On Thu, Aug 11, 2016 at 03:54:30PM -0400, Lyude wrote:
> In order to add proper support for the SAGV, we need to be able to know
> what the cause of a failure to change the SAGV through the pcode mailbox
> was. The reasoning for this is that some very early pre-release Skylake
> machines don't actually allow you to control the SAGV on them, and
> indicate an invalid mailbox command was sent.
>
> This also might come in handy in the future for debugging.
>
> Signed-off-by: Lyude <cpaul at redhat.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Cc: stable at vger.kernel.org
> ---
> drivers/gpu/drm/i915/i915_reg.h | 1 +
> drivers/gpu/drm/i915/intel_pm.c | 10 ++++++++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index da82744..73b3d4d 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7121,6 +7121,7 @@ enum {
> #define VLV_MEDIA_C0_COUNT _MMIO(0x13811C)
>
> #define GEN6_PCODE_MAILBOX _MMIO(0x138124)
> +#define GEN6_PCODE_INVALID_CMD (1<<0)
It doesn't work quite like that. Instead the low 8 bits will contian
the error code, iff pcode has cleared the "READY" bit:
snb-ivb docs say:
00h MAILBOX_GTDRIVER_CC_SUCCESS
01h MAILBOX_GTDRIVER_CC_ILLEGAL_CMD
02h MAILBOX_GTDRIVER_CC_MIN_FREQUENCY_TABLE_GT_RATIO_OUT_OF_RANGE
03h MAILBOX_GTDRIVER_CC_TIMEOUT
FFh MAILBOX_GTDRIVER_CC_UNIMPLEMENTED_CMD
hsw-bdw docs say:
00h SUCCESS
01h ILLEGAL_CMD
02h TIMEOUT
03h ILLEGAL_DATA
10h MIN_FREQUENCY_TABLE_GT_RATIO_OUT_OF_RANGE
skl docs say:
00h SUCCESS
01h ILLEGAL_CMD
02h TIMEOUT
03h ILLEGAL_DATA
So looks like 02h and 03h will need to be interpreted in two different
ways depending on the platform. Assuming we want to decode the error
into a a human readable form for dmesg.
> #define GEN6_PCODE_READY (1<<31)
> #define GEN6_PCODE_WRITE_RC6VIDS 0x4
> #define GEN6_PCODE_READ_RC6VIDS 0x5
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 99014d7..8752730 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -7674,6 +7674,11 @@ int sandybridge_pcode_read(struct drm_i915_private
> *dev_priv, u32 mbox, u32 *val
> *val = I915_READ_FW(GEN6_PCODE_DATA);
> I915_WRITE_FW(GEN6_PCODE_DATA, 0);
>
> + if (I915_READ_FW(GEN6_PCODE_MAILBOX) & GEN6_PCODE_INVALID_CMD) {
> + DRM_DEBUG_DRIVER("warning: pcode (read) mailbox access
> indicated invalid command\n");
> + return -EINVAL;
> + }
> +
> return 0;
> }
>
> @@ -7704,6 +7709,11 @@ int sandybridge_pcode_write(struct drm_i915_private
> *dev_priv,
>
> I915_WRITE_FW(GEN6_PCODE_DATA, 0);
>
> + if (I915_READ_FW(GEN6_PCODE_MAILBOX) & GEN6_PCODE_INVALID_CMD) {
> + DRM_DEBUG_DRIVER("warning: pcode (write) mailbox access
> indicated invalid command\n");
> + return -EINVAL;
> + }
> +
> return 0;
> }
>
> --
> 2.7.4
--
Ville Syrjälä
Intel OTC
