The Target Speed quirk in pcie_failed_link_retrain() uses the presence
of LBMS bit as one of the triggering conditions effectively
monopolizing the use of that bit. An upcoming change will introduce a
PCIe bandwidth controller which sets up an interrupt to track LBMS. As
LBMS will be cleared by the interrupt handler, the Target Speed quirk
will no longer be able to observe LBMS directly.

As a preparatory step for the change, extract the LBMS seen check into
own function out of pcie_failed_link_retrain().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/quirks.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index dccb60c1d9cc..a560ea403b8e 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -33,6 +33,11 @@
 #include <linux/switchtec.h>
 #include "pci.h"
 
+static bool pcie_lbms_seen(struct pci_dev *dev, u16 lnksta)
+{
+	return lnksta & PCI_EXP_LNKSTA_LBMS;
+}
+
 /*
  * Retrain the link of a downstream PCIe port by hand if necessary.
  *
@@ -96,8 +101,7 @@ int pcie_failed_link_retrain(struct pci_dev *dev)
 
 	pcie_capability_read_word(dev, PCI_EXP_LNKCTL2, &lnkctl2);
 	pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
-	if ((lnksta & (PCI_EXP_LNKSTA_LBMS | PCI_EXP_LNKSTA_DLLLA)) ==
-	    PCI_EXP_LNKSTA_LBMS) {
+	if (!(lnksta & PCI_EXP_LNKSTA_DLLLA) && pcie_lbms_seen(dev, lnksta)) {
 		u16 oldlnkctl2 = lnkctl2;
 
 		pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
-- 
2.39.5

On Wed,  9 Oct 2024 12:52:19 +0300
Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> wrote:

> The Target Speed quirk in pcie_failed_link_retrain() uses the presence
> of LBMS bit as one of the triggering conditions effectively
> monopolizing the use of that bit. An upcoming change will introduce a
> PCIe bandwidth controller which sets up an interrupt to track LBMS. As
> LBMS will be cleared by the interrupt handler, the Target Speed quirk
> will no longer be able to observe LBMS directly.
> 
> As a preparatory step for the change, extract the LBMS seen check into
> own function out of pcie_failed_link_retrain().
extract the LBMS seen check from pcie_failed_link_retrain() into
a new function pcie_lmbs_seen()

perhaps is slightly clearer?
> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>