PCI: endpoint: Align pci_epc_set_msi(), pci_epc_ops::set_msi() nr_irqs encoding

The kdoc for pci_epc_set_msi() says:
"Invoke to set the required number of MSI interrupts."

The kdoc for the callback pci_epc_ops::set_msi() says:
"ops to set the requested number of MSI interrupts in the MSI capability
register"

pci_epc_ops::set_msi() does however expect the parameter 'interrupts' to be
in the encoding as defined by the Multiple Message Capable (MMC) field of
the MSI capability structure. Nowhere in the kdoc does it say that the
number of interrupts should be in MMC encoding.

It is very confusing that the API pci_epc_set_msi() and the callback
function pci_epc_ops::set_msi() both take a parameter named 'interrupts',
but they expect completely different encodings.

Clean up the API and the callback function to have the same semantics,
i.e. the parameter represents the number of interrupts, regardless of the
internal encoding of that value.

Also rename the parameter 'interrupts' to 'nr_irqs', in both the wrapper
function and the callback function, such that the name is unambiguous.

[bhelgaas: more specific subject]

Signed-off-by: Niklas Cassel <cassel@kernel.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable+noautosel@kernel.org # this is simply a cleanup
Link: https://patch.msgid.link/20250514074313.283156-13-cassel@kernel.org

4 files changed, 11 insertions, 8 deletions

diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
index 569cb7481d45..f09f29ed27ed 100644
--- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
+++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
@@ -220,10 +220,11 @@ static void cdns_pcie_ep_unmap_addr(struct pci_epc *epc, u8 fn, u8 vfn,
 	clear_bit(r, &ep->ob_region_map);
 }
 
-static int cdns_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn, u8 mmc)
+static int cdns_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn, u8 nr_irqs)
 {
 	struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
 	struct cdns_pcie *pcie = &ep->pcie;
+	u8 mmc = order_base_2(nr_irqs);
 	u32 cap = CDNS_PCIE_EP_FUNC_MSI_CAP_OFFSET;
 	u16 flags;
 
diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 307c862588a4..230e82674591 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -536,11 +536,12 @@ static int dw_pcie_ep_get_msi(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
 }
 
 static int dw_pcie_ep_set_msi(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
-			      u8 interrupts)
+			      u8 nr_irqs)
 {
 	struct dw_pcie_ep *ep = epc_get_drvdata(epc);
 	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
 	struct dw_pcie_ep_func *ep_func;
+	u8 mmc = order_base_2(nr_irqs);
 	u32 val, reg;
 
 	ep_func = dw_pcie_ep_get_func_from_ep(ep, func_no);
@@ -550,7 +551,7 @@ static int dw_pcie_ep_set_msi(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
 	reg = ep_func->msi_cap + PCI_MSI_FLAGS;
 	val = dw_pcie_ep_readw_dbi(ep, func_no, reg);
 	val &= ~PCI_MSI_FLAGS_QMASK;
-	val |= FIELD_PREP(PCI_MSI_FLAGS_QMASK, interrupts);
+	val |= FIELD_PREP(PCI_MSI_FLAGS_QMASK, mmc);
 	dw_pcie_dbi_ro_wr_en(pci);
 	dw_pcie_ep_writew_dbi(ep, func_no, reg, val);
 	dw_pcie_dbi_ro_wr_dis(pci);
diff --git a/drivers/pci/controller/pcie-rcar-ep.c b/drivers/pci/controller/pcie-rcar-ep.c
index 9da39a4617b6..a8a966844cf3 100644
--- a/drivers/pci/controller/pcie-rcar-ep.c
+++ b/drivers/pci/controller/pcie-rcar-ep.c
@@ -256,15 +256,15 @@ static void rcar_pcie_ep_clear_bar(struct pci_epc *epc, u8 fn, u8 vfn,
 	clear_bit(atu_index + 1, ep->ib_window_map);
 }
 
-static int rcar_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn,
-				u8 interrupts)
+static int rcar_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn, u8 nr_irqs)
 {
 	struct rcar_pcie_endpoint *ep = epc_get_drvdata(epc);
 	struct rcar_pcie *pcie = &ep->pcie;
+	u8 mmc = order_base_2(nr_irqs);
 	u32 flags;
 
 	flags = rcar_pci_read_reg(pcie, MSICAP(fn));
-	flags |= interrupts << MSICAP0_MMESCAP_OFFSET;
+	flags |= mmc << MSICAP0_MMESCAP_OFFSET;
 	rcar_pci_write_reg(pcie, flags, MSICAP(fn));
 
 	return 0;
diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
index 85ca7d9b4c77..a0a85080c31d 100644
--- a/drivers/pci/controller/pcie-rockchip-ep.c
+++ b/drivers/pci/controller/pcie-rockchip-ep.c
@@ -308,10 +308,11 @@ static void rockchip_pcie_ep_unmap_addr(struct pci_epc *epc, u8 fn, u8 vfn,
 }
 
 static int rockchip_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn,
-				    u8 multi_msg_cap)
+				    u8 nr_irqs)
 {
 	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
 	struct rockchip_pcie *rockchip = &ep->rockchip;
+	u8 mmc = order_base_2(nr_irqs);
 	u32 flags;
 
 	flags = rockchip_pcie_read(rockchip,
@@ -319,7 +320,7 @@ static int rockchip_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn,
 				   ROCKCHIP_PCIE_EP_MSI_CTRL_REG);
 	flags &= ~ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_MASK;
 	flags |=
-	   (multi_msg_cap << ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET) |
+	   (mmc << ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET) |
 	   (PCI_MSI_FLAGS_64BIT << ROCKCHIP_PCIE_EP_MSI_FLAGS_OFFSET);
 	flags &= ~ROCKCHIP_PCIE_EP_MSI_CTRL_MASK_MSI_CAP;
 	rockchip_pcie_write(rockchip, flags,