On Mon, 2015-11-23 at 09:00 -0800, York Sun wrote: > > On 11/23/2015 08:24 AM, Scott Wood wrote: > > 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. > > Isn't this backward? I mean the device tree should match u-boot,
Yes, and I don't want to deal with the churn of these device trees changing. > or u-boot should fix up the device tree, right? In theory yes, but then you really are affecting Linux's usage. > I checked several device tree files in kernel. We are not using more than > 512MB > for each PCI. What's the benefit of using the same address 0xe0000000? Reducing the amount of RAM whose address matches a PCI bus address and thus can't be used for PCI DMA. -Scott _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
