Hi Bjorn, Thanks a lot for your comments! > -----Original Message----- > From: Bjorn Helgaas [mailto:helgaas@xxxxxxxxxx] > Sent: 2019年3月12日 1:35 > To: Z.q. Hou <zhiqiang.hou@xxxxxxx> > Cc: linux-pci@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; l.subrahmanya@xxxxxxxxxxxxxx; > shawnguo@xxxxxxxxxx; Leo Li <leoyang.li@xxxxxxx>; > lorenzo.pieralisi@xxxxxxx; catalin.marinas@xxxxxxx; > will.deacon@xxxxxxx; Mingkai Hu <mingkai.hu@xxxxxxx>; M.h. Lian > <minghuan.lian@xxxxxxx>; Xiaowei Bao <xiaowei.bao@xxxxxxx> > 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@xxxxxxx> > > > > 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@xxxxxxx> > > --- > > 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
