[Intel-gfx] [PATCH 7/8] drm/i915: Add support to parse DMI table and get platform memory info (v3)

[Matt Roper]

From: Shobhit Kumar <shobhit.kumar at intel.com>

This is needed for WM computation workaround for arbitrated display
bandwidth.

v2: Address Matt's review comments
    - Be more paranoid while dmi decoding
    - Also add support for decoding speed from configured memory speed
      if availble in DMI memory entry

v3 (by Matt):
 - Use memdev_dmi_entry from dmi.h
 - Don't try to use/compare negative numbers in unsigned types

Cc: matthew.d.roper at intel.com
Signed-off-by: Shobhit Kumar <shobhit.kumar at intel.com>
Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c | 34 ++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_drv.h |  7 +++++++
 2 files changed, 41 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 4aa3db6..4259afe 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,
@@ -973,6 +974,33 @@ static void i915_mmio_cleanup(struct drm_device *dev)
 	pci_iounmap(dev->pdev, dev_priv->regs);
 }
 
+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 struct memdev_dmi_entry *memdev =
+		(const struct memdev_dmi_entry *)hdr;
+	uint16_t mem_speed = 0;
+
+	if (hdr->type != DMI_ENTRY_MEM_DEVICE)
+		return;
+
+	/* Get the speed */
+	if (hdr->length > offsetof(struct memdev_dmi_entry, conf_mem_clk_speed))
+		mem_speed = memdev->conf_mem_clk_speed;
+	else if (hdr->length > offsetof(struct memdev_dmi_entry, speed))
+		mem_speed = memdev->speed;
+	else
+		return;
+
+	dev_priv->dmi.mem_channel++;
+
+	/* All channels are expected to have same the speed */
+	if (dev_priv->dmi.mem_speed == 0)
+		dev_priv->dmi.mem_speed = mem_speed;
+	else if (mem_speed != dev_priv->dmi.mem_speed)
+		dev_priv->dmi.valid = false;
+}
+
 /**
  * i915_driver_load - setup chip and create an initial config
  * @dev: DRM device
@@ -1000,6 +1028,12 @@ 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 */
+	dev_priv->dmi.valid = true;
+	dmi_walk(dmi_decode_memory_info, dev_priv);
+	if (!dev_priv->dmi.mem_speed)
+		dev_priv->dmi.valid = false;
+
 	/* 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 f37ac12..a2a7d8d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2022,6 +2022,13 @@ 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 {
+		bool valid;
+		uint16_t mem_channel;
+		int16_t mem_speed;
+	} dmi;
 };
 
 static inline struct drm_i915_private *to_i915(const struct drm_device *dev)
-- 
2.1.4