linux-kernel - Re: [PATCH 3/3] PCI: dwc: Skip PME_Turn_Off and L2/L3 transition if no device is available

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Message-ID: <202511071025.JM5nTGnO-lkp@intel.com>
Date: Fri, 7 Nov 2025 11:28:26 +0800
From: kernel test robot <lkp@...el.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>,
	lpieralisi@...nel.org, kwilczynski@...nel.org, mani@...nel.org,
	bhelgaas@...gle.com
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev, will@...nel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	robh@...nel.org, linux-arm-msm@...r.kernel.org,
	zhangsenchuan@...incomputing.com,
	Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
Subject: Re: [PATCH 3/3] PCI: dwc: Skip PME_Turn_Off and L2/L3 transition if
 no device is available

Hi Manivannan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on pci/next]
[also build test WARNING on pci/for-linus linus/master v6.18-rc4 next-20251106]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Manivannan-Sadhasivam/PCI-host-common-Add-an-API-to-check-for-any-device-under-the-Root-Ports/20251106-141822
base:   https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git next
patch link:    https://lore.kernel.org/r/20251106061326.8241-4-manivannan.sadhasivam%40oss.qualcomm.com
patch subject: [PATCH 3/3] PCI: dwc: Skip PME_Turn_Off and L2/L3 transition if no device is available
config: arm-randconfig-001-20251107 (https://download.01.org/0day-ci/archive/20251107/202511071025.JM5nTGnO-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251107/202511071025.JM5nTGnO-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511071025.JM5nTGnO-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/pci/controller/dwc/pcie-designware-host.c:1133:6: warning: variable 'ret' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
    1133 |         if (!pci_root_ports_have_device(pci->pp.bridge->bus))
         |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/pci/controller/dwc/pcie-designware-host.c:1176:9: note: uninitialized use occurs here
    1176 |         return ret;
         |                ^~~
   drivers/pci/controller/dwc/pcie-designware-host.c:1133:2: note: remove the 'if' if its condition is always false
    1133 |         if (!pci_root_ports_have_device(pci->pp.bridge->bus))
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    1134 |                 goto stop_link;
         |                 ~~~~~~~~~~~~~~
   drivers/pci/controller/dwc/pcie-designware-host.c:1131:9: note: initialize the variable 'ret' to silence this warning
    1131 |         int ret;
         |                ^
         |                 = 0
   1 warning generated.


vim +1133 drivers/pci/controller/dwc/pcie-designware-host.c

  1126	
  1127	int dw_pcie_suspend_noirq(struct dw_pcie *pci)
  1128	{
  1129		u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
  1130		u32 val;
  1131		int ret;
  1132	
> 1133		if (!pci_root_ports_have_device(pci->pp.bridge->bus))
  1134			goto stop_link;
  1135	
  1136		/*
  1137		 * If L1SS is supported, then do not put the link into L2 as some
  1138		 * devices such as NVMe expect low resume latency.
  1139		 */
  1140		if (dw_pcie_readw_dbi(pci, offset + PCI_EXP_LNKCTL) & PCI_EXP_LNKCTL_ASPM_L1)
  1141			return 0;
  1142	
  1143		if (pci->pp.ops->pme_turn_off) {
  1144			pci->pp.ops->pme_turn_off(&pci->pp);
  1145		} else {
  1146			ret = dw_pcie_pme_turn_off(pci);
  1147			if (ret)
  1148				return ret;
  1149		}
  1150	
  1151		ret = read_poll_timeout(dw_pcie_get_ltssm, val,
  1152					val == DW_PCIE_LTSSM_L2_IDLE ||
  1153					val <= DW_PCIE_LTSSM_DETECT_WAIT,
  1154					PCIE_PME_TO_L2_TIMEOUT_US/10,
  1155					PCIE_PME_TO_L2_TIMEOUT_US, false, pci);
  1156		if (ret) {
  1157			/* Only log message when LTSSM isn't in DETECT or POLL */
  1158			dev_err(pci->dev, "Timeout waiting for L2 entry! LTSSM: 0x%x\n", val);
  1159			return ret;
  1160		}
  1161	
  1162		/*
  1163		 * Per PCIe r6.0, sec 5.3.3.2.1, software should wait at least
  1164		 * 100ns after L2/L3 Ready before turning off refclock and
  1165		 * main power. This is harmless when no endpoint is connected.
  1166		 */
  1167		udelay(1);
  1168	
  1169	stop_link:
  1170		dw_pcie_stop_link(pci);
  1171		if (pci->pp.ops->deinit)
  1172			pci->pp.ops->deinit(&pci->pp);
  1173	
  1174		pci->suspended = true;
  1175	
  1176		return ret;
  1177	}
  1178	EXPORT_SYMBOL_GPL(dw_pcie_suspend_noirq);
  1179	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki