SB1XXX_CORELIS
>  	  Select compile flags that produce code that can be processed by the
>  	  Corelis mksym utility and UDB Emulator.
>  
> +config CAVIUM_GDB
> +	bool "Remote GDB debugging using the Cavium Networks Multicore GDB"
> +	depends on DEBUG_KERNEL
> +	depends on CPU_CAVIUM_OCTEON
> +	select DEBUG_INFO
> +	help
> +	  If you say Y here, it will be possible to remotely debug the MIPS
> +	  kernel using the Cavium Networks GDB with extended SMP support.
> +	  This is only useful for kernel hackers. If unsure, say N.
> +
>  config RUNTIME_DEBUG
>  	bool "Enable run-time debugging"
>  	depends on DEBUG_KERNEL
> diff --git a/arch/mips/cavium-octeon/serial.c b/arch/mips/cavium-octeon/serial.c
> index 8240728..2110e68 100644
> --- a/arch/mips/cavium-octeon/serial.c
> +++ b/arch/mips/cavium-octeon/serial.c
> @@ -18,11 +18,60 @@
>  
>  #include <asm/octeon/octeon.h>
>  
> +#if defined(CONFIG_CAVIUM_GDB)
> +
>  #ifdef CONFIG_GDB_CONSOLE
>  #define DEBUG_UART 0
>  #else
>  #define DEBUG_UART 1
>  #endif
> +static irqreturn_t interrupt_debug_char(int cpl, void *dev_id)
> +{
> +	unsigned long lsrval;
> +	unsigned long tmp;
> +
> +	lsrval = cvmx_read_csr(CVMX_MIO_UARTX_LSR(DEBUG_UART));
> +	if (lsrval & 1) {
> +#ifdef CONFIG_KGDB
> +		/*
> +		 * The Cavium EJTAG bootmonitor stub is not compatible
> +		 * with KGDB.  We should never get here.
> +		 */
> +#error Illegal to use both CONFIG_KGDB and CONFIG_CAVIUM_GDB
> +#endif

#error is only acceptable to catch bugs in Kconfig or the code itself.  This
#error however is triggering on .config settings including such generated by
randconfig which is a PITA.  So rather please ensure forbidden .configs
can't be generated.  Alternatively, implement things such that both
config options can co-exist.

  Ralf