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[PATCH] PCI,pciehp: Not write linkctrl register if val is changed

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  [PATCH] PCI,pciehp: Not write linkctrl register if val is changed Yinghai Lu <yinghai@kernel.org> - 2017-02-23 22:40 +0100

#1587126 — [PATCH] PCI,pciehp: Not write linkctrl register if val is changed

Most system have port link enabled by default, and should not
have confusing printout.

Also move printout before actully write, so could make debug print in order.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>

---
 drivers/pci/hotplug/pciehp_hpc.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Index: linux-2.6/drivers/pci/hotplug/pciehp_hpc.c
===================================================================
--- linux-2.6.orig/drivers/pci/hotplug/pciehp_hpc.c
+++ linux-2.6/drivers/pci/hotplug/pciehp_hpc.c
@@ -336,17 +336,21 @@ int pciehp_check_link_status(struct cont
 static int __pciehp_link_set(struct controller *ctrl, bool enable)
 {
 	struct pci_dev *pdev = ctrl_dev(ctrl);
-	u16 lnk_ctrl;
+	u16 lnk_ctrl, old_lnk_ctrl;
 
 	pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &lnk_ctrl);
+	old_lnk_ctrl = lnk_ctrl;
 
 	if (enable)
 		lnk_ctrl &= ~PCI_EXP_LNKCTL_LD;
 	else
 		lnk_ctrl |= PCI_EXP_LNKCTL_LD;
 
-	pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, lnk_ctrl);
+	if (old_lnk_ctrl == lnk_ctrl)
+		return 0;
+
 	ctrl_dbg(ctrl, "%s: lnk_ctrl = %x\n", __func__, lnk_ctrl);
+	pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, lnk_ctrl);
 	return 0;
 }
 

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