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Date: Tue, 12 Mar 2019 09:34:17 +0000
From: "Z.q. Hou" <zhiqiang.hou@....com>
To: Bjorn Helgaas <helgaas@...nel.org>
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>,
"robh+dt@...nel.org" <robh+dt@...nel.org>,
"mark.rutland@....com" <mark.rutland@....com>,
"l.subrahmanya@...iveil.co.in" <l.subrahmanya@...iveil.co.in>,
"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: [PATCHv4 26/28] PCI: mobiveil: ls_pcie_g4: add Workaround for
A-011451
Hi Bjorn,
Thanks a lot for your comments!
> -----Original Message-----
> From: Bjorn Helgaas [mailto:helgaas@...nel.org]
> Sent: 2019年3月12日 1:35
> To: Z.q. Hou <zhiqiang.hou@....com>
> Cc: linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
> robh+dt@...nel.org; mark.rutland@....com; l.subrahmanya@...iveil.co.in;
> shawnguo@...nel.org; Leo Li <leoyang.li@....com>;
> lorenzo.pieralisi@....com; catalin.marinas@....com;
> will.deacon@....com; Mingkai Hu <mingkai.hu@....com>; M.h. Lian
> <minghuan.lian@....com>; Xiaowei Bao <xiaowei.bao@....com>
> Subject: Re: [PATCHv4 26/28] PCI: mobiveil: ls_pcie_g4: add Workaround for
> A-011451
>
> On Mon, Mar 11, 2019 at 09:33:32AM +0000, Z.q. Hou 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'
>
> If I understand correctly, you're saying that LX2160A Rev1.0 will only work
> correctly if you have this patch applied AND you boot with
> "pci=pcie_bus_perf".
>
Your understanding is correct.
> That might be OK if these rev 1.0 parts are only used in the lab and are never
> shipped to customers. But if these parts are ever shipped to customers, I
> don't think it's acceptable for them to have to figure out that they must boot
> with "pci=pcie_bus_perf". Yes, you can document that in release notes, but
> it's still a poor user experience, and users will forget, and they will see
> mysterious hard-to-debug issues.
>
> Maybe there's a way for you to automatically set that pcie_bus_perf mode?
> With a dmesg note to indicate that you're overriding any mode the user may
> have selected?
>
Actually we don't have a way to set the pcie_bus_perf automatically under Linux, we give this parameter in kernel cmdline.
Do you have any advice about how to set this parameter automatically under Linux?
> > This ERRATA is only for LX2160A Rev1.0, and it will be fixed in
> > Rev2.0.
> >
> > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> > ---
> > V4:
> > - no change
> >
> > .../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
> >
Thanks,
Zhiqiang
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