[Intel-gfx] [Intel 945] BSM: How to determine size of DRAM used for internal graphics?
Dear Intel graphics folks, since commit 17fec8a0 [1] drm/i915: Use Graphics Base of Stolen Memory on all gen3+ Linux reads the register BSM (Base of Stolen Memory) directly to get the base address of graphics stolen memory. With coreboot [2] and native graphics init – note that everything works with the proprietary VGA BIOS/Option ROM – this causes a regression [3] as this register is not programmed at all. From the datasheet *Mobile Intel® 945 Express Chipset Family* [4] the register BSM is described on page 290. Graphics Stolen Memory and TSEG are within DRAM space defined under TOLUD. From the top of low used DRAM, (G)MCH claims 1 to 64 MBs of DRAM for internal graphics if enabled. This register contains bits 31 to 20 of the base address of stolen DRAM memory. The host interface determines the base of graphics stolen memory by subtracting the graphics stolen memory size from TOLUD. See Device 0 TOLUD for more explanations. Also see Figure 12 *Main Memory Address Range* in section 9.2 on page 325. Unfortunately I am unable to find out how the graphics stolen memory size is determined. I’d have thought it is used for the framebuffer, but according to page 93 (Graphics Mode select (GMS)) that the framebuffer size can only be 1 MB or 8 MB, which contradicts that it can be up to 64 MB. If it is determined implicitly by the value I set the BSM to, where can I find the recommendations what size to use? I’d guess it is dependent on the RAM size, that means dependent if the system has 512 MB or 4 GB for example. Thanks, Paul [1] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17fec8a08698bcab98788e1e89f5b8e7502ababd [2] http://www.coreboot.org/ [3] https://bugs.freedesktop.org/show_bug.cgi?id=79038 [4] http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/mobile-945-express-chipset-datasheet.pdf Document Number: 309219-006 signature.asc Description: This is a digitally signed message part ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [Intel 945] BSM: How to determine size of DRAM used for internal graphics?
Dear Intel graphics folks, Am Freitag, den 30.05.2014, 13:45 +0200 schrieb Paul Menzel: > since commit 17fec8a0 [1] > > drm/i915: Use Graphics Base of Stolen Memory on all gen3+ > > Linux reads the register BSM (Base of Stolen Memory) directly to get the > base address of graphics stolen memory. With coreboot [2] and native > graphics init – note that everything works with the proprietary VGA > BIOS/Option ROM – this causes a regression [3] as this register is not > programmed at all. > > From the datasheet *Mobile Intel® 945 Express Chipset Family* [4] the > register BSM is described on page 290. > > Graphics Stolen Memory and TSEG are within DRAM space defined > under TOLUD. From the top of low used DRAM, (G)MCH claims 1 to > 64 MBs of DRAM for internal graphics if enabled. > > This register contains bits 31 to 20 of the base address of > stolen > DRAM memory. The host interface determines the base of > graphics stolen memory by subtracting the graphics stolen > memory size from TOLUD. See Device 0 TOLUD for more > explanations. > > Also see Figure 12 *Main Memory Address Range* in section 9.2 on page > 325. > > Unfortunately I am unable to find out how the graphics stolen memory > size is determined. I’d have thought it is used for the framebuffer, but > according to page 93 (Graphics Mode select (GMS)) that the framebuffer > size can only be 1 MB or 8 MB, which contradicts that it can be up to 64 > MB. > > If it is determined implicitly by the value I set the BSM to, where can > I find the recommendations what size to use? I’d guess it is dependent > on the RAM size, that means dependent if the system has 512 MB or 4 GB > for example. The datasheet documents the bits of the register BSM as Read Only (RO). So I am even more confused now. Thanks, Paul > [1] > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17fec8a08698bcab98788e1e89f5b8e7502ababd > [2] http://www.coreboot.org/ > [3] https://bugs.freedesktop.org/show_bug.cgi?id=79038 > [4] > http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/mobile-945-express-chipset-datasheet.pdf > Document Number: 309219-006 signature.asc Description: This is a digitally signed message part ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
Re: [Intel-gfx] [Intel 945] BSM: How to determine size of DRAM used for internal graphics?
Dear Intel graphics folks, Am Freitag, den 30.05.2014, 14:47 +0200 schrieb Paul Menzel: > Am Freitag, den 30.05.2014, 13:45 +0200 schrieb Paul Menzel: > > > since commit 17fec8a0 [1] > > > > drm/i915: Use Graphics Base of Stolen Memory on all gen3+ > > > > Linux reads the register BSM (Base of Stolen Memory) directly to get the > > base address of graphics stolen memory. With coreboot [2] and native > > graphics init – note that everything works with the proprietary VGA > > BIOS/Option ROM – this causes a regression [3] as this register is not > > programmed at all. > > > > From the datasheet *Mobile Intel® 945 Express Chipset Family* [4] the > > register BSM is described on page 290. > > > > Graphics Stolen Memory and TSEG are within DRAM space defined > > under TOLUD. From the top of low used DRAM, (G)MCH claims 1 to > > 64 MBs of DRAM for internal graphics if enabled. > > > > This register contains bits 31 to 20 of the base address of > > stolen > > DRAM memory. The host interface determines the base of > > graphics stolen memory by subtracting the graphics stolen > > memory size from TOLUD. See Device 0 TOLUD for more > > explanations. > > > > Also see Figure 12 *Main Memory Address Range* in section 9.2 on page > > 325. > > > > Unfortunately I am unable to find out how the graphics stolen memory > > size is determined. I’d have thought it is used for the framebuffer, but > > according to page 93 (Graphics Mode select (GMS)) that the framebuffer > > size can only be 1 MB or 8 MB, which contradicts that it can be up to 64 > > MB. > > > > If it is determined implicitly by the value I set the BSM to, where can > > I find the recommendations what size to use? I’d guess it is dependent > > on the RAM size, that means dependent if the system has 512 MB or 4 GB > > for example. > > The datasheet documents the bits of the register BSM as Read Only (RO). > So I am even more confused now. It turned out that the register is indeed read-only and that the register to look at seems to be PGTBL_CTL/PGETBL_CTL. Thanks, Paul > > [1] > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=17fec8a08698bcab98788e1e89f5b8e7502ababd > > [2] http://www.coreboot.org/ > > [3] https://bugs.freedesktop.org/show_bug.cgi?id=79038 > > [4] > > http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/mobile-945-express-chipset-datasheet.pdf > > Document Number: 309219-006 signature.asc Description: This is a digitally signed message part ___ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
