On Fri, Apr 12, 2024 at 12:08:41PM -0400, Frank Li wrote: > When PERST# assert and deassert happens on the PERST# supported platforms, > the both iATU0 and iATU6 will map inbound window to BAR0. DMA will access > to the area that was previously allocated (iATU0) for BAR0, instead of the > new area (iATU6) for BAR0. > > Right now, we dodge the bullet because both iATU0 and iATU6 should > currently translate inbound accesses to BAR0 to the same allocated memory > area. However, having two separate inbound mappings for the same BAR is a > disaster waiting to happen. > > The mapping between PCI BAR and iATU inbound window are maintained in the > dw_pcie_ep::bar_to_atu[] array. While allocating a new inbound iATU map for > a BAR, dw_pcie_ep_inbound_atu() API will first check for the availability > of the existing mapping in the array and if it is not found (i.e., value in > the array indexed by the BAR is found to be 0), then it will allocate a new > map value using find_first_zero_bit(). > > The issue here is, the existing logic failed to consider the fact that the > map value '0' is a valid value for BAR0. Because, find_first_zero_bit() > will return '0' as the map value for BAR0 (note that it returns the first > zero bit position). > > Due to this, when PERST# assert + deassert happens on the PERST# supported > platforms, the inbound window allocation restarts from BAR0 and the > existing logic to find the BAR mapping will return '6' for BAR0 instead of > '0' due to the fact that it considers '0' as an invalid map value. > > So fix this issue by always incrementing the map value before assigning to > bar_to_atu[] array and then decrementing it while fetching. This will make > sure that the map value '0' always represents the invalid mapping." > > Reported-by: Niklas Cassel <Niklas.Cassel@xxxxxxx> > Closes: https://lore.kernel.org/linux-pci/ZXsRp+Lzg3x%2Fnhk3@x1-carbon/ > Tested-by: Niklas Cassel <niklas.cassel@xxxxxxx> > Fixes: 4284c88fff0e ("PCI: designware-ep: Allow pci_epc_set_bar() update inbound map address") > Reviewed-by: Niklas Cassel <niklas.cassel@xxxxxxx> > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> > Signed-off-by: Frank Li <Frank.Li@xxxxxxx> > --- Anyone take care this patch? Krzysztof Wilczyński, Lorenzo? Frank > > Notes: > Change from v3 to v4 > - commit message add "Right now, we dodge..." > - Add Reviewed-by: Manivannan Sadhasivam > > Change from v2 to v3 > - Add impact in commit message > - Add mani's detail description > - Fix Closes link > > Change from v1 to v2 > - update subject > - use free_win + 1 solution > - still leave MAX_IATU_IN as 256. I am not sure if there are platfrom have > 256 ATU. Suppose it only use max 6 in current EP framework. > - @Niklas, can you help test it. My platform become unstable today. > > drivers/pci/controller/dwc/pcie-designware-ep.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c > index 5befed2dc02b7..ba932bafdb230 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c > @@ -139,7 +139,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type, > if (!ep->bar_to_atu[bar]) > free_win = find_first_zero_bit(ep->ib_window_map, pci->num_ib_windows); > else > - free_win = ep->bar_to_atu[bar]; > + free_win = ep->bar_to_atu[bar] - 1; > > if (free_win >= pci->num_ib_windows) { > dev_err(pci->dev, "No free inbound window\n"); > @@ -153,7 +153,11 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type, > return ret; > } > > - ep->bar_to_atu[bar] = free_win; > + /* > + * Always increment free_win before assignment, since value 0 is used to identify > + * unallocated mapping. > + */ > + ep->bar_to_atu[bar] = free_win + 1; > set_bit(free_win, ep->ib_window_map); > > return 0; > @@ -190,7 +194,10 @@ static void dw_pcie_ep_clear_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no, > struct dw_pcie_ep *ep = epc_get_drvdata(epc); > struct dw_pcie *pci = to_dw_pcie_from_ep(ep); > enum pci_barno bar = epf_bar->barno; > - u32 atu_index = ep->bar_to_atu[bar]; > + u32 atu_index = ep->bar_to_atu[bar] - 1; > + > + if (!ep->bar_to_atu[bar]) > + return; > > __dw_pcie_ep_reset_bar(pci, func_no, bar, epf_bar->flags); > > -- > 2.34.1 >
