linux-kernel - Re: [PATCHv3 25/27] PCI: mobiveil: ls_pcie

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Date:   Fri, 8 Feb 2019 18:23:18 +0530
From:   Subrahmanya Lingappa <l.subrahmanya@...iveil.co.in>
To:     "Z.q. Hou" <zhiqiang.hou@....com>
Cc:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        Mingkai Hu <mingkai.hu@....com>,
        "M.h. Lian" <minghuan.lian@....com>,
        Xiaowei Bao <xiaowei.bao@....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@....com> wrote:
>
> From: Hou Zhiqiang <Zhiqiang.Hou@....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@....com>
> ---
> V3:
>  - Integrated without change from http://patchwork.ozlabs.org/patch/1006796/
>
>  .../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?