Re: [PATCH 01/14] x86, ACPI, mm: Kill max_low_pfn_mapped

From: Yinghai Lu
Date: Fri Mar 08 2013 - 00:23:09 EST


On Thu, Mar 7, 2013 at 9:10 PM, Tejun Heo <tj@xxxxxxxxxx> wrote:
> On Thu, Mar 07, 2013 at 08:58:27PM -0800, Yinghai Lu wrote:
>> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
>> index 69d97cb..7f9380b 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
>> @@ -81,7 +81,7 @@ static unsigned long i915_stolen_to_physical(struct drm_device *dev)
>> base -= dev_priv->mm.gtt->stolen_size;
>> } else {
>> /* Stolen is immediately above Top of Memory */
>> - base = max_low_pfn_mapped << PAGE_SHIFT;
>> + base = __REMOVED_CRAZY__ << PAGE_SHIFT;
>
> Huh?

Whole function:

static unsigned long i915_stolen_to_physical(struct drm_device *dev)
{
struct drm_i915_private *dev_priv = dev->dev_private;
struct pci_dev *pdev = dev_priv->bridge_dev;
u32 base;

/* On the machines I have tested the Graphics Base of Stolen Memory
* is unreliable, so on those compute the base by subtracting the
* stolen memory from the Top of Low Usable DRAM which is where the
* BIOS places the graphics stolen memory.
*
* On gen2, the layout is slightly different with the Graphics Segment
* immediately following Top of Memory (or Top of Usable DRAM). Note
* it appears that TOUD is only reported by 865g, so we just use the
* top of memory as determined by the e820 probe.
*
* XXX gen2 requires an unavailable symbol and 945gm fails with
* its value of TOLUD.
*/
base = 0;
if (INTEL_INFO(dev)->gen >= 6) {
/* Read Base Data of Stolen Memory Register (BDSM) directly.
* Note that there is also a MCHBAR miror at 0x1080c0 or
* we could use device 2:0x5c instead.
*/
pci_read_config_dword(pdev, 0xB0, &base);
base &= ~4095; /* lower bits used for locking register */
} else if (INTEL_INFO(dev)->gen > 3 || IS_G33(dev)) {
/* Read Graphics Base of Stolen Memory directly */
pci_read_config_dword(pdev, 0xA4, &base);
#if 0
} else if (IS_GEN3(dev)) {
u8 val;
/* Stolen is immediately below Top of Low Usable DRAM */
pci_read_config_byte(pdev, 0x9c, &val);
base = val >> 3 << 27;
base -= dev_priv->mm.gtt->stolen_size;
} else {
/* Stolen is immediately above Top of Memory */
base = __REMOVED_CRAZY__ << PAGE_SHIFT;
#endif
}

return base;
}
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