return pci_dev_wait(dev, "PM D3hot->D0", PCIE_RESET_READY_POLL_MS);
}
- * Return TRUE if successful, or FALSE if status has not changed within
+ /**
+ * pcie_wait_for_link_status - Wait for link status change
+ * @pdev: Device whose link to wait for.
+ * @use_lt: Use the LT bit if TRUE, or the DLLLA bit if FALSE.
+ * @active: Waiting for active or inactive?
+ *
-static bool pcie_wait_for_link_status(struct pci_dev *pdev,
- bool use_lt, bool active)
++ * Return 0 if successful, or -ETIMEDOUT if status has not changed within
+ * PCIE_LINK_RETRAIN_TIMEOUT_MS milliseconds.
+ */
- break;
++static int pcie_wait_for_link_status(struct pci_dev *pdev,
++ bool use_lt, bool active)
+ {
+ u16 lnksta_mask, lnksta_match;
+ unsigned long end_jiffies;
+ u16 lnksta;
+
+ lnksta_mask = use_lt ? PCI_EXP_LNKSTA_LT : PCI_EXP_LNKSTA_DLLLA;
+ lnksta_match = active ? lnksta_mask : 0;
+
+ end_jiffies = jiffies + msecs_to_jiffies(PCIE_LINK_RETRAIN_TIMEOUT_MS);
+ do {
+ pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta);
+ if ((lnksta & lnksta_mask) == lnksta_match)
- return (lnksta & lnksta_mask) == lnksta_match;
++ return 0;
+ msleep(1);
+ } while (time_before(jiffies, end_jiffies));
- * Return TRUE if successful, or FALSE if training has not completed
++
++ return -ETIMEDOUT;
+ }
+
+ /**
+ * pcie_retrain_link - Request a link retrain and wait for it to complete
+ * @pdev: Device whose link to retrain.
+ * @use_lt: Use the LT bit if TRUE, or the DLLLA bit if FALSE, for status.
+ *
+ * Retrain completion status is retrieved from the Link Status Register
+ * according to @use_lt. It is not verified whether the use of the DLLLA
+ * bit is valid.
+ *
-bool pcie_retrain_link(struct pci_dev *pdev, bool use_lt)
++ * Return 0 if successful, or -ETIMEDOUT if training has not completed
+ * within PCIE_LINK_RETRAIN_TIMEOUT_MS milliseconds.
+ */
++int pcie_retrain_link(struct pci_dev *pdev, bool use_lt)
+ {
++ int rc;
+ u16 lnkctl;
+
++ /*
++ * Ensure the updated LNKCTL parameters are used during link
++ * training by checking that there is no ongoing link training to
++ * avoid LTSSM race as recommended in Implementation Note at the
++ * end of PCIe r6.0.1 sec 7.5.3.7.
++ */
++ rc = pcie_wait_for_link_status(pdev, use_lt, !use_lt);
++ if (rc)
++ return rc;
++
+ pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &lnkctl);
+ lnkctl |= PCI_EXP_LNKCTL_RL;
+ pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, lnkctl);
+ if (pdev->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.
+ */
+ lnkctl &= ~PCI_EXP_LNKCTL_RL;
+ pcie_capability_write_word(pdev, PCI_EXP_LNKCTL, lnkctl);
+ }
+
+ return pcie_wait_for_link_status(pdev, use_lt, !use_lt);
+ }
+
/**
* pcie_wait_for_link_delay - Wait until link is active or inactive
* @pdev: Bridge device
static bool pcie_wait_for_link_delay(struct pci_dev *pdev, bool active,
int delay)
{
- int timeout = 1000;
-- bool ret;
- u16 lnk_status;
++ int rc;
/*
* Some controllers might not implement link active reporting. In this
*/
if (active)
msleep(20);
- for (;;) {
- pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
- ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
- if (ret == active)
- break;
- if (timeout <= 0)
- break;
- msleep(10);
- timeout -= 10;
- }
- ret = pcie_wait_for_link_status(pdev, false, active);
- if (active && !ret)
- ret = pcie_failed_link_retrain(pdev);
-- if (active && ret)
++ rc = pcie_wait_for_link_status(pdev, false, active);
++ if (active) {
++ if (rc)
++ rc = pcie_failed_link_retrain(pdev);
++ if (rc)
++ return false;
++
msleep(delay);
- return ret;
++ return true;
++ }
+
- return ret == active;
++ if (rc)
++ return false;
+
++ return true;
}
/**
pci_ers_result_t (*reset_subordinates)(struct pci_dev *pdev));
bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
-bool pcie_retrain_link(struct pci_dev *pdev, bool use_lt);
++int pcie_retrain_link(struct pci_dev *pdev, bool use_lt);
#ifdef CONFIG_PCIEASPM
void pcie_aspm_init_link_state(struct pci_dev *pdev);
void pcie_aspm_exit_link_state(struct pci_dev *pdev);
reg16 &= ~PCI_EXP_LNKCTL_CCC;
pcie_capability_write_word(parent, PCI_EXP_LNKCTL, reg16);
- if (pcie_retrain_link(link)) {
- if (pcie_retrain_link(link->pdev, true))
- return;
++ if (pcie_retrain_link(link->pdev, true)) {
- /* Training failed. Restore common clock configurations */
- pci_err(parent, "ASPM: Could not configure common clock\n");
- list_for_each_entry(child, &linkbus->devices, bus_list)
- pcie_capability_write_word(child, PCI_EXP_LNKCTL,
+ /* Training failed. Restore common clock configurations */
+ pci_err(parent, "ASPM: Could not configure common clock\n");
+ list_for_each_entry(child, &linkbus->devices, bus_list)
+ pcie_capability_write_word(child, PCI_EXP_LNKCTL,
child_reg[PCI_FUNC(child->devfn)]);
- pcie_capability_write_word(parent, PCI_EXP_LNKCTL, parent_reg);
+ pcie_capability_write_word(parent, PCI_EXP_LNKCTL, parent_reg);
+ }
}
/* Convert L0s latency encoding to ns */
#include <linux/switchtec.h>
#include "pci.h"
- if (!pcie_retrain_link(dev, false)) {
+ /*
+ * Retrain the link of a downstream PCIe port by hand if necessary.
