[HACK] msm: ipa: Enhance IPA_EMULATION guarding to avoid undefined re…

…ferences

When compiling the kernel using GCC LTO, we hit the following errors at link time:

/usr/lib/gcc/aarch64-linux-gnu/11.2.0/../../../../aarch64-linux-gnu/bin/ld: /tmp/cclIai5s.ltrans87.ltrans.o: in function `ipa_pci_remove':
<artificial>:(.text+0xfc): undefined reference to `ipa_ut_module_exit'
/usr/lib/gcc/aarch64-linux-gnu/11.2.0/../../../../aarch64-linux-gnu/bin/ld: /tmp/cclIai5s.ltrans87.ltrans.o: in function `ipa_pci_probe':
<artificial>:(.text+0x2310c): undefined reference to `ipa_ut_module_init'
collect2: error: ld returned 1 exit status
make[1]: *** [/home/0ctobot/Android/OnePlus/kebab/neutrino_kernel_oneplus_sm8250/Makefile:1211: vmlinux] Error 1
make: *** [Makefile:146: sub-make] Error 2

This seems to be a result of DCE, as these functions become
effectively unreachable with !CONFIG_IPA_UT and the compiler has
optimized out code for if-statements that it can prove are always
false.

This little hack may not jibe perfectly with what the original
author had in mind, but it's sufficient for our usecase.

Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>

drivers/platform/msm/Kconfig

@@ -199,7 +199,7 @@ config MSM_11AD
 
 config IPA_EMULATION
 	bool "IPA on X86 Linux (IPA emulation support)"
-	depends on X86 && IPA3
+	depends on X86 && IPA3 && IPA_UT
 	help
 	  This options is used only when building the X86 version of
 	  the IPA/GSI driver. On this mode, IPA driver will be probed

drivers/platform/msm/ipa/ipa_api.c

@@ -98,8 +98,6 @@
 
 #if defined(CONFIG_IPA_EMULATION)
 static bool running_emulation = true;
-#elif defined(CONFIG_PCI)
-static bool running_emulation;
 #endif
 
 static enum ipa_hw_type ipa_api_hw_type;
@@ -3196,7 +3194,7 @@ static const struct pci_error_handlers ipa_pci_err_handler = {
 	.resume = ipa_pci_io_resume,
 };
 
-static struct pci_driver ipa_pci_driver = {
+static struct pci_driver ipa_pci_driver __maybe_unused = {
 	.name     = ipa_pci_driver_name,
 	.id_table = ipa_pci_tbl,
 	.probe    = ipa_pci_probe,
@@ -3848,16 +3846,20 @@ static int ipa_pci_probe(
 	if (result && result != -EPROBE_DEFER)
 		pr_err("ipa: ipa3_pci_drv_probe failed\n");
 
+#if defined(CONFIG_IPA_EMULATION)
 	if (running_emulation)
 		ipa_ut_module_init();
+#endif
 
 	return result;
 }
 
 static void ipa_pci_remove(struct pci_dev *pci_dev)
 {
+#if defined(CONFIG_IPA_EMULATION)
 	if (running_emulation)
 		ipa_ut_module_exit();
+#endif
 }
 
 static void ipa_pci_shutdown(struct pci_dev *pci_dev)
@@ -3883,7 +3885,7 @@ static void ipa_pci_io_resume(struct pci_dev *pci_dev)
 static int __init ipa_module_init(void)
 {
 	pr_debug("IPA module init\n");
-#ifdef CONFIG_PCI
+#if defined(CONFIG_PCI) && defined(CONFIG_IPA_EMULATION)
 	if (running_emulation) {
 		/* Register as a PCI device driver */
 		return pci_register_driver(&ipa_pci_driver);