linux-kernel - Re: [PATCH 01/14] x86, ACPI, mm: Kill max_low_pfn

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Date:	Thu, 7 Mar 2013 21:22:57 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Renninger <trenn@...e.de>,
	Tang Chen <tangchen@...fujitsu.com>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>,
	Jacob Shin <jacob.shin@....com>, linux-acpi@...r.kernel.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 01/14] x86, ACPI, mm: Kill max_low_pfn_mapped

On Thu, Mar 7, 2013 at 9:10 PM, Tejun Heo <tj@...nel.org> 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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