On Tue, Mar 12, 2019 at 09:34:17AM +0000, Z.q. Hou wrote:

Hi Bjorn,

Thanks a lot for your comments!

quoted

-----Original Message-----
From: Bjorn Helgaas [mailto:helgaas@kernel.org]
Sent: 2019年3月12日 1:35
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;
robh+dt@kernel.org; mark.rutland@arm.com; l.subrahmanya@mobiveil.co.in;
shawnguo@kernel.org; Leo Li [off-list ref];
lorenzo.pieralisi@arm.com; catalin.marinas@arm.com;
will.deacon@arm.com; Mingkai Hu [off-list ref]; M.h. Lian
[off-list ref]; Xiaowei Bao [off-list ref]
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:

quoted

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'

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.

quoted

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.

Since you didn't respond here, I assume these rev 1.0 parts have been
or will be shipped to end users?  Please confirm.

quoted

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?

The beauty of Linux being open-source is that if you need something
that doesn't exist, you are empowered to create it.

We do have one place already (cns3xxx_pcie_hw_init()) that explicitly
sets pcie_bus_config.  You might be able to do something similar.

quoted

quoted

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>
---
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)

quoted

 	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)

quoted

 #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)

quoted

 #define  AMAP_CTRL_EN_SHIFT		0
 #define  AMAP_CTRL_TYPE_SHIFT		1
--
2.17.1

Thanks,
Zhiqiang

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