+ *
+ * This is needed at least where a downstream port of the ASMedia ASM2824
+ * Gen 3 switch is wired to the upstream port of the Pericom PI7C9X2G304
+ * Gen 2 switch, and observed with the Delock Riser Card PCI Express x1 >
+ * 2 x PCIe x1 device, P/N 41433, plugged into the SiFive HiFive Unmatched
+ * board.
+ *
+ * In such a configuration the switches are supposed to negotiate the link
+ * speed of preferably 5.0GT/s, falling back to 2.5GT/s. However the link
+ * continues switching between the two speeds indefinitely and the data
+ * link layer never reaches the active state, with link training reported
+ * repeatedly active ~84% of the time. Forcing the target link speed to
+ * 2.5GT/s with the upstream ASM2824 device makes the two switches talk to
+ * each other correctly however. And more interestingly retraining with a
+ * higher target link speed afterwards lets the two successfully negotiate
+ * 5.0GT/s.
+ *
+ * With the ASM2824 we can rely on the otherwise optional Data Link Layer
+ * Link Active status bit and in the failed link training scenario it will
+ * be off along with the Link Bandwidth Management Status indicating that
+ * hardware has changed the link speed or width in an attempt to correct
+ * unreliable link operation. For a port that has been left unconnected
+ * both bits will be clear. So use this information to detect the problem
+ * rather than polling the Link Training bit and watching out for flips or
+ * at least the active status.
+ *
+ * Since the exact nature of the problem isn't known and in principle this
+ * could trigger where an ASM2824 device is downstream rather upstream,
+ * apply this erratum workaround to any downstream ports as long as they
+ * support Link Active reporting and have the Link Control 2 register.
+ * Restrict the speed to 2.5GT/s then with the Target Link Speed field,
+ * request a retrain and wait 200ms for the data link to go up.
+ *
+ * If this turns out successful and we know by the Vendor:Device ID it is
+ * safe to do so, then lift the restriction, letting the devices negotiate
+ * a higher speed. Also check for a similar 2.5GT/s speed restriction the
+ * firmware may have already arranged and lift it with ports that already
+ * report their data link being up.
+ *
+ * Return TRUE if the link has been successfully retrained, otherwise FALSE.
+ */
+ bool pcie_failed_link_retrain(struct pci_dev *dev)
+ {
+ static const struct pci_device_id ids[] = {
+ { PCI_VDEVICE(ASMEDIA, 0x2824) }, /* ASMedia ASM2824 */
+ {}
+ };
+ u16 lnksta, lnkctl2;
+
+ if (!pci_is_pcie(dev) || !pcie_downstream_port(dev) ||
+ !pcie_cap_has_lnkctl2(dev) || !dev->link_active_reporting)
+ return false;
+
+ 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) {
+ pci_info(dev, "broken device, retraining non-functional downstream link at 2.5GT/s\n");
+
+ lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
+ lnkctl2 |= PCI_EXP_LNKCTL2_TLS_2_5GT;
+ pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, lnkctl2);
+
- if (!pcie_retrain_link(dev, false)) {
++ if (pcie_retrain_link(dev, false)) {
+ pci_info(dev, "retraining failed\n");
+ return false;
+ }
+
+ pcie_capability_read_word(dev, PCI_EXP_LNKSTA, &lnksta);
+ }
+
+ if ((lnksta & PCI_EXP_LNKSTA_DLLLA) &&
+ (lnkctl2 & PCI_EXP_LNKCTL2_TLS) == PCI_EXP_LNKCTL2_TLS_2_5GT &&
+ pci_match_id(ids, dev)) {
+ u32 lnkcap;
+
+ pci_info(dev, "removing 2.5GT/s downstream link speed restriction\n");
+ pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &lnkcap);
+ lnkctl2 &= ~PCI_EXP_LNKCTL2_TLS;
+ lnkctl2 |= lnkcap & PCI_EXP_LNKCAP_SLS;
+ pcie_capability_write_word(dev, PCI_EXP_LNKCTL2, lnkctl2);
+
++ if (pcie_retrain_link(dev, false)) {
+ pci_info(dev, "retraining failed\n");
+ return false;
+ }
+ }
+
+ return true;
+ }
+
static ktime_t fixup_debug_start(struct pci_dev *dev,
void (*fn)(struct pci_dev *dev))
{
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