[PATCH v3 02/10] PCI: Make link retraining use RMW accessors for changing LNKCTL

Ilpo Järvinen
2023-06-20T13:47:11Z

Don't assume that the device is fully under the control of PCI core.
Use RMW capability accessors in link retraining which do proper locking
to avoid losing concurrent updates to the register values.

Fixes: 4ec73791a64b ("PCI: Work around Pericom PCIe-to-PCI bridge Retrain Link erratum")
Fixes: 7d715a6c1ae5 ("PCI: add PCI Express ASPM support")
Suggested-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Cc: stable@vger.kernel.org
---

pci/enumeration branch moves the link retraining code into PCI core and
also conflicts with a link retraining fix in pci/aspm. The changelog
(and patch splitting) takes the move into account by not referring to
ASPM while the change itself is not based on pci/enumeration (as per
Bjorn's preference).

---
drivers/pci/pcie/aspm.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 66d7514ca111..50e32bda4656 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -199,17 +199,14 @@ static bool pcie_retrain_link(struct pcie_link_state *link)
unsigned long end_jiffies;
u16 reg16;

- pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &reg16);
- reg16 |= PCI_EXP_LNKCTL_RL;
- pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
+ pcie_capability_set_word(parent, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_RL);
if (parent->clear_retrain_link) {
/*
* Due to an erratum in some devices the Retrain Link bit
* needs to be cleared again manually to allow the link
* training to succeed.
*/
- reg16 &= ~PCI_EXP_LNKCTL_RL;
- pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
+ pcie_capability_clear_word(parent, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_RL);
}

/* Wait for link training end. Break out after waiting for timeout */
--
2.30.2