On Thu, Aug 08, 2019 at 07:01:03AM +0000, Koenig, Christian wrote: > Am 08.08.19 um 01:01 schrieb Bjorn Helgaas: > > On Fri, Jul 26, 2019 at 12:55:52AM +0530, Sumit Saxena wrote: > >> In Resize BAR control register, bits[8:12] represents size of BAR. > >> As per PCIe specification, below is encoded values in register bits > >> to actual BAR size table: > >> > >> Bits BAR size > >> 0 1 MB > >> 1 2 MB > >> 2 4 MB > >> 3 8 MB > >> -- > >> > >> For 1 MB BAR size, BAR size bits should be set to 0 but incorrectly > >> these bits are set to "1f". Latest megaraid_sas and mpt3sas adapters > >> which support Resizable BAR with 1 MB BAR size fails to initialize > >> during system resume from S3 sleep. > >> > >> Fix: Correctly calculate BAR size bits for Resize BAR control register. > >> > >> V2: > >> -Simplified calculation of BAR size bits as suggested by Christian Koenig. > >> > >> CC: stable@xxxxxxxxxxxxxxx # v4.16+ > >> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203939 > >> Fixes: d3252ace0bc652a1a244455556b6a549f969bf99 ("PCI: Restore resized BAR state on resume") > >> Signed-off-by: Sumit Saxena <sumit.saxena@xxxxxxxxxxxx> > >> --- > >> drivers/pci/pci.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > >> index 29ed5ec1ac27..e59921296125 100644 > >> --- a/drivers/pci/pci.c > >> +++ b/drivers/pci/pci.c > >> @@ -1438,7 +1438,7 @@ static void pci_restore_rebar_state(struct pci_dev *pdev) > >> pci_read_config_dword(pdev, pos + PCI_REBAR_CTRL, &ctrl); > >> bar_idx = ctrl & PCI_REBAR_CTRL_BAR_IDX; > >> res = pdev->resource + bar_idx; > >> - size = order_base_2((resource_size(res) >> 20) | 1) - 1; > >> + size = order_base_2(resource_size(res) >> 20); > > Since BAR sizes are always powers of 2, wouldn't this be simpler as: > > > > size = ilog2(resource_size(res)) - 20; > > > > which nicely matches the table in PCIe r5.0, sec 7.8.6.3? > > Yeah, that should obviously work as well. > > We would have a serious problem in the resource management if the > resource size is smaller than 1MB or not a power of two. Yes, definitely. Resizable BARs are required by spec to be 1MB or larger, but this does niggle at me a little bit, too. It probably saves a few bits in pci_dev to recompute this at restore-time, but honestly, I think it would be more obviously correct to just do the simple-minded thing of saving and restoring the entire register. > Feel free to add my r-b. Done, thanks! > Regards, > Christian. > > > > >> ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE; > >> ctrl |= size << PCI_REBAR_CTRL_BAR_SHIFT; > >> pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl); > >> -- > >> 2.18.1 > >> >
