Re: [PATCH] NTB: Fix an error in get link status

From: Jiasen Lin
Date: Mon Nov 18 2019 - 05:24:05 EST

On 2019/11/18 7:00, Jon Mason wrote:
On Thu, Nov 7, 2019 at 4:37 AM Jiasen Lin <linjiasen@xxxxxxxx> wrote:

The offset of PCIe Capability Header for AMD and HYGON NTB is 0x64,
but the macro which named "AMD_LINK_STATUS_OFFSET" is defined as 0x68.
It is offset of Device Capabilities Reg rather than Link Control Reg.

This code trigger an error in get link statsus:

cat /sys/kernel/debug/ntb_hw_amd/0000:43:00.1/info
LNK STA - 0x8fa1
Link Status - Up
Link Speed - PCI-E Gen 0
Link Width - x0

This patch use pcie_capability_read_dword to get link status.
After fix this issue, we can get link status accurately:

cat /sys/kernel/debug/ntb_hw_amd/0000:43:00.1/info
LNK STA - 0x11030042
Link Status - Up
Link Speed - PCI-E Gen 3
Link Width - x16

No response from AMD maintainers, but it looks like you are correct.

This needs a "Fixes:" line here. I took the liberty of adding one to
this patch.

Thank you for your suggestions. Yes, this patch fix the commit id: a1b3695 ("NTB: Add support for AMD PCI-Express Non-Transparent Bridge").

Signed-off-by: Jiasen Lin <linjiasen@xxxxxxxx>
drivers/ntb/hw/amd/ntb_hw_amd.c | 5 +++--
drivers/ntb/hw/amd/ntb_hw_amd.h | 1 -
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/ntb/hw/amd/ntb_hw_amd.c b/drivers/ntb/hw/amd/ntb_hw_amd.c
index 156c2a1..ae91105 100644
--- a/drivers/ntb/hw/amd/ntb_hw_amd.c
+++ b/drivers/ntb/hw/amd/ntb_hw_amd.c
@@ -855,8 +855,8 @@ static int amd_poll_link(struct amd_ntb_dev *ndev)

ndev->cntl_sta = reg;

- rc = pci_read_config_dword(ndev->ntb.pdev,
+ rc = pcie_capability_read_dword(ndev->ntb.pdev,
+ PCI_EXP_LNKCTL, &stat);
if (rc)
return 0;
ndev->lnk_sta = stat;
@@ -1139,6 +1139,7 @@ static const struct ntb_dev_data dev_data[] = {
static const struct pci_device_id amd_ntb_pci_tbl[] = {
{ PCI_VDEVICE(AMD, 0x145b), (kernel_ulong_t)&dev_data[0] },
{ PCI_VDEVICE(AMD, 0x148b), (kernel_ulong_t)&dev_data[1] },
+ { PCI_VDEVICE(HYGON, 0x145b), (kernel_ulong_t)&dev_data[0] },

This should be a separate patch. I took the liberty of splitting it
off into a unique patch and attributing it to you. I've pushed them
to the ntb-next branch on

Thank you for your comment. We appreciate the time and effort you have spent to split it off, I will test it ASAP.

Please verify everything looks acceptable to you (given the changes I
did above that are attributed to you). Also, testing of the latest
code is always appreciated.


{ 0, }
MODULE_DEVICE_TABLE(pci, amd_ntb_pci_tbl);
diff --git a/drivers/ntb/hw/amd/ntb_hw_amd.h b/drivers/ntb/hw/amd/ntb_hw_amd.h
index 139a307..39e5d18 100644
--- a/drivers/ntb/hw/amd/ntb_hw_amd.h
+++ b/drivers/ntb/hw/amd/ntb_hw_amd.h
@@ -53,7 +53,6 @@
#include <linux/pci.h>

#define AMD_LINK_HB_TIMEOUT msecs_to_jiffies(1000)
#define NTB_LIN_STA_ACTIVE_BIT 0x00000002
#define NTB_LNK_STA_SPEED_MASK 0x000F0000
#define NTB_LNK_STA_WIDTH_MASK 0x03F00000

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Jiasen Lin