Re: [PATCH 7/7] drm/i915: expose energy counter on SNB and IVB

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Sep 06, 2012 at 01:54:10PM -0700, Ben Widawsky wrote:
> From: Jesse Barnes <jbarnes@virtuousgeek.org>
> 
> On SNB and IVB, there's an MSR (also exposed through MCHBAR) we can use
> to read out the amount of energy used over time.  Expose this in sysfs
> to make it easy to do power comparisons with different configurations.
> 
> If the platform supports it, the file will show up under the
> drm/card0/power subdirectory of the PCI device in sysfs as gt_energy_uJ.
> The value in the file is a running total of energy (in microjoules)
> consumed by the graphics device.
> 
> v2: move to sysfs (Ben, Daniel)
>     expose a simple value (Chris)
>     drop unrelated hunk (Ben)
> 
> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> 
> v3: by Ben
> Tied it into existing rc6  sysfs entries and named that a more generic
> "power attrs." Fixed rebase conflicts.
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
>  drivers/gpu/drm/i915/i915_reg.h   |  2 ++
>  drivers/gpu/drm/i915/i915_sysfs.c | 25 +++++++++++++++++++++++--
>  2 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index d0b60f2..0e34f5f 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1242,6 +1242,8 @@
>  #define CLKCFG_MEM_800					(3 << 4)
>  #define CLKCFG_MEM_MASK					(7 << 4)
>  
> +#define SECP_NRG_STTS			(MCHBAR_MIRROR_BASE_SNB + 0x592c)
> +
>  #define TSC1			0x11001
>  #define   TSE			(1<<0)
>  #define TR1			0x11006
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index e3a31ae..6bbc9af 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -76,22 +76,43 @@ show_rc6pp_ms(struct device *kdev, struct device_attribute *attr, char *buf)
>  	return snprintf(buf, PAGE_SIZE, "%u", rc6pp_residency);
>  }
>  
> +#define MSR_IA32_PACKAGE_POWER_SKU_UNIT		0x00000606
> +
> +static ssize_t
> +show_gt_energy_uJ(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> +	struct drm_i915_private *dev_priv = dminor->dev->dev_private;
> +	u64 ppsu;
> +	u32 val, units;
> +
> +	rdmsrl(MSR_IA32_PACKAGE_POWER_SKU_UNIT, ppsu);
> +
> +	ppsu = (ppsu & 0x1f00) >> 8;
> +	units = 1000000 / (1 << ppsu); /* convert to uJ */
> +	val = I915_READ(SECP_NRG_STTS);
> +
> +	return snprintf(buf, PAGE_SIZE, "%u", val * units);

Besides that this could overflow it also introduces rounding errors that
accumulate. I guess we need a 64 mul+div here, like in the residency
counters.
-Daniel

> +}
> +
>  static DEVICE_ATTR(rc6_enable, S_IRUGO, show_rc6_mask, NULL);
>  static DEVICE_ATTR(rc6_residency_ms, S_IRUGO, show_rc6_ms, NULL);
>  static DEVICE_ATTR(rc6p_residency_ms, S_IRUGO, show_rc6p_ms, NULL);
>  static DEVICE_ATTR(rc6pp_residency_ms, S_IRUGO, show_rc6pp_ms, NULL);
> +static DEVICE_ATTR(gt_energy_uJ, S_IRUGO, show_gt_energy_uJ, NULL);
>  
> -static struct attribute *rc6_attrs[] = {
> +static struct attribute *power_attrs[] = {
>  	&dev_attr_rc6_enable.attr,
>  	&dev_attr_rc6_residency_ms.attr,
>  	&dev_attr_rc6p_residency_ms.attr,
>  	&dev_attr_rc6pp_residency_ms.attr,
> +	&dev_attr_gt_energy_uJ.attr,
>  	NULL
>  };
>  
>  static struct attribute_group rc6_attr_group = {
>  	.name = power_group_name,
> -	.attrs =  rc6_attrs
> +	.attrs =  power_attrs
>  };
>  #endif
>  
> -- 
> 1.7.12
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch