On Wed, 26 Sep 2012 10:34:01 -0700
Ben Widawsky <ben at bwidawsk.net> wrote:
> BIOS should be setting the minimum voltage for rc6 to be 450mV. Old or
> buggy BIOSen may not be doing this, so we correct it for them. Ideally
> customers should update the BIOS as only it would know the optimal
> values for the platform, so we leave that fact as a DRM_ERROR for the
> user to see.
>
> Unfortunately this isn't fixing any of the issues it was targeted to
> fix, but it is documented that we must do it.
>
> CC: Jesse Barnes <jbarnes at virtuousgeek.org>
> CC: Matt Turner <mattst88 at gmail.com>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 4 ++++
> drivers/gpu/drm/i915/intel_pm.c | 18 ++++++++++++++++--
> 2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index a828e90..13aafa5 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -4213,6 +4213,10 @@
> #define GEN6_READ_OC_PARAMS 0xc
> #define GEN6_PCODE_WRITE_MIN_FREQ_TABLE 0x8
> #define GEN6_PCODE_READ_MIN_FREQ_TABLE 0x9
> +#define GEN6_PCODE_WRITE_RC6VIDS 0x4
> +#define GEN6_PCODE_READ_RC6VIDS 0x5
> +#define GEN6_ENCODE_RC6_VID(mv) (((mv) / 5) - 245) < 0 ?: 0
> +#define GEN6_DECODE_RC6_VID(vids) (((vids) * 5) > 0 ? ((vids) * 5) + 245 : 0)
> #define GEN6_PCODE_DATA 0x138128
> #define GEN6_PCODE_FREQ_IA_RATIO_SHIFT 8
>
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 6488cd0..9a6edf0 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -2404,10 +2404,10 @@ static void gen6_enable_rps(struct drm_device *dev)
> struct intel_ring_buffer *ring;
> u32 rp_state_cap;
> u32 gt_perf_status;
> - u32 pcu_mbox, rc6_mask = 0;
> + u32 rc6vids, pcu_mbox, rc6_mask = 0;
> u32 gtfifodbg;
> int rc6_mode;
> - int i;
> + int i, ret;
>
> WARN_ON(!mutex_is_locked(&dev->struct_mutex));
>
> @@ -2526,6 +2526,20 @@ static void gen6_enable_rps(struct drm_device *dev)
> /* enable all PM interrupts */
> I915_WRITE(GEN6_PMINTRMSK, 0);
>
> + rc6vids = 0;
> + ret = sandybridge_pcode_read(dev_priv, GEN6_PCODE_READ_RC6VIDS, &rc6vids);
> + if (IS_GEN6(dev) && ret) {
> + DRM_DEBUG_DRIVER("Couldn't check for BIOS workaround\n");
> + } else if (IS_GEN6(dev) && (GEN6_DECODE_RC6_VID(rc6vids & 0xff) < 450)) {
> + DRM_ERROR("You should update your BIOS. Correcting minimum rc6 voltage (%dmV->%dmV)\n",
> + GEN6_DECODE_RC6_VID(rc6vids & 0xff), 450);
> + rc6vids &= 0xffff00;
> + rc6vids |= GEN6_ENCODE_RC6_VID(450);
> + ret = sandybridge_pcode_write(dev_priv, GEN6_PCODE_WRITE_RC6VIDS, rc6vids);
> + if (ret)
> + DRM_ERROR("Couldn't fix incorrect rc6 voltage\n");
> + }
> +
> gen6_gt_force_wake_put(dev_priv);
> }
>
Reviewed-by: Jesse Barnes <jbarnes at virtuousgeek.org>
--
Jesse Barnes, Intel Open Source Technology Center
