linux-kernel - Re: [PATCH v5 4/4] PCI: keystone: Add support to build as a loadable module

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Message-ID: <fkzokskbjklt6atqrpwc46zsjr5ptpuynzhx4kvfurr4h37kae@rwcqljsjvzl6>
Date: Wed, 5 Nov 2025 22:53:44 +0530
From: Manivannan Sadhasivam <mani@...nel.org>
To: Siddharth Vadapalli <s-vadapalli@...com>
Cc: lpieralisi@...nel.org, kwilczynski@...nel.org, robh@...nel.org, 
	bhelgaas@...gle.com, jingoohan1@...il.com, christian.bruel@...s.st.com, 
	krishna.chundru@....qualcomm.com, qiang.yu@....qualcomm.com, shradha.t@...sung.com, 
	thippeswamy.havalige@....com, inochiama@...il.com, fan.ni@...sung.com, cassel@...nel.org, 
	kishon@...nel.org, 18255117159@....com, rongqianfeng@...o.com, jirislaby@...nel.org, 
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, srk@...com
Subject: Re: [PATCH v5 4/4] PCI: keystone: Add support to build as a loadable
 module

On Wed, Oct 29, 2025 at 01:34:52PM +0530, Siddharth Vadapalli wrote:
> The 'pci-keystone.c' driver is the application/glue/wrapper driver for the
> Designware PCIe Controllers on TI SoCs. Now that all of the helper APIs
> that the 'pci-keystone.c' driver depends upon have been exported for use,
> enable support to build the driver as a loadable module.
> 
> Additionally, the functions marked by the '__init' keyword may be invoked:
> a) After a probe deferral
> OR
> b) During a delayed probe - Delay attributed to driver being built as a
>    loadable module
> 
> In both of the cases mentioned above, the '__init' memory will be freed
> before the functions are invoked. This results in an exception of the form:
> 
> 	Unable to handle kernel paging request at virtual address ...
> 	Mem abort info:
> 	...
> 	pc : ks_pcie_host_init+0x0/0x540
> 	lr : dw_pcie_host_init+0x170/0x498
> 	...
> 	ks_pcie_host_init+0x0/0x540 (P)
> 	ks_pcie_probe+0x728/0x84c
> 	platform_probe+0x5c/0x98
> 	really_probe+0xbc/0x29c
> 	__driver_probe_device+0x78/0x12c
> 	driver_probe_device+0xd8/0x15c
> 	...
> 
> To address this, introduce a new function namely 'ks_pcie_init()' to
> register the 'fault handler' while removing the '__init' keyword from
> existing functions.
> 
> Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>
> ---
> 
> v4:
> https://lore.kernel.org/r/20251022095724.997218-5-s-vadapalli@ti.com/
> Changes since v4:
> - To fix the build error on ARM32 platforms as reported at:
>   https://lore.kernel.org/r/202510281008.jw19XuyP-lkp@intel.com/
>   patch 4 in the series has been updated by introducing a new config
>   named "PCI_KEYSTONE_TRISTATE" which allows building the driver as
>   a loadable module. Additionally, this newly introduced config can
>   be enabled only for non-ARM32 platforms. As a result, ARM32 platforms
>   continue using the existing PCI_KEYSTONE config which is a bool, while
>   ARM64 platforms can use PCI_KEYSTONE_TRISTATE which is a tristate, and
>   can optionally enabled loadable module support being enabled by this
>   series.
> 
> Regards,
> Siddharth.
> 
>  drivers/pci/controller/dwc/Kconfig        | 15 +++--
>  drivers/pci/controller/dwc/Makefile       |  3 +
>  drivers/pci/controller/dwc/pci-keystone.c | 78 +++++++++++++----------
>  3 files changed, 59 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
> index 349d4657393c..c5bc2f0b1f39 100644
> --- a/drivers/pci/controller/dwc/Kconfig
> +++ b/drivers/pci/controller/dwc/Kconfig
> @@ -482,15 +482,21 @@ config PCI_DRA7XX_EP
>  	  to enable device-specific features PCI_DRA7XX_EP must be selected.
>  	  This uses the DesignWare core.
>  
> +# ARM32 platforms use hook_fault_code() and cannot support loadable module.
>  config PCI_KEYSTONE
>  	bool
>  
> +# On non-ARM32 platforms, loadable module can be supported.
> +config PCI_KEYSTONE_TRISTATE
> +	tristate
> +
>  config PCI_KEYSTONE_HOST
> -	bool "TI Keystone PCIe controller (host mode)"
> +	tristate "TI Keystone PCIe controller (host mode)"
>  	depends on ARCH_KEYSTONE || ARCH_K3 || COMPILE_TEST
>  	depends on PCI_MSI
>  	select PCIE_DW_HOST
> -	select PCI_KEYSTONE
> +	select PCI_KEYSTONE if ARM
> +	select PCI_KEYSTONE_TRISTATE if !ARM

Wouldn't below change work for you?

diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
index 349d4657393c..b1219e7136c9 100644
--- a/drivers/pci/controller/dwc/Kconfig
+++ b/drivers/pci/controller/dwc/Kconfig
@@ -486,8 +486,9 @@ config PCI_KEYSTONE
        bool
 
 config PCI_KEYSTONE_HOST
-       bool "TI Keystone PCIe controller (host mode)"
+       tristate "TI Keystone PCIe controller (host mode)"
        depends on ARCH_KEYSTONE || ARCH_K3 || COMPILE_TEST
+       default y if ARCH_KEYSTONE
        depends on PCI_MSI
        select PCIE_DW_HOST
        select PCI_KEYSTONE

- Mani

-- 
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