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PCI: pnv_php: Work around switches with broken presence detection

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The Microsemi Switchtec PM8533 PFX 48xG3 [11f8:8533] PCIe switch system
was observed to incorrectly assert the Presence Detect Set bit in its
capabilities when tested on a Raptor Computing Systems Blackbird system,
resulting in the hot insert path never attempting a rescan of the bus
and any downstream devices not being re-detected.

Work around this by additionally checking whether the PCIe data link is
active or not when performing presence detection on downstream switches'
ports, similar to the pciehp_hpc.c driver.

Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com>
Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/505981576.1359853.1752615415117.JavaMail.zimbra@raptorengineeringinc.com
This commit is contained in:
Timothy Pearson
2025-07-15 16:36:55 -05:00
committed by Madhavan Srinivasan
parent 4668619092
commit 80f9fc2362
1 changed files with 27 additions and 0 deletions
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27
drivers/pci/hotplug/pnv_php.c
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@@ -391,6 +391,20 @@ static int pnv_php_get_power_state(struct hotplug_slot *slot, u8 *state)
return 0;
}
static int pcie_check_link_active(struct pci_dev *pdev)
{
u16 lnk_status;
int ret;
ret = pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnk_status);
if (ret == PCIBIOS_DEVICE_NOT_FOUND || PCI_POSSIBLE_ERROR(lnk_status))
return -ENODEV;
ret = !!(lnk_status & PCI_EXP_LNKSTA_DLLLA);
return ret;
}
static int pnv_php_get_adapter_state(struct hotplug_slot *slot, u8 *state)
{
struct pnv_php_slot *php_slot = to_pnv_php_slot(slot);
@@ -403,6 +417,19 @@ static int pnv_php_get_adapter_state(struct hotplug_slot *slot, u8 *state)
*/
ret = pnv_pci_get_presence_state(php_slot->id, &presence);
if (ret >= 0) {
if (pci_pcie_type(php_slot->pdev) == PCI_EXP_TYPE_DOWNSTREAM &&
presence == OPAL_PCI_SLOT_EMPTY) {
/*
* Similar to pciehp_hpc, check whether the Link Active
* bit is set to account for broken downstream bridges
* that don't properly assert Presence Detect State, as
* was observed on the Microsemi Switchtec PM8533 PFX
* [11f8:8533].
*/
if (pcie_check_link_active(php_slot->pdev) > 0)
presence = OPAL_PCI_SLOT_PRESENT;
}
*state = presence;
ret = 0;
} else {