On Tue, Dec 19, 2023 at 09:20:21AM -0500, Frank Li wrote:
> On Tue, Dec 19, 2023 at 10:07:14AM +0000, Niklas Cassel wrote:
> > On Mon, Dec 18, 2023 at 11:48:43PM -0500, Frank Li wrote:
> > > dw_pcie_ep_inbound_atu()
> > > {
> > > ...
> > > 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];
> > > ...
> > > }
> > >
> > > The atu index 0 is valid case for atu number. The find_first_zero_bit()
> > > will return 6 when second time call into this function if atu is 0. Suppose
> > > it should use branch 'free_win = ep->bar_to_atu[bar]'.
> > >
> > > Change 'bar_to_atu' to s8. Initialize bar_to_atu as -1 to indicate it have
> > > not allocate atu to the bar.
> > >
> > > Reported-by: Niklas Cassel <Niklas.Cassel@xxxxxxx>
> > > Close: https://lore.kernel.org/linux-pci/ZXt2A+Fusfz3luQV@x1-carbon/T/#u
> > > Fixes: 4284c88fff0e ("PCI: designware-ep: Allow pci_epc_set_bar() update inbound map address")
> > > Signed-off-by: Frank Li <Frank.Li@xxxxxxx>
> > > ---
> > >
> > > Notes:
> > > @Niklas:
> > > I have not test your case. I should be equal to previous's fix in
> > > mail list.
> >
> > Hello Frank,
> >
> > Thank you for sending a proper fix for this!
> >
> > Personally, I slightly prefer your fix that saves the iatu index + 1, and
> > keeps 0 to mean unused. That way, you don't need the memset, and you don't
> > need to change the type to signed, but either way is fine by me, so:
>
> index + 1 don't match hardware iATU index. It will be confused because
> other parts is 0 based.
>
> So I choose "-1" as free iATU.
A s8 can hold a max value of 127.
CX_ATU_NUM_OUTBOUND_REGIONS seems to be 0-255.
Since the DWC code can be synthesized with 256 iATUs,
your code will not work on systems with 128 or more iATUs.
If we continue to use a u8, and offset the saved value by one,
we will at least be able to support 255-1 == 254 iATUs.
Kind regards,
Niklas
