[Intel-gfx] [PATCH] drm/i915/hwmon: Silence "mailbox access failed" warning in snb_pcode_read

[Gupta, Anshuman]

> -----Original Message-----
> From: Dixit, Ashutosh <ashutosh.dixit at intel.com>
> Sent: Saturday, December 3, 2022 8:45 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: Gupta, Anshuman <anshuman.gupta at intel.com>; Nilawar, Badal
> <badal.nilawar at intel.com>
> Subject: [PATCH] drm/i915/hwmon: Silence "mailbox access failed" warning
> in snb_pcode_read
> 
> hwm_pcode_read_i1 is called during i915 load. This results in the following
> warning from snb_pcode_read because
> POWER_SETUP_SUBCOMMAND_READ_I1 is unsupported on DG1/DG2.
> 
> [drm:snb_pcode_read [i915]] warning: pcode (read from mbox 47c) \
> 				mailbox access failed for snb_pcode_read_p
> [i915]: -6
> 
> The code handles the unsupported command but the warning in dmesg is a
> red herring which has resulted in a couple of bugs being filed. Therefore
> silence the warning by avoiding calling snb_pcode_read_p for DG1/DG2.
> 
> Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_hwmon.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_hwmon.c
> b/drivers/gpu/drm/i915/i915_hwmon.c
> index c588a17f97e98..cca7a4350ec8f 100644
> --- a/drivers/gpu/drm/i915/i915_hwmon.c
> +++ b/drivers/gpu/drm/i915/i915_hwmon.c
> @@ -293,6 +293,10 @@ static const struct hwmon_channel_info
> *hwm_gt_info[] = {
>  /* I1 is exposed as power_crit or as curr_crit depending on bit 31 */  static int
> hwm_pcode_read_i1(struct drm_i915_private *i915, u32 *uval)  {
> +	/* Avoid ILLEGAL_SUBCOMMAND "mailbox access failed" warning in
> snb_pcode_read */
> +	if (IS_DG1(i915) || IS_DG2(i915))
> +		return -ENXIO;
AFAIK it is specific to client specific parts, how about declaring a is_client intel_runtime_info flag to
distinguish between client and server part. That will also cover  any future platform as well.  

BR ,
Anshuman 
> +
>  	return snb_pcode_read_p(&i915->uncore, PCODE_POWER_SETUP,
>  				POWER_SETUP_SUBCOMMAND_READ_I1, 0,
> uval);  }
> --
> 2.38.0