Fix find_first_zero_bit() usage

find_first_zero_bit()'s parameter 'size' is defined in bits, not in bytes.

find_first_zero_bit() was called with size in bytes rather than bits, which thus defined a too low upper limit, causing dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4 and bar 5, which made bar 5 overwrite the settings set by bar 4.

Fix this by using replacing find_first_zero_bit() with ffz(), since ffz() only works on a single 'unsigned long' and therefore does not need a size argument.

Fixes f8aed6ec624f ("PCI: dwc: designware: Add EP mode support")

Signed-off-by Niklas Cassel <[email protected]>

---
 drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

drivers/pci/dwc/pcie-designware-ep.c +0 -0

index d53d5f168363..ab9a9e160daf 100644

drivers/pci/dwc/pcie-designware-ep.c +1 -2

 	if (free_win >= ep->num_ib_windows) {
 		dev_err(pci->dev, "no free inbound window\n");
 		return -EINVAL;

@@ -96,8 +95,7 @@ static int dw_pcie_ep_outbound_atu(struct dw_pcie_ep *ep, phys_addr_t phys_addr,
 	u32 free_win;
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	free_win = find_first_zero_bit(&ep->ob_window_map,
-				       sizeof(ep->ob_window_map));
+	free_win = ffz(ep->ob_window_map);
 	if (free_win >= ep->num_ob_windows) {
 		dev_err(pci->dev, "no free outbound window\n");
 		return -EINVAL;

Signature · 1 line

2.14.2

[+Kishon - please CC him next time]

Quoted 23 lines · Niklas Cassel

find_first_zero_bit()'s parameter 'size' is defined in bits, not in bytes.

find_first_zero_bit() was called with size in bytes rather than bits, which thus defined a too low upper limit, causing dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4 and bar 5, which made bar 5 overwrite the settings set by bar 4.

Fix this by using replacing find_first_zero_bit() with ffz(), since ffz() only works on a single 'unsigned long' and therefore does not need a size argument.

Fixes f8aed6ec624f ("PCI: dwc: designware: Add EP mode support")

Signed-off-by Niklas Cassel <[email protected]>

---
 drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

drivers/pci/dwc/pcie-designware-ep.c +0 -0

index d53d5f168363..ab9a9e160daf 100644

drivers/pci/dwc/pcie-designware-ep.c static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar, · line 73

Quoted 6 lines

drivers/pci/dwc/pcie-designware-ep.c +1 -2

@@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar,
 	u32 free_win;
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	free_win = find_first_zero_bit(&ep->ib_window_map,
-				       sizeof(ep->ib_window_map));
+	free_win = ffz(ep->ib_window_map);

You fix the bug at hand but code suffers from the same issue since we should be checking the value against ~0UL first ie if size in bits < num_ib_windows (that I think it is unlikely anyway but while at it let's think if we can improve this).

@Kishon: maybe we should add a static upper size and declare a static bitmap accordingly (and still use find_first_zero_bit()) ?

I think the check against ~0UL should be added anyway, let's get Kishon's opinion before a v3 (if any).

Hi Lorenzo,

Quoted 38 lines · Lorenzo Pieralisi

[+Kishon - please CC him next time]

Quoted 23 lines · Niklas Cassel

find_first_zero_bit()'s parameter 'size' is defined in bits, not in bytes.

find_first_zero_bit() was called with size in bytes rather than bits, which thus defined a too low upper limit, causing dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4 and bar 5, which made bar 5 overwrite the settings set by bar 4.

Fix this by using replacing find_first_zero_bit() with ffz(), since ffz() only works on a single 'unsigned long' and therefore does not need a size argument.

Fixes f8aed6ec624f ("PCI: dwc: designware: Add EP mode support")

Signed-off-by Niklas Cassel <[email protected]>

---
 drivers/pci/dwc/pcie-designware-ep.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

drivers/pci/dwc/pcie-designware-ep.c +0 -0

index d53d5f168363..ab9a9e160daf 100644

drivers/pci/dwc/pcie-designware-ep.c static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar, · line 73

Quoted 6 lines

drivers/pci/dwc/pcie-designware-ep.c +1 -2

@@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar,
 	u32 free_win;
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 
-	free_win = find_first_zero_bit(&ep->ib_window_map,
-				       sizeof(ep->ib_window_map));
+	free_win = ffz(ep->ib_window_map);

You fix the bug at hand but code suffers from the same issue since we should be checking the value against ~0UL first ie if size in bits < num_ib_windows (that I think it is unlikely anyway but while at it let's think if we can improve this).

Quoted 5 lines

@Kishon: maybe we should add a static upper size and declare a static bitmap accordingly (and still use find_first_zero_bit()) ?

I think the check against ~0UL should be added anyway, let's get Kishon's opinion before a v3 (if any).

Yeah, for both ffz and find_first_zero_bit, the results are undefined if no zero exists.

I'm thinking if we should just use find_first_zero_bit(&ep->ib_window_map, ep->num_ib_windows) after checking if there are some '0' bits left.