On Sat, 2015-11-21 at 15:29 -0800, York Sun wrote: > > On 11/21/2015 02:55 PM, York Sun wrote: > > Roy, > > > > Do you remember the reason why we use different virtual memory address > > from pci > > bus address with 36-bit? For example > > > > include/configs/P1022DS.h-496-#define CONFIG_SYS_PCIE1_MEM_VIRT 0xc0000000 > > include/configs/P1022DS.h-497-#ifdef CONFIG_PHYS_64BIT > > include/configs/P1022DS.h:498:#define CONFIG_SYS_PCIE1_MEM_BUS 0xe0000000 > > include/configs/P1022DS.h-499-#define CONFIG_SYS_PCIE1_MEM_PHYS > > 0xc40000000ull > > include/configs/P1022DS.h-500-#else > > include/configs/P1022DS.h:501:#define CONFIG_SYS_PCIE1_MEM_BUS 0xc0000000 > > include/configs/P1022DS.h-502-#define CONFIG_SYS_PCIE1_MEM_PHYS 0xc0000000 > > include/configs/P1022DS.h-503-#endif > > > > As far as I can tell, the following is the mapping > > > > TLB: MEM_VIRT=>MEM_PHYS > > PCI: MEM_BUS=>MEM_PHYS > > LAW: MEM_PHYS=>pcie interface > > > > Being different for MEM_VIRT and MEM_BUS cause confusion. When I run "pci > > header" command to show the BARs, I expect I can use "md" to access the > > BAR > > address. That's not the case if MEM_BUS is different from MEM_VIRT. > > > > I forget why we did this for 36-bit addressing. The MEM_VIRT is the same > > as > > MEM_BUS for 32-bit addressing. And why do we use the same MEM_BUS address > > for > > all PCIe hose? I know they are not conflicting, but is it necessary? > > (I hope Becky and Kumar still follow this mailing list) > > I dug out an old commit 4c78d4a6c01621721b732418e1c6da684a56bbb1 by Becky > Bruce. > She believed overlapping the bus address for PCI controllers leaves more > space. > That's true. But we haven't use more than 512MB in u-boot. If we do need > more > space, we can easily move things around if we have PHYS_64BIT. If no > objection, > I'd like to change this back.
I object. It's not about how much RAM is used in U-Boot; it's about how much memory the OS needs to bounce-buffer for DMA. The addresses set up by U-Boot should match what's in the device tree. Yes, on 85xx Linux reprograms the ATMU based on the device tree rather than trusting U-Boot, but that doesn't mean every OS does. -Scott _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
