On Tue, Dec 19, 2023 at 02:38:34PM +0000, Niklas Cassel wrote:
> 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.
>
Agree. I cannot suggest a better alternative. So let's go with this. But please
add a comment before bar_to_atu assignment to make it clear. Like,
/*
* Always increment free_win before assignment, since value 0 is used to
* identify unallocated mapping.
*/
ep->bar_to_atu[bar] = free_win + 1;
- Mani
>
> Kind regards,
> Niklas
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