[U-Boot] [PATCHv3 10/11] pci: ls_pcie_g4: Add Workaround for A-011451

Z.q. Hou zhiqiang.hou at nxp.com
Mon Feb 18 01:34:09 UTC 2019


Hi Bin,

Thanks a lot for your comments!

> -----Original Message-----
> From: Bin Meng <bmeng.cn at gmail.com>
> Sent: 2019年2月14日 14:17
> To: Z.q. Hou <zhiqiang.hou at nxp.com>
> Cc: u-boot at lists.denx.de; albert.u.boot at aribaud.net; Priyanka Jain
> <priyanka.jain at nxp.com>; York Sun <york.sun at nxp.com>;
> sriram.dash at nxp.com; yamada.masahiro at socionext.com; Prabhakar
> Kushwaha <prabhakar.kushwaha at nxp.com>; Mingkai Hu
> <mingkai.hu at nxp.com>; M.h. Lian <minghuan.lian at nxp.com>
> Subject: Re: [U-Boot] [PATCHv3 10/11] pci: ls_pcie_g4: Add Workaround for
> A-011451
> 
> Hi Zhiqiang,
> 
> On Thu, Feb 14, 2019 at 11:52 AM Z.q. Hou <zhiqiang.hou at nxp.com> wrote:
> >
> > Hi Bin,
> >
> > Thanks a lot for your comments!
> >
> > > -----Original Message-----
> > > From: Bin Meng <bmeng.cn at gmail.com>
> > > Sent: 2019年2月12日 11:45
> > > To: Z.q. Hou <zhiqiang.hou at nxp.com>
> > > Cc: u-boot at lists.denx.de; albert.u.boot at aribaud.net; Priyanka Jain
> > > <priyanka.jain at nxp.com>; York Sun <york.sun at nxp.com>;
> > > sriram.dash at nxp.com; yamada.masahiro at socionext.com; Prabhakar
> > > Kushwaha <prabhakar.kushwaha at nxp.com>; Mingkai Hu
> > > <mingkai.hu at nxp.com>; M.h. Lian <minghuan.lian at nxp.com>
> > > Subject: Re: [U-Boot] [PATCHv3 10/11] pci: ls_pcie_g4: Add
> > > Workaround for
> > > A-011451
> > >
> > > Hi,
> > >
> > > On Fri, Jan 25, 2019 at 6:07 PM Z.q. Hou <zhiqiang.hou at nxp.com> wrote:
> > > >
> > > > From: Hou Zhiqiang <Zhiqiang.Hou at nxp.com>
> > > >
> > > > When LAYERSCAPE Gen4 PCIe controller is sending multiple split
> > > > completions and ACK latency expires indicating that ACK should be
> > > > send at priority. But because of large number of split completions
> > > > and FC update DLLP, the controller does not give priority to ACK
> > > > transmission. This results into ACK latency timer timeout error at
> > > > the link partner and the pending TLPs are replayed by the link
> > > > partner again.
> > > >
> > > > Workaround:
> > > > 1. Reduce the ACK latency timeout value to a very small value.
> > > > 2. Restrict the number of completions from the PCIe controller
> > > >    to 1, by changing the Max Read Request Size (MRRS) of link
> > > >    partner to the same value as Max Packet size (MPS).
> > > >
> > > > This ERRATA is only for LX2160A Rev1.0 and will be fixed in Rev2.0.
> > > >
> > > > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou at nxp.com>
> > > > ---
> > > > V3:
> > > >  - New patch.
> > > >
> > > >  drivers/pci/pci_auto.c             | 34
> > > ++++++++++++++++++++++++++++++
> > > >  drivers/pci/pcie_layerscape_gen4.c |  8 +++++++
> > > > drivers/pci/pcie_layerscape_gen4.h |  4 ++++
> > > >  include/pci.h                      |  9 ++++++++
> > > >  include/pci_ids.h                  |  1 +
> > > >  5 files changed, 56 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/pci_auto.c b/drivers/pci/pci_auto.c index
> > > > d7237f6eee..37307bd54b 100644
> > > > --- a/drivers/pci/pci_auto.c
> > > > +++ b/drivers/pci/pci_auto.c
> > > > @@ -22,6 +22,7 @@ void dm_pciauto_setup_device(struct udevice
> > > > *dev,
> > > int bars_num,
> > > >                              struct pci_region *prefetch, struct
> > > pci_region *io,
> > > >                              bool enum_only)  {
> > > > +       struct udevice *rp = pci_get_controller(dev);
> > > >         u32 bar_response;
> > > >         pci_size_t bar_size;
