Re: [PATCH 1/1] PCI: qcom: Add early fixup to set the max payload size for IPQ9574

[Praveenkumar I]

On 7/24/2023 7:39 PM, Manivannan Sadhasivam wrote:
> On Mon, Jul 24, 2023 at 06:38:55PM +0530, Manivannan Sadhasivam wrote:
> > On Mon, Jul 24, 2023 at 02:53:37PM +0200, Konrad Dybcio wrote:
> > > On 24.07.2023 14:47, Praveenkumar I wrote:
> > > > Set 256 bytes as payload size for IPQ9574 via early fixup. This allows
> > > > PCIe RC to use the max payload size when a capable link partner is
> > > > connected.
> > > >
> > > > Signed-off-by: Praveenkumar I <quic_ipkumar@xxxxxxxxxxx>
> > > > ---
> > > [...]
> > >
> > > > +static void qcom_fixup_mps_256(struct pci_dev *dev)
> > > > +{
> > > > +	pcie_set_mps(dev, 256);
> > > Looks like setting "dev->pcie_mpss = 1" here would make the PCIe generic
> > > code take care of this.
> > Right, also this setting should not be PCI-PCI bridge specific but rather
> > controller specific.
> Wait, have you tested this patch with PCIe devices having MPS < 256 i.e.,
> default 128?
>
> Take a look at this discussion: https://lore.kernel.org/all/20230608093652.1409485-1-vidyas@xxxxxxxxxx/
>
> - Mani
Yes, tested this patch with PCIe devices having default 128 and RC is 
falling back to 128 when pci device is added.
This is handled inside pci_configure_mps().
/        mpss = 128 << dev->pcie_mpss;/
/        if (mpss < p_mps && pci_pcie_type(bridge) == 
PCI_EXP_TYPE_ROOT_PORT) {/
/                pcie_set_mps(bridge, mpss);/
/                pci_info(dev, "Upstream bridge's Max Payload Size set 
to %d (was %d, max %d)\n",/
/                         mpss, p_mps, 128 << bridge->pcie_mpss);/
/                p_mps = pcie_get_mps(bridge);/
/        }/
//
Also getting the below print,
/[    2.011963] pci 0003:01:00.0: Upstream bridge's Max Payload Size set 
to 128 (was 256, max 256)/
> > - Mani
> >
> > > Konrad
> > --
> > மணிவண்ணன் சதாசிவம்
--
Thanks,
Praveenkumar