Re: [RFC PATCH 2/2] acpi/pci_root: negotiate CXL _OSC

[kernel test robot <lkp@intel.com>]

Hi Vishal,

[FYI, it's a private test report for your RFC patch.]
[auto build test WARNING on 74be98774dfbc5b8b795db726bd772e735d2edd4]

url:    https://github.com/0day-ci/linux/commits/Vishal-Verma/acpi-add-support-for-CXL-_OSC/20220317-082840
base:   74be98774dfbc5b8b795db726bd772e735d2edd4
config: x86_64-randconfig-a001 (https://download.01.org/0day-ci/archive/20220317/202203171123.Jy0945To-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project a6ec1e3d798f8eab43fb3a91028c6ab04e115fcb)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/8020d862c22d52b61a590343b2202e5d05332100
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Vishal-Verma/acpi-add-support-for-CXL-_OSC/20220317-082840
        git checkout 8020d862c22d52b61a590343b2202e5d05332100
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/acpi/

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> drivers/acpi/pci_root.c:562:3: warning: variable 'control' is uninitialized when used here [-Wuninitialized]
                   control |= OSC_CXL_ERROR_REPORTING_CONTROL;
                   ^~~~~~~
   drivers/acpi/pci_root.c:559:13: note: initialize the variable 'control' to silence this warning
           u32 control;
                      ^
                       = 0
>> drivers/acpi/pci_root.c:612:6: warning: variable 'cxl_support' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
           if (is_cxl(root)) {
               ^~~~~~~~~~~~
   drivers/acpi/pci_root.c:619:22: note: uninitialized use occurs here
                                             &cxl_control, cxl_support);
                                                           ^~~~~~~~~~~
   drivers/acpi/pci_root.c:612:2: note: remove the 'if' if its condition is always true
           if (is_cxl(root)) {
           ^~~~~~~~~~~~~~~~~~
   drivers/acpi/pci_root.c:588:17: note: initialize the variable 'cxl_support' to silence this warning
           u32 cxl_support, cxl_control = 0, cxl_requested = 0;
                          ^
                           = 0
   2 warnings generated.


vim +/control +562 drivers/acpi/pci_root.c

   556	
   557	static u32 calculate_cxl_control(void)
   558	{
   559		u32 control;
   560	
   561		if (pci_aer_available())
 > 562			control |= OSC_CXL_ERROR_REPORTING_CONTROL;
   563	
   564		return control;
   565	}
   566	
   567	static bool os_control_query_checks(struct acpi_pci_root *root, u32 support)
   568	{
   569		struct acpi_device *device = root->device;
   570	
   571		if (pcie_ports_disabled) {
   572			dev_info(&device->dev, "PCIe port services disabled; not requesting _OSC control\n");
   573			return false;
   574		}
   575	
   576		if ((support & ACPI_PCIE_REQ_SUPPORT) != ACPI_PCIE_REQ_SUPPORT) {
   577			decode_osc_support(root, "not requesting OS control; OS requires",
   578					   ACPI_PCIE_REQ_SUPPORT);
   579			return false;
   580		}
   581	
   582		return true;
   583	}
   584	
   585	static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
   586	{
   587		u32 support, control = 0, requested = 0;
   588		u32 cxl_support, cxl_control = 0, cxl_requested = 0;
   589		acpi_status status;
   590		struct acpi_device *device = root->device;
   591		acpi_handle handle = device->handle;
   592	
   593		/*
   594		 * Apple always return failure on _OSC calls when _OSI("Darwin") has
   595		 * been called successfully. We know the feature set supported by the
   596		 * platform, so avoid calling _OSC at all
   597		 */
   598		if (x86_apple_machine) {
   599			root->osc_control_set = ~OSC_PCI_EXPRESS_PME_CONTROL;
   600			decode_osc_control(root, "OS assumes control of",
   601					   root->osc_control_set);
   602			return;
   603		}
   604	
   605		support = calculate_support();
   606	
   607		decode_osc_support(root, "OS supports", support);
   608	
   609		if (os_control_query_checks(root, support))
   610			requested = control = calculate_control();
   611	
 > 612		if (is_cxl(root)) {
   613			cxl_support = calculate_cxl_support();
   614			decode_cxl_osc_support(root, "OS supports", cxl_support);
   615			cxl_requested = cxl_control = calculate_cxl_control();
   616		}
   617	
   618		status = acpi_pci_osc_control_set(handle, &control, support,
   619						  &cxl_control, cxl_support);
   620		if (ACPI_SUCCESS(status)) {
   621			if (control)
   622				decode_osc_control(root, "OS now controls", control);
   623			if (cxl_control)
   624				decode_cxl_osc_control(root, "OS now controls",
   625						   cxl_control);
   626	
   627			if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
   628				/*
   629				 * We have ASPM control, but the FADT indicates that
   630				 * it's unsupported. Leave existing configuration
   631				 * intact and prevent the OS from touching it.
   632				 */
   633				dev_info(&device->dev, "FADT indicates ASPM is unsupported, using BIOS configuration\n");
   634				*no_aspm = 1;
   635			}
   636		} else {
   637			/*
   638			 * We want to disable ASPM here, but aspm_disabled
   639			 * needs to remain in its state from boot so that we
   640			 * properly handle PCIe 1.1 devices.  So we set this
   641			 * flag here, to defer the action until after the ACPI
   642			 * root scan.
   643			 */
   644			*no_aspm = 1;
   645	
   646			/* _OSC is optional for PCI host bridges */
   647			if ((status == AE_NOT_FOUND) && !is_pcie(root))
   648				return;
   649	
   650			if (control) {
   651				decode_osc_control(root, "OS requested", requested);
   652				decode_osc_control(root, "platform willing to grant", control);
   653			}
   654			if (cxl_control) {
   655				decode_cxl_osc_control(root, "OS requested", cxl_requested);
   656				decode_cxl_osc_control(root, "platform willing to grant",
   657						   cxl_control);
   658			}
   659	
   660			dev_info(&device->dev, "_OSC: platform retains control of PCIe features (%s)\n",
   661				 acpi_format_exception(status));
   662		}
   663	}
   664	

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