[Intel-gfx] [PATCH 6/7] drm/i915: Add support to parse DMI table and get platform memory info

[Matt Roper]

On Thu, Jan 14, 2016 at 05:32:47PM +0530, Shobhit Kumar wrote:
> This is needed for WM computation workaround for arbitrated display
> bandwidth.
> 
> Signed-off-by: Shobhit Kumar <shobhit.kumar at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_dma.c | 19 +++++++++++++++++++
>  drivers/gpu/drm/i915/i915_drv.h |  6 ++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index a0f5659..03c3131 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -49,6 +49,7 @@
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/oom.h>
> +#include <linux/dmi.h>
>  
>  
>  static int i915_getparam(struct drm_device *dev, void *data,
> @@ -855,6 +856,21 @@ static void intel_init_dpio(struct drm_i915_private *dev_priv)
>  	}
>  }
>  
> +static void dmi_decode_memory_info(const struct dmi_header *hdr, void *priv)
> +{
> +	struct drm_i915_private *dev_priv = (struct drm_i915_private *) priv;
> +	const u8 *data = (const u8 *) hdr;
> +
> +	if (hdr->type == 17 && hdr->length > 0x17) {

I think there are some constants in include/linux/dmi.h that we can use
instead of magic numbers.  DMI_ENTRY_MEM_DEVICE.

I'm not familiar with any of this DMI stuff; it seems like there are
functions elsewhere in the kernel (e.g., decode_dclk() in
drivers/edac/i7core_edac.c) that decode this into a memdev_dmi_entry and
then do some more robust/paranoid checking to determine the actual
speed.  Unfortunately it's static to that file and not directly callable
by us.

I wonder if it would make sense to refactor that structure and decoding
out into the general DMI files and export them for module use so that we
could just call those functions.


Matt

> +
> +		/* Found a memory channel */
> +		dev_priv->dmi.mem_channel++;
> +
> +		/* Get the speed */
> +		dev_priv->dmi.mem_speed = (uint16_t) (*((uint16_t *)(data + 0x15)));
> +	}
> +}
> +
>  /**
>   * i915_driver_load - setup chip and create an initial config
>   * @dev: DRM device
> @@ -882,6 +898,9 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
>  	dev->dev_private = dev_priv;
>  	dev_priv->dev = dev;
>  
> +	/* walk the dmi device table for getting platform memory information */
> +	dmi_walk(dmi_decode_memory_info, (void *) dev_priv);
> +
>  	/* Setup the write-once "constant" device info */
>  	device_info = (struct intel_device_info *)&dev_priv->info;
>  	memcpy(device_info, info, sizeof(dev_priv->info));
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 104bd18..f588993 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1962,6 +1962,12 @@ struct drm_i915_private {
>  	 * NOTE: This is the dri1/ums dungeon, don't add stuff here. Your patch
>  	 * will be rejected. Instead look for a better place.
>  	 */
> +
> +	/* DMI data for memory bandwidth calculation */
> +	struct {
> +		uint16_t mem_channel;
> +		uint16_t mem_speed;
> +	} dmi;
>  };
>  
>  static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
> -- 
> 2.4.3
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795