linux-kernel - Re: [PATCH] PCI: dwc: meson add quirk

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Date:   Sat, 19 Jun 2021 11:01:53 +0800
From:   Art Nikpal <email2tema@...il.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     Rob Herring <robh@...nel.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Yue Wang <yue.wang@...ogic.com>,
        Kevin Hilman <khilman@...libre.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczynski <kw@...ux.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Christian Hewitt <christianshewitt@...il.com>,
        PCI <linux-pci@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Artem Lapkin <art@...das.com>, Nick Xie <nick@...das.com>,
        Gouwa Wang <gouwa@...das.com>
Subject: Re: [PATCH] PCI: dwc: meson add quirk

> Neil
> It should be enabled only when the Amlogic bridge is present, thus similar filtering as keystone & loongon
> is needed, but with such filtering we could reuse ks_pcie_quirk() and loongson_mrrs_quirk() as is.
> AFAIL Simply moving ks_pcie_quirk() and loongson_mrrs_quirk() to core with the amlogic pci IDS added would be sufficient here.

My patch was not a good solution! its was just example how to fix our
problem - need to remade it

Yes i'm agree with Neil , at this moment we can move (replace
duplicate functionalities)  ks_pcie_quirk() and loongson_mrrs_quirk()
to core  + add amlogic pci IDS PCI_DEVICE(PCI_VENDOR_ID_SYNOPSYS,
PCI_DEVICE_ID_SYNOPSYS_HAPSUSB3) - without other changes for everyone,
and after we can improve this quirk by next patches

i will send new patches variant soon

On Fri, Jun 18, 2021 at 11:08 PM Neil Armstrong <narmstrong@...libre.com> wrote:
>
> On 18/06/2021 16:30, Rob Herring wrote:
> > On Fri, Jun 18, 2021 at 6:12 AM Martin Blumenstingl
> > <martin.blumenstingl@...glemail.com> wrote:
> >>
> >> Hi Artem,
> >>
> >> On Fri, Jun 18, 2021 at 8:38 AM Artem Lapkin <email2tema@...il.com> wrote:
> >>>
> >>> Device set same 256 bytes maximum read request size equal MAX_READ_REQ_SIZE
> >>> was find some issue with HDMI scrambled picture and nvme devices
> >>> at intensive writing...
> >>>
> >>> [    4.798971] nvme 0000:01:00.0: fix MRRS from 512 to 256
> >>>
> >>> This quirk setup same MRRS if we try solve this problem with
> >>> pci=pcie_bus_perf kernel command line param
> >> thank you for investigating this issue and for providing a fix!
> >>
> >> [...]
> >>> +static void meson_pcie_quirk(struct pci_dev *dev)
> >>> +{
> >>> +       int mrrs;
> >>> +
> >>> +       /* no need quirk */
> >>> +       if (pcie_bus_config != PCIE_BUS_DEFAULT)
> >>> +               return;
> >>> +
> >>> +       /* no need for root bus */
> >>> +       if (pci_is_root_bus(dev->bus))
> >>> +               return;
> >>> +
> >>> +       mrrs = pcie_get_readrq(dev);
> >>> +
> >>> +       /*
> >>> +        * set same 256 bytes maximum read request size equal MAX_READ_REQ_SIZE
> >>> +        * was find some issue with HDMI scrambled picture and nvme devices
> >>> +        * at intensive writing...
> >>> +        */
> >>> +
> >>> +       if (mrrs != MAX_READ_REQ_SIZE) {
> >>> +               dev_info(&dev->dev, "fix MRRS from %d to %d\n", mrrs, MAX_READ_REQ_SIZE);
> >>> +               pcie_set_readrq(dev, MAX_READ_REQ_SIZE);
> >>> +       }
> >>> +}
> >>> +DECLARE_PCI_FIXUP_ENABLE(PCI_ANY_ID, PCI_ANY_ID, meson_pcie_quirk);
> >
> > Isn't this going to run for everyone if meson driver happens to be enabled?
>
> It should be enabled only when the Amlogic bridge is present, thus similar filtering as keystone & loongon
> is needed, but with such filtering we could reuse ks_pcie_quirk() and loongson_mrrs_quirk() as is.
>
> >
> >> it seems that other PCIe controllers need something similar. in
> >> particular I found pci-keystone [0] and pci-loongson [1]
> >> while comparing your code with the two existing implementations two
> >> things came to my mind:
> >> 1. your implementation slightly differs from the two existing ones as
> >> it's not walking through the parent PCI busses (I think this would be
> >> relevant if there's another bridge between the host bridge and the
> >> actual device)
> >> 2. (this is a question towards the PCI maintainers) does it make sense
> >> to have this MRRS quirk re-usable somewhere?
> >
> > Yes. Ideally, the max size could just be data in the bus or bridge
> > struct and perhaps some flags too, then the core can handle
> > everything.
>
> AFAIL Simply moving ks_pcie_quirk() and loongson_mrrs_quirk() to core with the amlogic pci IDS added would be sufficient here.
>
> Neil
>
> >
> > Rob
> >
>