[Skiboot] [RFC PATCH 6/7] VAS: Define OPAL_VAS_READ_FIR interface

[Alistair Popple]

On Fri, 11 Nov 2016 08:56:54 AM Sukadev Bhattiprolu wrote:
> Implement the OPAL_VAS_READ_FIR interface to read a Fault Isolation
> Register (FIR) in VAS. Linux kernel can use this interface to dump these
> registers in case of a fault from VAS.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> ---
>  core/vas.c         |   38 ++++++++++++++++++++++++++++++++++++++
>  include/opal-api.h |    3 ++-
>  2 files changed, 40 insertions(+), 1 deletions(-)
> 
> diff --git a/core/vas.c b/core/vas.c
> index a4c5948..e7079bb 100644
> --- a/core/vas.c
> +++ b/core/vas.c
> @@ -18,6 +18,13 @@
>  #include <xscom.h>
>  #include <vas.h>
>  
> +#undef VAS_VERBOSE_DEBUG
> +#ifdef VAS_VERBOSE_DEBUG
> +#define vas_vdbg(__x,__fmt,...)	prlog(PR_DEBUG,"VAS: " __fmt, ##__VA_ARGS)
> +#else
> +#define vas_vdbg(__x,__fmt,...)	do { } while (0)
> +#endif
> +
>  /*
>   * TODO: Set to 64K after initial development.
>   */
> @@ -80,6 +87,37 @@ __attrconst uint64_t vas_get_wcbs_bar(int chipid)
>  	return wcbs;
>  }
>  
> +/*
> + * Read the Fault Isolation Register (FIR) identified by @idx for chip
> + * @chip_id.
> + */
> +static int opal_vas_read_fir(uint32_t chip_id, int idx, uint64_t *val)
> +{
> +	struct proc_chip *chip;
> +	uint64_t reg;
> +
> +	chip = get_chip(chip_id);
> +	if (!chip)
> +		return OPAL_PARAMETER;
> +
> +	/* FIRs 1,2,4,5 are write-only, just return 0 in them. */
> +	switch (idx) {
> +		default: /* fall through to 0 */

Why fall through and not return OPAL_PARAMETER instead? Falling through makes
it difficult to add other register indexes in future and have the caller detect
this.

> +		case 0:	reg = VAS_FIR0; break;
> +		case 3:	reg = VAS_FIR3; break;
> +		case 6:	reg = VAS_FIR6; break;
> +		case 7:	reg = VAS_FIR7; break;
> +
> +		case 1:
> +		case 2:
> +		case 4:
> +		case 5: *val = 0ULL; return OPAL_SUCCESS;
> +	}
> +
> +	return vas_scom_read(chip, reg, val);
> +}
> +opal_call(OPAL_VAS_READ_FIR, opal_vas_read_fir, 3);
> +
>  static int init_north_ctl(struct proc_chip *chip)
>  {
>  	uint64_t val = 0ULL;
> diff --git a/include/opal-api.h b/include/opal-api.h
> index 05ff51d..9705ebd 100644
> --- a/include/opal-api.h
> +++ b/include/opal-api.h
> @@ -181,7 +181,8 @@
>  #define OPAL_INT_SET_MFRR			125
>  #define OPAL_PCI_TCE_KILL			126
>  #define OPAL_NMMU_SET_PTCR			127
> -#define OPAL_LAST				127
> +#define OPAL_VAS_READ_FIR			128
> +#define OPAL_LAST				128
>  
>  /* Device tree flags */
>  
>