Re: [PATCH 1/2] PCI: dwc: ep: Fix MSI-X configuration to write to correct physical function

[Niklas Cassel]

On Mon, Feb 02, 2026 at 08:55:52AM +0100, Niklas Cassel wrote:
> On Mon, Feb 02, 2026 at 12:57:57PM +0530, Aksh Garg wrote:
> > The MSI-X configuration code reads from the correct physical function's
> > register space using dw_pcie_ep_readw_dbi(), but writes back only to
> > PF0 using the old dw_pcie_writew_dbi() helper. This causes incorrect
> > MSI-X configuration for other PFs.
> > 
> > Fix this by using dw_pcie_ep_writew_dbi() to write to the correct PF's
> > register space, matching the read operation.
> > 
> > Fixes: 70fa02ca1446 ("PCI: dwc: Add dw_pcie_ep_{read,write}_dbi[2] helpers")
> > Signed-off-by: Aksh Garg <a-garg7@xxxxxx>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-ep.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > index 7e7844ff0f7e..771241e1a2c9 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > @@ -745,7 +745,7 @@ static int dw_pcie_ep_set_msix(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> >  	val = dw_pcie_ep_readw_dbi(ep, func_no, reg);
> >  	val &= ~PCI_MSIX_FLAGS_QSIZE;
> >  	val |= nr_irqs - 1; /* encoded as N-1 */
> > -	dw_pcie_writew_dbi(pci, reg, val);
> > +	dw_pcie_ep_writew_dbi(ep, func_no, reg, val);
> >  
> >  	reg = ep_func->msix_cap + PCI_MSIX_TABLE;
> >  	val = offset | bir;
> > -- 
> > 2.34.1
> > 
> 
> Reviewed-by: Niklas Cassel <cassel@xxxxxxxxxx>
> 
> 
> However, please also fix the only remaining place in this file which still
> uses the incorrect dw_pcie_writew_dbi() instead of dw_pcie_ep_writew_dbi()
> 
> i.e.:
> dw_pcie_ep_raise_msix_irq_doorbell().

Perhaps doorbell is special, and there is only one register for this...

But then, perhaps add a comment why this is the only place that needs
to not supply func_no.