Re: [PATCH v6 0/2] PCI: dwc: Add support for 64-bit MSI target addresses

[Robin Murphy]

On 2023-01-31 12:29, Evgenii Shatokhin wrote:
> Hi,
>
> On 26.08.2022 02:54, Will McVicker wrote:
> > Hi All,
> >
> > I've update patch 2/2 to address Robin's suggestions. This includes:
> >
> >   * Dropping the while-loop for retrying with a 64-bit mask in favor of
> >     retrying within the error if-statement.
> >   * Using an int for the DMA mask instead of a bool and ternary 
> > operation.
> >
> > Thanks again for the reviews and sorry for the extra revision today!
> > Hopefully this is the last one :) If not, I'd be fine to submit patch 1/2
> > without 2/2 to avoid resending patch 1/2 for future revisions of patch 
> > 2/2
> > (unless I don't need to do that anyway).
>
> The first patch of the series made it into the mainline kernel, but, it 
> seems, the second one ("PCI: dwc: Add support for 64-bit MSI target 
> address") did not. As of 6.2-rc6, it is still missing.
>
> Was it intentionally dropped because of some issues or, perhaps, just by 
> accident? If it was by accident, could you please queue it for inclusion 
> into mainline again?

Yes, it was dropped due to the PCI_MSI_FLAGS_64BIT usage apparently 
being incorrect, and some other open debate (which all happened on the 
v5 thread):

https://lore.kernel.org/linux-pci/YzVTmy9MWh+AjshC@lpieralisi/

The DMA mask issues have now been sorted out, so you, or Will, or anyone 
else interested should be free to rework this on top of linux-next 
(although at this point, more realistically on top of 6.3-rc1 in a few 
weeks).

Thanks,
Robin.

> Support for 64-bit MSI target addresses is needed for some of our SoCs. 
> I ran into a situation when there was no available RAM in ZONE_DMA32 
> during initialization of PCIe host. Hence, dmam_alloc_coherent() failed 
> in dw_pcie_msi_host_init() and initialization failed with -ENOMEM:
>
> [    0.374834] dw-pcie 4000000.pcie0: host bridge /soc/pcie0@4000000 
> ranges:
> [    0.375813] dw-pcie 4000000.pcie0:      MEM 
> 0x0041000000..0x004fffffff -> 0x0041000000
> [    0.376171] dw-pcie 4000000.pcie0:   IB MEM 
> 0x0400000000..0x07ffffffff -> 0x0400000000
> [    0.377914] dw-pcie 4000000.pcie0: Failed to alloc and map MSI data
> [    0.378191] dw-pcie 4000000.pcie0: Failed to initialize host
> [    0.378255] dw-pcie: probe of 4000000.pcie0 failed with error -12
>
> Mainline kernel 6.2-rc6 was used in that test.
>
> The hardware supports 64-bit target addresses, so the patch "PCI: dwc: 
> Add support for 64-bit MSI target address" should help with this 
> particular failure.
>
>
> > Thanks,
> > Will
> >
> > Will McVicker (2):
> >    PCI: dwc: Drop dependency on ZONE_DMA32
> >
> > v6:
> >   * Retrying DMA allocation with 64-bit mask within the error 
> > if-statement.
> >   * Use an int for the DMA mask instead of a bool and ternary operation.
> >
> > v5:
> >   * Updated patch 2/2 to first try with a 32-bit DMA mask. On failure,
> >     retry with a 64-bit mask if supported.
> >
> > v4:
> >   * Updated commit descriptions.
> >   * Renamed msi_64b -> msi_64bit.
> >   * Dropped msi_64bit ternary use.
> >   * Dropped export of dw_pcie_msi_capabilities.
> >
> > v3:
> >    * Switched to a managed DMA allocation.
> >    * Simplified the DMA allocation cleanup.
> >    * Dropped msi_page from struct dw_pcie_rp.
> >    * Allocating a u64 instead of a full page.
> >
> > v2:
> >    * Fixed build error caught by kernel test robot
> >    * Fixed error handling reported by Isaac Manjarres
> >   PCI: dwc: Add support for 64-bit MSI target address
> >
> >   .../pci/controller/dwc/pcie-designware-host.c | 43 +++++++++----------
> >   drivers/pci/controller/dwc/pcie-designware.c  |  8 ++++
> >   drivers/pci/controller/dwc/pcie-designware.h  |  2 +-
> >   3 files changed, 30 insertions(+), 23 deletions(-)
> >
> >
> > base-commit: 568035b01cfb107af8d2e4bd2fb9aea22cf5b868
>
> Thank you in advance.
>
> Regards,
> Evgenii