On Tue, Dec 18, 2018 at 05:19:24PM +0800, Jianjun Wang wrote: > On Mon, 2018-12-17 at 15:46 +0000, Lorenzo Pieralisi wrote: > > On Mon, Dec 17, 2018 at 08:32:47AM -0600, Bjorn Helgaas wrote: > > > On Mon, Dec 17, 2018 at 04:19:39PM +0800, Jianjun Wang wrote: > > > > On Thu, 2018-12-13 at 08:55 -0600, Bjorn Helgaas wrote: > > > > > On Thu, Dec 06, 2018 at 09:09:13AM +0800, Jianjun Wang wrote: > > > > > > The read value of BAR0 is 0xffff_ffff, it's size will be calculated as 4GB > > > > > > in arm64 but bogus alignment values at arm32, the pcie device and devices > > > > > > behind this bridge will not be enabled. Fix it's BAR0 resource size to > > > > > > guarantee the pcie devices will be enabled correctly. > > > > > > > > > > So this is a hardware erratum? Per spec, a memory BAR has bit 0 hardwired > > > > > to 0, and an IO BAR has bit 1 hardwired to 0. > > > > > > > > Yes, it only works properly on 64bit platform. > > > > > > I don't understand. BARs are supposed to work the same regardless of > > > whether it's a 32- or 64-bit platform. If this is a workaround for a > > > hardware defect, please just say that explicitly. > > > > I do not understand this either. First thing to do is to describe the > > problem properly so that we can actually find a solution to it. > > > > Lorenzo > > This BAR0 is a 64-bit memory BAR, the HW default values for this BAR is > 0xffff_ffff_0000_0000 and it could not be changed except by config write > operation. > > The calculated BAR size will be 0 in 32-bit platform since the > phys_addr_t is a 32bit value in 32-bit platform. > > Actually MediaTek's HW does not using this BAR0, just omit it when > assign resource is totally fine. > > When assign the resource for each device, software will check the > resource alignment first, and the resource of length zero will be > regarded as a bogus alignment resource, it will be ignored and won't > claim a resource parent for it. > > When drivers try to enable the PCIe devices, the software will enable > it's resources, but it will return an error number when found a > unclaimed resource, in that case, the flow of enable devices will be > interrupted and PCIe devices won't work properly. As a starting point, please provide kernel logs for both 64-bit and 32-bit platforms (without this patch applied) and also a: cat /proc/iomem and lspci output for both configurations. Thanks, Lorenzo
