linux-kernel - Re: drivers/pci/controller/cadence/pci-j721e.c:648:undefined reference to `cdns_pcie_host

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Message-ID: <wwgrzgcdqralnyrhvufoldiyautpkp2d2chveovgnen5qvt4p6@l6xdmkezpdd2>
Date: Wed, 12 Nov 2025 23:01:03 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Siddharth Vadapalli <s-vadapalli@...com>
Cc: kernel test robot <lkp@...el.com>, 
	Chen Wang <unicorn_wang@...look.com>, oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: drivers/pci/controller/cadence/pci-j721e.c:648:undefined
 reference to `cdns_pcie_host_disable'

On Tue, Nov 11, 2025 at 08:29:48PM +0530, Siddharth Vadapalli wrote:
> On 11/11/25 7:39 PM, Manivannan Sadhasivam wrote:
> > On Tue, Nov 11, 2025 at 05:09:25PM +0530, Siddharth Vadapalli wrote:
> > > On Tue, 2025-11-11 at 16:24 +0530, Manivannan Sadhasivam wrote:
> > > 
> > > Hello Mani,
> > > 
> > > > + Siddharth
> > > 
> > > Thank you for notifying me of this.
> > > 
> > > > 
> > > > On Tue, Nov 11, 2025 at 05:28:54PM +0800, kernel test robot wrote:
> > > > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > > > head:   4427259cc7f7571a157fbc9b5011e1ef6fe0a4a8
> > > > > commit: 1c72774df028429836eec3394212f2921bb830fc PCI: sg2042: Add Sophgo SG2042 PCIe driver
> > > > > date:   8 weeks ago
> > > > > config: loongarch-randconfig-r113-20251110 (https://download.01.org/0day-ci/archive/20251111/202511111705.MZ7ls8Hm-lkp@intel.com/config)
> > > > > compiler: loongarch64-linux-gcc (GCC) 15.1.0
> > > > > reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251111/202511111705.MZ7ls8Hm-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/202511111705.MZ7ls8Hm-lkp@intel.com/
> > > > > 
> > > > > All errors (new ones prefixed by >>):
> > > > > 
> > > > >     loongarch64-linux-ld: drivers/pci/controller/cadence/pci-j721e.o: in function `j721e_pcie_remove':
> > > > > > > drivers/pci/controller/cadence/pci-j721e.c:648:(.text+0x83c): undefined reference to `cdns_pcie_host_disable'
> > > > > 
> > > > 
> > > >  From .config:
> > > > 
> > > > CONFIG_PCIE_CADENCE=y
> > > > CONFIG_PCIE_CADENCE_HOST=m
> > > > CONFIG_PCIE_CADENCE_EP=y
> > > > CONFIG_PCIE_CADENCE_PLAT=y
> > > > # CONFIG_PCIE_CADENCE_PLAT_HOST is not set
> > > > CONFIG_PCIE_CADENCE_PLAT_EP=y
> > > > CONFIG_PCIE_SG2042_HOST=m
> > > > CONFIG_PCI_J721E=y
> > > > # CONFIG_PCI_J721E_HOST is not set
> > > > CONFIG_PCI_J721E_EP=y
> > > > 
> > > > PCI_J721E selects PCIE_CADENCE_HOST only if PCI_J721E_HOST is selected,
> > > > otherwise, it will not select it. This will take care of the dependency between
> > > > PCI_J721E and PCIE_CADENCE_{HOST/EP}.
> > > > 
> > > > But if PCIE_CADENCE_HOST is selected as a module by other drivers like,
> > > > CONFIG_PCIE_SG2042_HOST=m, then if PCI_J721E is selected as a built-in using
> > > > CONFIG_PCI_J721E_EP=y, it results in this build error as the built-in driver
> > > > becomes dependent on a symbol from a loadable module.
> > > 
> > > While I don't deny the build error associated with the above config, it is
> > > an invalid config in the sense that the Glue drivers for two different
> > > devices are being enabled. This seems to be a generic issue wherein
> > > multiple drivers tend to depend on a library/common driver. How is it
> > > handled in such cases?
> > 
> > AFAIK, the common library should be built-in to avoid issues like this.
> 
> Ok. If that is the usual approach then I have no objections to it.
> 
> > 
> > > Is there a notion of reordering configs to ensure that such build errors
> > > are avoided?
> > > 
> > > If PCI_J721E_EP was selected as 'y' before 'PCI_SG2042_HOST' being selected
> > > as 'm', it would have resulted in 'PCIE_CADENCE_EP' being selected as 'y'
> > > and this won't cause a build error even with 'PCI_SG2042_HOST' selected as
> > > 'm'.
> > > 
> > > > 
> > > > I guess, we should force PCIE_CADENCE_{HOST/EP} to be 'bool' as it is getting
> > > > selected by multiple drivers.
> > > 
> > > This will defeat the purpose of the series that enabled loadable module
> > > support for the pci-j721e.c driver and the pcie-cadence-host/ep.c drivers.
> > > 
> > 
> > Your 'pci-j721e.c' can still be a loadable module, only the common library will
> > be built-in, which is not that bad.
> 
> Yes, this will work.
> 
> Please let me know if you want me to post the patch to update
> CONFIG_PCIE_CADENCE_{EP/HOST} to a bool.
> 

Yes, please.

- Mani

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