Re: [PATCH v3 5/5] drm/i915: Setup static bias for GPU

Ville Syrjälä
2015-03-30T09:56:26Z

On Sat, Mar 28, 2015 at 03:23:38PM +0530, deepak.s@linux.intel.com wrote:
> From: Deepak S <deepak.s@linux.intel.com>
>
> Based on the spec, Setting up static BIAS for GPU to improve the
> rps performace.

My understanding is that this would only improve the GPU performance
under TDP constrained use cases, at the cost of CPU performance. So
it's not some magic bullet that makes things just faster (tm).

>
> Signed-off-by: Deepak S <deepak.s@linux.intel.com>
> ---
> drivers/gpu/drm/i915/i915_reg.h | 5 +++++
> drivers/gpu/drm/i915/intel_pm.c | 12 ++++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index b522eb6..ea708ba 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -670,6 +670,11 @@ enum skl_disp_power_wells {
> #define FB_FMAX_VMIN_FREQ_LO_SHIFT 27
> #define FB_FMAX_VMIN_FREQ_LO_MASK 0xf8000000
>
> +#define VLV_IOSFB_RPS_OVERRIDE 0x04
> +#define VLV_OVERRIDE_RPS_MASK 1
> +#define VLV_ENABLE_BIAS_SHARE (1 << 1)
> +#define VLV_BIAS_VAL (6 << 2)

Can we use better names for these (from configdb, say)?

> +
> #define VLV_CZ_CLOCK_TO_MILLI_SEC 100000
> #define VLV_RP_UP_EI_THRESHOLD 90
> #define VLV_RP_DOWN_EI_THRESHOLD 70
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 88e71a3..673612b 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -5015,6 +5015,12 @@ static void cherryview_enable_rps(struct drm_device *dev)
> GEN6_RP_UP_BUSY_AVG |
> GEN6_RP_DOWN_IDLE_AVG);
>
> + /* Setting Fixed Bias */
> + val = VLV_OVERRIDE_RPS_MASK |
> + VLV_ENABLE_BIAS_SHARE |
> + VLV_BIAS_VAL;
> + vlv_punit_write(dev_priv, VLV_IOSFB_RPS_OVERRIDE, val);
> +
> val = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
>
> /* RPS code assumes GPLL is used */
> @@ -5099,6 +5105,12 @@ static void valleyview_enable_rps(struct drm_device *dev)
>
> I915_WRITE(GEN6_RC_CONTROL, rc6_mode);
>
> + /* Setting Fixed Bias */
> + val = VLV_OVERRIDE_RPS_MASK |
> + VLV_ENABLE_BIAS_SHARE |
> + VLV_BIAS_VAL;
> + vlv_punit_write(dev_priv, VLV_IOSFB_RPS_OVERRIDE, val);
> +
> val = vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS);
>
> /* RPS code assumes GPLL is used */
> --
> 1.9.1

--
Ville Syrjälä
Intel OTC