RE: [PATCHv3 25/27] PCI: mobiveil: ls_pcie_g4: add Workaround for A-011451

["Z.q. Hou" <zhiqiang.hou@nxp.com>]

Hi Subbu,

Thanks a lot for your comments!

> -----Original Message-----
> From: Subrahmanya Lingappa <l.subrahmanya@mobiveil.co.in>
> Sent: 2019年2月8日 20:53
> To: Z.q. Hou <zhiqiang.hou@nxp.com>
> Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> bhelgaas@google.com; robh+dt@kernel.org; mark.rutland@arm.com;
> shawnguo@kernel.org; Leo Li <leoyang.li@nxp.com>;
> lorenzo.pieralisi@arm.com; catalin.marinas@arm.com;
> will.deacon@arm.com; Mingkai Hu <mingkai.hu@nxp.com>; M.h. Lian
> <minghuan.lian@nxp.com>; Xiaowei Bao <xiaowei.bao@nxp.com>
> Subject: Re: [PATCHv3 25/27] PCI: mobiveil: ls_pcie_g4: add Workaround for
> A-011451
> 
> ZQ,
> 
> On Tue, Jan 29, 2019 at 1:41 PM Z.q. Hou <zhiqiang.hou@nxp.com> wrote:
> >
> > From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> >
> > When LX2 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 LX2 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 patch implemented part 1, the part 2 can be set by kernel
> > parameter 'pci=pcie_bus_perf'
> >
> > This ERRATA is only for LX2160A Rev1.0, and it will be fixed in
> > Rev2.0.
> >
> > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
> > ---
> > V3:
> >  - Integrated without change from
> >
> https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpatc
> >
> hwork.ozlabs.org%2Fpatch%2F1006796%2F&amp;data=02%7C01%7Czhiqian
> g.hou%
> >
> 40nxp.com%7C90064d58a826432072c108d68dc4079d%7C686ea1d3bc2b4c
> 6fa92cd99
> >
> c5c301635%7C0%7C0%7C636852270415444442&amp;sdata=f0PrEf9%2Ff%2
> F%2B%2Fh
> > TpacZYps7HHodXwMYPLN3MB8vaqUf4%3D&amp;reserved=0
> >
> >  .../pci/controller/mobiveil/pci-layerscape-gen4.c | 15 +++++++++++++++
> >  drivers/pci/controller/mobiveil/pcie-mobiveil.h   |  4 ++++
> >  2 files changed, 19 insertions(+)
> >
> > diff --git a/drivers/pci/controller/mobiveil/pci-layerscape-gen4.c
> > b/drivers/pci/controller/mobiveil/pci-layerscape-gen4.c
> > index d2c5dbbd5e3c..20ce146788ca 100644
> > --- a/drivers/pci/controller/mobiveil/pci-layerscape-gen4.c
> > +++ b/drivers/pci/controller/mobiveil/pci-layerscape-gen4.c
> > @@ -82,12 +82,27 @@ static bool ls_pcie_g4_is_bridge(struct ls_pcie_g4
> *pcie)
> >         return header_type == PCI_HEADER_TYPE_BRIDGE;  }
> >
> > +static void workaround_A011451(struct ls_pcie_g4 *pcie) {
> > +       struct mobiveil_pcie *mv_pci = pcie->pci;
> > +       u32 val;
> > +
> > +       /* Set ACK latency timeout */
> > +       val = csr_readl(mv_pci, GPEX_ACK_REPLAY_TO);
> > +       val &= ~(ACK_LAT_TO_VAL_MASK << ACK_LAT_TO_VAL_SHIFT);
> > +       val |= (4 << ACK_LAT_TO_VAL_SHIFT);
> > +       csr_writel(mv_pci, val, GPEX_ACK_REPLAY_TO); }
> > +
> >  static int ls_pcie_g4_host_init(struct mobiveil_pcie *pci)  {
> >         struct ls_pcie_g4 *pcie = to_ls_pcie_g4(pci);
> >
> >         pcie->rev = csr_readb(pci, PCI_REVISION_ID);
> >
> > +       if (pcie->rev == REV_1_0)
> > +               workaround_A011451(pcie);
> > +
> >         return 0;
> >  }
> >
> > diff --git a/drivers/pci/controller/mobiveil/pcie-mobiveil.h
> > b/drivers/pci/controller/mobiveil/pcie-mobiveil.h
> > index ab43de5e4b2b..f0e2e4ae09b5 100644
> > --- a/drivers/pci/controller/mobiveil/pcie-mobiveil.h
> > +++ b/drivers/pci/controller/mobiveil/pcie-mobiveil.h
> > @@ -85,6 +85,10 @@
> >  #define PAB_AXI_AMAP_PEX_WIN_H(win)    PAB_REG_ADDR(0x0bac,
> win)
> >  #define PAB_INTP_AXI_PIO_CLASS         0x474
> >
> > +#define GPEX_ACK_REPLAY_TO             0x438
> > +#define  ACK_LAT_TO_VAL_MASK           0x1fff
> > +#define  ACK_LAT_TO_VAL_SHIFT          0
> > +
> >  #define PAB_PEX_AMAP_CTRL(win)         PAB_REG_ADDR(0x4ba0,
> win)
> >  #define  AMAP_CTRL_EN_SHIFT            0
> >  #define  AMAP_CTRL_TYPE_SHIFT          1
> > --
> > 2.17.1
> >
> again, can we avoid errata number on patch title and have a brief title
> instead?

Generally we do not put the ERRATA description but only the ERRATA number into the ERRATA patch subject.

Thanks,
Zhiqiang