Re: [PATCH v2 07/10] PCI: layerscape: Modify the MSIX to the doorbell way

[Andrew Murray]

On Sat, Aug 24, 2019 at 12:08:40AM +0000, Xiaowei Bao wrote:
> 
> 
> > -----Original Message-----
> > From: Andrew Murray <andrew.murray@xxxxxxx>
> > Sent: 2019å8æ23æ 21:58
> > To: Xiaowei Bao <xiaowei.bao@xxxxxxx>
> > Cc: bhelgaas@xxxxxxxxxx; robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx;
> > shawnguo@xxxxxxxxxx; Leo Li <leoyang.li@xxxxxxx>; kishon@xxxxxx;
> > lorenzo.pieralisi@xxxxxx; arnd@xxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx; M.h.
> > Lian <minghuan.lian@xxxxxxx>; Mingkai Hu <mingkai.hu@xxxxxxx>; Roy
> > Zang <roy.zang@xxxxxxx>; jingoohan1@xxxxxxxxx;
> > gustavo.pimentel@xxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx
> > Subject: Re: [PATCH v2 07/10] PCI: layerscape: Modify the MSIX to the
> > doorbell way
> > 
> > On Thu, Aug 22, 2019 at 07:22:39PM +0800, Xiaowei Bao wrote:
> > > The layerscape platform use the doorbell way to trigger MSIX interrupt
> > > in EP mode.
> > >
> > 
> > I have no problems with this patch, however...
> > 
> > Are you able to add to this message a reason for why you are making this
> > change? Did dw_pcie_ep_raise_msix_irq not work when func_no != 0? Or did
> > it work yet dw_pcie_ep_raise_msix_irq_doorbell is more efficient?
> 
> The fact is that, this driver is verified in ls1046a platform of NXP before, and ls1046a don't
> support MSIX feature, so I set the msix_capable of pci_epc_features struct is false,
> but in other platform, e.g. ls1088a, it support the MSIX feature, I verified the MSIX
> feature in ls1088a, it is not OK, so I changed to another way. Thanks.

Right, so the existing pci-layerscape-ep.c driver never supported MSIX yet it
erroneously had a switch case statement to call dw_pcie_ep_raise_msix_irq which
would never get used.

Now that we're adding a platform with MSIX support the existing
dw_pcie_ep_raise_msix_irq doesn't work (for this platform) so we are adding a
different method.

Given that dw_pcie_ep_raise_msix_irq is used by pcie-designware-plat.c we
can assume this function at least works for it's use case.

Please update the commit message - It would be helpful to suggest that
dw_pcie_ep_raise_msix_irq was never called in the exisitng driver because
msix_capable was always set to false.

Thanks,

Andrew Murray

> 
> > 
> > Thanks,
> > 
> > Andrew Murray
> > 
> > > Signed-off-by: Xiaowei Bao <xiaowei.bao@xxxxxxx>
> > > ---
> > > v2:
> > >  - No change.
> > >
> > >  drivers/pci/controller/dwc/pci-layerscape-ep.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-layerscape-ep.c
> > > b/drivers/pci/controller/dwc/pci-layerscape-ep.c
> > > index 8461f62..7ca5fe8 100644
> > > --- a/drivers/pci/controller/dwc/pci-layerscape-ep.c
> > > +++ b/drivers/pci/controller/dwc/pci-layerscape-ep.c
> > > @@ -74,7 +74,8 @@ static int ls_pcie_ep_raise_irq(struct dw_pcie_ep *ep,
> > u8 func_no,
> > >  	case PCI_EPC_IRQ_MSI:
> > >  		return dw_pcie_ep_raise_msi_irq(ep, func_no, interrupt_num);
> > >  	case PCI_EPC_IRQ_MSIX:
> > > -		return dw_pcie_ep_raise_msix_irq(ep, func_no, interrupt_num);
> > > +		return dw_pcie_ep_raise_msix_irq_doorbell(ep, func_no,
> > > +							  interrupt_num);
> > >  	default:
> > >  		dev_err(pci->dev, "UNKNOWN IRQ type\n");
> > >  		return -EINVAL;
> > > --
> > > 2.9.5
> > >