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".
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?
> 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
>
