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intel/i945/gma: Place GTT below top of memory 

Since commit 17fec8a0 [1]

	drm/i915: Use Graphics Base of Stolen Memory on all gen3+

present in the Linux kernel since version 3.12, 3D does not work
anymore [2].

Comparing the graphics registers, in this case that means output of
`intel_reg_dumper`, the vendor Video BIOS is setting the register
PGTBL_CTL/PGETBL_CTL, only documented in the i965 datasheet [3], to
`0x3ffc0001` on a system with 1 GB of RAM, while native graphics init
sets it to `0x3f800001`.

Currently native graphis init sets the GTT right above the base
address of stolen memory. The Video BIOS sets it below the top of
memory.  The Linux Intel driver expects it to be below top of memory, so
do it this way, by setting the address to TOM minus the size of the GTT,
which is hardcoded to 256 KiB.

As `PGETBL_CTL` is zero by default, reading its value in the beginning
is not necessary and is only confusing. Make it clear that the code
calculates the value.

There is still a PTE error reported during boot, but 3D works
with Linux 3.12+ and no user visible problems are shown.

[1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17fec8a08698bcab98788e1e89f5b8e7502ababd
[2] https://bugs.freedesktop.org/show_bug.cgi?id=79038
[3] https://01.org/linuxgraphics/sites/default/files/documentation/965_g35_vol_1_graphics_core_0.pdf
    Intel ® 965 Express Chipset Family and
      Intel ® G35 Express Chipset Graphics Controller
      Programmer’s Reference Manual
    Volume 1: Graphics Core
    Revision 1.0a

Change-Id: I0a5b04c2c5300f5056cb48075aa5804984bc9948
Signed-off-by: Paul Menzel <paulepanter@users.sourceforge.net>
Signed-off-by: Francis Rowe <info@gluglug.org.uk>
Reviewed-on: http://review.coreboot.org/5927
Tested-by: build bot (Jenkins)
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
This commit is contained in:
Paul Menzel 2014-06-05 22:45:35 +02:00 committed by Vladimir Serbinenko
parent d609e89adf
commit cc95f18973
1 changed files with 11 additions and 3 deletions
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14
src/northbridge/intel/i945/gma.c
View File

@ -52,11 +52,19 @@
static int gtt_setup(unsigned int mmiobase)
{
unsigned long PGETBL_save;
unsigned long tom; // top of memory
PGETBL_save = read32(mmiobase + PGETBL_CTL) & ~PGETBL_ENABLED;
/*
* The Video BIOS places the GTT right below top of memory.
*
* It is not documented in the Intel 945 datasheet, but the Intel
* developers said that it is normally placed there.
*
* TODO: Add option to make the GTT size runtime configurable
*/
tom = pci_read_config8(dev_find_slot(0, PCI_DEVFN(0, 0)), TOLUD) << 24;
PGETBL_save = tom - 256 * KiB;
PGETBL_save |= PGETBL_ENABLED;
PGETBL_save |= pci_read_config32(dev_find_slot(0, PCI_DEVFN(2,0)), 0x5c) & 0xfffff000;
PGETBL_save |= 2; /* set GTT to 256kb */
write32(mmiobase + GFX_FLSH_CNTL, 0);