> > > >         u16 cmdstat = 0;
> > > > @@ -32,6 +33,9 @@ void dm_pciauto_setup_device(struct udevice
> > > > *dev,
> > > int bars_num,
> > > >         struct pci_region *bar_res = NULL;
> > > >         int found_mem64 = 0;
> > > >         u16 class;
> > > > +       int pos;
> > > > +       u16 val, vendor, dev_id;
> > > > +       u8 rev;
> > > >
> > > >         dm_pci_read_config16(dev, PCI_COMMAND, &cmdstat);
> > > >         cmdstat = (cmdstat & ~(PCI_COMMAND_IO |
> > > PCI_COMMAND_MEMORY)) |
> > > > @@ -161,6 +165,36 @@ void dm_pciauto_setup_device(struct udevice
> > > *dev, int bars_num,
> > > >         dm_pci_write_config8(dev, PCI_CACHE_LINE_SIZE,
> > > >
> CONFIG_SYS_PCI_CACHE_LINE_SIZE);
> > > >         dm_pci_write_config8(dev, PCI_LATENCY_TIMER, 0x80);
> > > > +
> > > > +       /*
> > > > +        * When NXP LAYERSCAPE Gen4 PCIe controller is sending
> > > multiple split
> > > > +        * completions and ACK latency expires indicating that ACK
> > > > + should
> > > be
> > > > +        * send at priority. But because of large number of split
> > > completions
> > > > +        * and FC update DLLP, the controller does not give priority to
> ACK
> > > > +        * transmission. This results into ACK latency timer
> > > > + timeout error
> > > at
> > > > +        * the link partner and the pending TLPs are replayed by the
> link
> > > > +        * partner again.
> > > > +        *
> > > > +        * The workaround:
> > > > +        * Restrict the number of completions from the PCIe
> > > > + controller to
> > > 1,
> > > > +        * by changing the Max Read Request Size (MRRS) of link
> > > > + partner
> > > to the
> > > > +        * same value as Max Packet size (MPS).
> > > > +        *
> > > > +        * So, set both the MPS and MRRS to the minimum 128B.
> > > > +        */
> > > > +       dm_pci_read_config16(rp, PCI_VENDOR_ID, &vendor);
> > > > +       dm_pci_read_config16(rp, PCI_DEVICE_ID, &dev_id);
> > > > +       dm_pci_read_config8(rp, PCI_REVISION_ID, &rev);
> > > > +       if (vendor == PCI_VENDOR_ID_FREESCALE &&
> > > > +           dev_id == PCI_DEVICE_ID_LX2160A && rev == 0x10) {
> > > > +               pos = dm_pci_find_capability(dev,
> PCI_CAP_ID_EXP);
> > > > +               if (pos) {
> > > > +                       dm_pci_read_config16(dev, pos +
> > > PCI_EXP_DEVCTL, &val);
> > > > +                       val &= ~(PCI_EXP_DEVCTL_READRQ |
> > > > +                                PCI_EXP_DEVCTL_PAYLOAD);
> > > > +                       dm_pci_write_config16(dev, pos +
> > > PCI_EXP_DEVCTL, val);
> > > > +               }
> > > > +       }
> > >
> > > Can this be done in the probe() routine of the driver codes?
> >
> > No, not only the RC itself but also all the EP devices need to setup the same
> MPS and MRRS, it is hard to scan the PCIe EP devices in the RC driver (a
> platform driver).
> >
> 
> If this is the case, I think we need split the patch into 2 commits:
> 
> - 1 commit to update the PCI library to program MPS and MRRS. This can be
> generic though.
> - 1 commit to update the gen4 PCIe driver for the workaround

Thanks for your suggestion! Will split it.
 
> 
> BTW: the default MPS and MRRS should be 128B per the PCIe spec. I am
> wondering why the gen4 PCIe RC does not follow the spec.

The default MPS is 128B but default MRRS is 512B in the spec. And this is a NXP Gen4 PCIe controller's ERRATA as descripted in the comments that result in the NXP RC does not work well with the default value.

> 
> Regards,
> Bin

Thanks,
Zhiqiang


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