[+cc Rob, devicetree list] On Mon, Oct 23, 2017 at 11:09:50AM +0530, Vidya Sagar wrote: > On Saturday 21 October 2017 12:38 AM, Bjorn Helgaas wrote: > >On Fri, Oct 13, 2017 at 12:20:06AM +0530, Vidya Sagar wrote: > >>use only 4K space from available 1GB PCIe aperture to access > >>end points configuration space by dynamically moving AFI_AXI_BAR > >>base address and always making sure that the desired location > >>to be accessed for generating required config space access falls > >>in the 4K space reserved for this purpose. This would give more > >>space for mapping end point device's BARs on some of Tegra platforms > > > >Do you now have a revlock issue between this driver change and the > >corresponding DT changes? I.e., what happens when you run this driver > >change with an older DT that specifies a 256MB config aperture? What > >happens if you run the older driver with a new DT that only specifies > >a 4KB config aperture? > > Yes. Both driver and DT changes must go together. New driver and old DT (or) > Old driver and new DT would break config space access. This revlock sounds like a pretty major issue. I don't know if the DT conventions even allow for this. If they do, it definitely needs to be mentioned in the changelog. Looking for acks from Thierry and Rob. > >>- addr += tegra_pcie_conf_offset(devfn, where); > >>+ addr = pcie->cfg_va_base; > >>+ val = ((((u32)where & 0xf00) >> 8) << 24) | > >>+ (bus->number << 16) | (PCI_SLOT(devfn) << 11) | > >>+ (PCI_FUNC(devfn) << 8) | (where & 0xff); > >I think it would be useful to keep tegra_pcie_conf_offset() (extending > >it to take the bus number) near the comment describing the mapping. > I'll take care of it in next patch. > > > >>+ addr = (val & (SZ_4K - 1)) + addr; > >>+ val = val & ~(SZ_4K - 1); > > val &= ~(SZ_4K - 1); > > > >I *think* what you're doing is computing a config space offset and > >mapping the 4KB window that contains it. > > > >"addr" is not used at all in the AFI_AXI_BAR0 programming, so this > >would be clearer as: > > > > val = ... > > afi_writel(...) > > afi_writel(...) > > > > addr = pcie->cfg_va_base + (val & (SZ_4K - 1)); > but, addr is using the intermediate 'val' i.e. before 'val &= > ~(SZ_4K - 1)' operation is performed on it. Ah, right. I think adding another temporary variable here would make it clearer. > > } > > > > return addr; > > > >>+ afi_writel(pcie, pcie->cs->start - val, AFI_AXI_BAR0_START); > >>+ afi_writel(pcie, (val + SZ_4K) >> 12, AFI_AXI_BAR0_SZ); > >> } > >> return addr; > >>-- > >>2.7.4 > >> > -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
