PCI: cadence: Clear the ARI Capability Next Function Number of the last function

Next Function Number field in ARI Capability Register for last function
must be zero by default as per the PCIe specification, indicating there
is no next higher number function but that's not happening in our case,
so this patch clears the Next Function Number field for last function
used.

[kwilczynski: white spaces update for one define]
Link: https://lore.kernel.org/linux-pci/[email protected]
Signed-off-by: Jasko-EXT Wojciech <[email protected]>
Signed-off-by: Achal Verma <[email protected]>
Signed-off-by: Siddharth Vadapalli <[email protected]>
Signed-off-by: Krzysztof Wilczyński <[email protected]>
Reviewed-by: Vignesh Raghavendra <[email protected]>

Author: Jasko-EXT Wojciech

drivers/pci/controller/cadence/pcie-cadence-ep.c

@@ -565,14 +565,26 @@ static int cdns_pcie_ep_start(struct pci_epc *epc)
 	struct cdns_pcie *pcie = &ep->pcie;
 	struct device *dev = pcie->dev;
 	int max_epfs = sizeof(epc->function_num_map) * 8;
-	int ret, value, epf;
+	int ret, epf, last_fn;
+	u32 reg, value;
 
 	/*
 	 * BIT(0) is hardwired to 1, hence function 0 is always enabled
 	 * and can't be disabled anyway.
 	 */
 	cdns_pcie_writel(pcie, CDNS_PCIE_LM_EP_FUNC_CFG, epc->function_num_map);
 
+	/*
+	 * Next function field in ARI_CAP_AND_CTR register for last function
+	 * should be 0.
+	 * Clearing Next Function Number field for the last function used.
+	 */
+	last_fn = find_last_bit(&epc->function_num_map, BITS_PER_LONG);
+	reg     = CDNS_PCIE_CORE_PF_I_ARI_CAP_AND_CTRL(last_fn);
+	value  = cdns_pcie_readl(pcie, reg);
+	value &= ~CDNS_PCIE_ARI_CAP_NFN_MASK;
+	cdns_pcie_writel(pcie, reg, value);
+
 	if (ep->quirk_disable_flr) {
 		for (epf = 0; epf < max_epfs; epf++) {
 			if (!(epc->function_num_map & BIT(epf)))

drivers/pci/controller/cadence/pcie-cadence.h

@@ -130,6 +130,12 @@
 #define CDNS_PCIE_EP_FUNC_DEV_CAP_OFFSET	0xc0
 #define CDNS_PCIE_EP_FUNC_SRIOV_CAP_OFFSET	0x200
 
+/*
+ * Endpoint PF Registers
+ */
+#define CDNS_PCIE_CORE_PF_I_ARI_CAP_AND_CTRL(fn)	(0x144 + (fn) * 0x1000)
+#define CDNS_PCIE_ARI_CAP_NFN_MASK			GENMASK(15, 8)
+
 /*
  * Root Port Registers (PCI configuration space for the root port function)
  */