fpga: altera-cvp: Fix registration for CvP incapable devices

[ Upstream commit 68f60538daa4bc3da5d0764d46f391916fba20fd ]

The probe function needs to verify the CvP enable bit in order to
properly determine if FPGA Manager functionality can be safely
enabled.

Fixes: 34d1dc17ce97 ("fpga manager: Add Altera CvP driver")
Signed-off-by: Andreas Puhm <puhm@oregano.at>
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Reviewed-by: Moritz Fischer <mdf@kernel.org>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/fpga/altera-cvp.c

@@ -403,6 +403,7 @@ static int altera_cvp_probe(struct pci_dev *pdev,
 	struct altera_cvp_conf *conf;
 	struct fpga_manager *mgr;
 	u16 cmd, val;
+	u32 regval;
 	int ret;
 
 	/*
@@ -416,6 +417,14 @@ static int altera_cvp_probe(struct pci_dev *pdev,
 		return -ENODEV;
 	}
 
+	pci_read_config_dword(pdev, VSE_CVP_STATUS, &regval);
+	if (!(regval & VSE_CVP_STATUS_CVP_EN)) {
+		dev_err(&pdev->dev,
+			"CVP is disabled for this device: CVP_STATUS Reg 0x%x\n",
+			regval);
+		return -ENODEV;
+	}
+
 	conf = devm_kzalloc(&pdev->dev, sizeof(*conf), GFP_KERNEL);
 	if (!conf)
 		return -ENOMEM;