[PATCH v8 1/7] PCI/TPH: Fix pcie_tph_get_st_table_loc() field extraction

[Chengwen Feng <fengchengwen@huawei.com>]

pcie_tph_get_st_table_loc() incorrectly uses FIELD_GET(), which shifts the
field value to bit 0. But the function is designed to return raw
PCI_TPH_LOC_* values as defined in the function comment.

This causes incorrect ST table location detection. Fix it by using bitwise
AND with PCI_TPH_CAP_LOC_MASK to return the unshifted field value matching
the function specification.

This doesn't make a difference to mlx5_st_create(), the lone external
caller, because it only checks for PCI_TPH_LOC_NONE (0), but will be needed
for callers that check for PCI_TPH_LOC_CAP or PCI_TPH_LOC_MSIX.

Fixes: d2e8a34876ce ("PCI/TPH: Add Steering Tag support")
Cc: stable@vger.kernel.org
Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
Reviewed-by: Alex Williamson <alex.williamson@nvidia.com>
Reviewed-by: Bjorn Helgaas <bhelgaas@google.com>
---
 drivers/pci/tph.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
index 91145e8d9d95..877cf556242b 100644
--- a/drivers/pci/tph.c
+++ b/drivers/pci/tph.c
@@ -170,7 +170,7 @@ u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev)
 
 	pci_read_config_dword(pdev, pdev->tph_cap + PCI_TPH_CAP, &reg);
 
-	return FIELD_GET(PCI_TPH_CAP_LOC_MASK, reg);
+	return reg & PCI_TPH_CAP_LOC_MASK;
 }
 EXPORT_SYMBOL(pcie_tph_get_st_table_loc);
 
@@ -185,9 +185,6 @@ u16 pcie_tph_get_st_table_size(struct pci_dev *pdev)
 
 	/* Check ST table location first */
 	loc = pcie_tph_get_st_table_loc(pdev);
-
-	/* Convert loc to match with PCI_TPH_LOC_* defined in pci_regs.h */
-	loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
 	if (loc != PCI_TPH_LOC_CAP)
 		return 0;
 
@@ -316,8 +313,6 @@ int pcie_tph_set_st_entry(struct pci_dev *pdev, unsigned int index, u16 tag)
 	set_ctrl_reg_req_en(pdev, PCI_TPH_REQ_DISABLE);
 
 	loc = pcie_tph_get_st_table_loc(pdev);
-	/* Convert loc to match with PCI_TPH_LOC_* */
-	loc = FIELD_PREP(PCI_TPH_CAP_LOC_MASK, loc);
 
 	switch (loc) {
 	case PCI_TPH_LOC_MSIX:
-- 
2.17.1