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

["Kumar, Shobhit" <shobhit.kumar@linux.intel.com>]

On 01/15/2016 07:14 AM, Matt Roper wrote:
> 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@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.
>

Yeah will do that.

> 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.
>

Perhaps we can but that will take some time. I will add paranoid parsing 
as done in edac with minimal #defined offsets for now. Think that should 
suffice. At next level we can work on exporting new functionality from 
the DMI files.

Regards
Shobhit

>
> 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
>>
>
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