[PATCH v2] powerpc/powernv: fix pci-cxl.c build when CONFIG_MODULES=n

["Ian Munsie" <imunsie@au1.ibm.com>]

From: Ian Munsie <imunsie@au1.ibm.com>

pnv_cxl_enable_phb_kernel_api() grabs a reference to the cxl module to
prevent it from being unloaded after the PHB has been switched to CX4 mode.
This breaks the build when CONFIG_MODULES=n as module_mutex doesn't exist.

However, if we don't have modules, we don't need to protect against the
case of the cxl module being unloaded. As such, split the relevant
code out into a function surrounded with #if IS_MODULE(CXL) so we don't try
to compile it if cxl isn't being compiled as a module.

Fixes: 5918dbc9b4ec ("powerpc/powernv: Add support for the cxl kernel api
on the real phb")
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>

---

Changes since v1:
	- Actually tested now our systems are back online
	- Passed error code back to caller
	- Fixed IS_MODULE(cxl) to IS_MODULE(CONFIG_CXL)
	- Face was introduced to palm, several times
---
 arch/powerpc/platforms/powernv/pci-cxl.c | 30 ++++++++++++++++++++++--------
 1 file changed, 22 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci-cxl.c b/arch/powerpc/platforms/powernv/pci-cxl.c
index 3f34207..2d67be0 100644
--- a/arch/powerpc/platforms/powernv/pci-cxl.c
+++ b/arch/powerpc/platforms/powernv/pci-cxl.c
@@ -166,6 +166,24 @@ int pnv_cxl_ioda_msi_setup(struct pci_dev *dev, unsigned int hwirq,
 }
 EXPORT_SYMBOL(pnv_cxl_ioda_msi_setup);
 
+#if IS_MODULE(CONFIG_CXL)
+static inline int get_cxl_module(void)
+{
+       struct module *cxl_module;
+
+       mutex_lock(&module_mutex);
+       cxl_module = find_module("cxl");
+       if (cxl_module)
+              __module_get(cxl_module);
+       mutex_unlock(&module_mutex);
+       if (!cxl_module)
+              return -ENODEV;
+       return 0;
+}
+#else
+static inline int get_cxl_module(void) { return 0; }
+#endif
+
 /*
  * Sets flags and switches the controller ops to enable the cxl kernel api.
  * Originally the cxl kernel API operated on a virtual PHB, but certain cards
@@ -175,7 +193,7 @@ EXPORT_SYMBOL(pnv_cxl_ioda_msi_setup);
 int pnv_cxl_enable_phb_kernel_api(struct pci_controller *hose, bool enable)
 {
 	struct pnv_phb *phb = hose->private_data;
-	struct module *cxl_module;
+	int rc;
 
 	if (!enable) {
 		/*
@@ -194,13 +212,9 @@ int pnv_cxl_enable_phb_kernel_api(struct pci_controller *hose, bool enable)
 	 * long as we are in this mode (and since we can't safely disable this
 	 * mode once enabled...).
 	 */
-	mutex_lock(&module_mutex);
-	cxl_module = find_module("cxl");
-	if (cxl_module)
-		__module_get(cxl_module);
-	mutex_unlock(&module_mutex);
-	if (!cxl_module)
-		return -ENODEV;
+	rc = get_cxl_module();
+	if (rc)
+		return rc;
 
 	phb->flags |= PNV_PHB_FLAG_CXL;
 	hose->controller_ops = pnv_cxl_cx4_ioda_controller_ops;
-- 
2.8.1