[Skiboot] [PATCH 2/2] astbmc: Enable mbox depending on scratch reg

[Joel Stanley]

On Wed, Feb 28, 2018 at 4:46 PM, Joel Stanley <joel at jms.id.au> wrote:
> P8 boxes can opt in for mbox pnor support if they set the scratch
> register bit to indicate it is supported.
>
> Signed-off-by: Joel Stanley <joel at jms.id.au>
> ---

I've tested this with the following configurations:

P8 test platform is Palmetto, and P9 test platform is Romulus.

mbox aware BMC, scatch reg set: P9, P8
mbox aware BMC, scratch reg unset: P8, P9
mbox unaware BMC, scratch reg unset: P8

All systems booted using the expected flash access mechanism. For
"fun", you can chose to set/unset the scratch register between boots
and have your host firmware change behaviour.

Cheers,

Joel

>  hw/ast-bmc/ast-io.c       | 14 ++++++++++++++
>  include/ast.h             |  1 +
>  platforms/astbmc/common.c |  5 +++--
>  3 files changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ast-bmc/ast-io.c b/hw/ast-bmc/ast-io.c
> index cd1aba2a177a..964d41513379 100644
> --- a/hw/ast-bmc/ast-io.c
> +++ b/hw/ast-bmc/ast-io.c
> @@ -116,6 +116,7 @@
>   */
>
>  #define BMC_SIO_SCR29 0x29
> +#define BMC_SIO_SCR29_MBOX 0x08
>  #define BMC_SIO_SCR29_MEMBOOT 0x10
>
>  enum {
> @@ -427,6 +428,19 @@ bool ast_is_ahb_lpc_pnor(void)
>         return !(boot_flags & BMC_SIO_SCR29_MEMBOOT);
>  }
>
> +bool ast_scratch_reg_is_mbox(void)
> +{
> +       uint8_t boot_version;
> +       uint8_t boot_flags;
> +
> +       boot_version = bmc_sio_inb(BMC_SIO_SCR28);
> +       if (boot_version != BOOT_FLAGS_VERSION)
> +               return false;
> +
> +       boot_flags = bmc_sio_inb(BMC_SIO_SCR29);
> +       return boot_flags & BMC_SIO_SCR29_MBOX;
> +}
> +
>  void ast_setup_ibt(uint16_t io_base, uint8_t irq)
>  {
>         uint32_t v;
> diff --git a/include/ast.h b/include/ast.h
> index 414ff6a3d39a..2c1336b2a79b 100644
> --- a/include/ast.h
> +++ b/include/ast.h
> @@ -82,6 +82,7 @@ int ast_copy_from_ahb(void *dst, uint32_t reg, uint32_t len);
>  void ast_io_init(void);
>  bool ast_is_ahb_lpc_pnor(void);
>  bool ast_is_mbox_pnor(void);
> +bool ast_scratch_reg_is_mbox(void);
>
>  /* UART configuration */
>
> diff --git a/platforms/astbmc/common.c b/platforms/astbmc/common.c
> index 243ad9461239..9cf679161e7a 100644
> --- a/platforms/astbmc/common.c
> +++ b/platforms/astbmc/common.c
> @@ -207,8 +207,9 @@ static void astbmc_fixup_dt_mbox(struct dt_node *lpc)
>         struct dt_node *mbox;
>         char namebuf[32];
>
> -       /* All P9 machines have this and no earlier machines do */
> -       if (proc_gen != proc_gen_p9)
> +       /* All P9 machines use mbox. P8 machines can indicate they support
> +        * it using the scratch register */
> +       if (proc_gen != proc_gen_p9 && !ast_scratch_reg_is_mbox())
>                 return;
>
>         /* First check if the mbox interface is already there */
> --
> 2.15.1
>