Re: [PATCH v6 2/3] PCI: cadence: Add HPA IP debugfs for LTSSM status

[Aksh Garg]

On 19/05/26 18:06, Hans Zhang wrote:
> Add debugfs support for HPA-based Cadence PCIe controllers. A new file
> 'ltssm_status' is created under debugfs, allowing users to read the
> current LTSSM state as a string and raw value.
>
> Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
> ---
>   Documentation/ABI/testing/debugfs-cdns-pcie   |   5 +
>   drivers/pci/controller/cadence/Kconfig        |   9 +
>   drivers/pci/controller/cadence/Makefile       |   1 +
>   drivers/pci/controller/cadence/pci-sky1.c     |   4 +
>   .../controller/cadence/pcie-cadence-debugfs.c | 208 ++++++++++++++++++
>   .../cadence/pcie-cadence-host-hpa.c           |  19 +-
>   drivers/pci/controller/cadence/pcie-cadence.h | 153 +++++++++++++
>   7 files changed, 398 insertions(+), 1 deletion(-)
>   create mode 100644 Documentation/ABI/testing/debugfs-cdns-pcie
>   create mode 100644 drivers/pci/controller/cadence/pcie-cadence-debugfs.c
>
> diff --git a/Documentation/ABI/testing/debugfs-cdns-pcie b/Documentation/ABI/testing/debugfs-cdns-pcie
> new file mode 100644
> index 000000000000..c1104e28e4ee
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-cdns-pcie
> @@ -0,0 +1,5 @@
> +What:		/sys/kernel/debug/cdns_pcie_<dev>/ltssm_status
> +Date:		March 2026
> +Contact:	Hans Zhang <18255117159@xxxxxxx>
> +Description:	(RO) Read will return the current PCIe LTSSM state in both
> +		string and raw value.
> \ No newline at end of file
> diff --git a/drivers/pci/controller/cadence/Kconfig b/drivers/pci/controller/cadence/Kconfig
> index 9e651d545973..cb010bc97aad 100644
> --- a/drivers/pci/controller/cadence/Kconfig
> +++ b/drivers/pci/controller/cadence/Kconfig
> @@ -6,6 +6,15 @@ menu "Cadence-based PCIe controllers"
>   config PCIE_CADENCE
>   	tristate
>   
> +config PCIE_CADENCE_DEBUGFS
> +	tristate "Cadence PCIe debugfs entries"
> +	depends on DEBUG_FS
> +	depends on PCIE_CADENCE_HOST || PCIE_CADENCE_EP
> +	help
> +	  Say Y here to enable debugfs entries for the PCIe controller. These
> +	  entries provide various debug features related to the controller and
> +	  the LTSSM status of link can be displayed.
> +
>   config PCIE_CADENCE_HOST
>   	tristate
>   	depends on OF

Sashiko pointed the compilation issues when this is build as a module.
The linkage issue needs to be resolved if we want this as a module.
Also, if we build it as m, it would requires MODULE_LICENSE() and 
MODULE_DESCRIPTION().

> diff --git a/drivers/pci/controller/cadence/Makefile b/drivers/pci/controller/cadence/Makefile
> index b8ec1cecfaa8..2cdc4617e0c2 100644
> --- a/drivers/pci/controller/cadence/Makefile
> +++ b/drivers/pci/controller/cadence/Makefile
> @@ -4,6 +4,7 @@ pcie-cadence-host-mod-y := pcie-cadence-host-common.o pcie-cadence-host.o pcie-c
>   pcie-cadence-ep-mod-y := pcie-cadence-ep.o
>   
>   obj-$(CONFIG_PCIE_CADENCE) = pcie-cadence-mod.o
> +obj-$(CONFIG_PCIE_CADENCE_DEBUGFS) += pcie-cadence-debugfs.o
>   obj-$(CONFIG_PCIE_CADENCE_HOST) += pcie-cadence-host-mod.o
>   obj-$(CONFIG_PCIE_CADENCE_EP) += pcie-cadence-ep-mod.o
>   obj-$(CONFIG_PCIE_CADENCE_PLAT) += pcie-cadence-plat.o
> diff --git a/drivers/pci/controller/cadence/pci-sky1.c b/drivers/pci/controller/cadence/pci-sky1.c
> index e1f4a98e2ab6..b8632f1d3156 100644
> --- a/drivers/pci/controller/cadence/pci-sky1.c
> +++ b/drivers/pci/controller/cadence/pci-sky1.c
> @@ -221,6 +221,10 @@ MODULE_DEVICE_TABLE(of, of_sky1_pcie_match);

[ ... ]

>   /**
> @@ -447,6 +583,7 @@ void cdns_pcie_host_disable(struct cdns_pcie_rc *rc);
>   void __iomem *cdns_pci_map_bus(struct pci_bus *bus, unsigned int devfn,
>   			       int where);
>   int cdns_pcie_hpa_host_setup(struct cdns_pcie_rc *rc);
> +void cdns_pcie_hpa_host_disable(struct cdns_pcie_rc *rc);
>   #else
>   static inline int cdns_pcie_host_link_setup(struct cdns_pcie_rc *rc)
>   {
> @@ -472,6 +609,10 @@ static inline void cdns_pcie_host_disable(struct cdns_pcie_rc *rc)
>   {
>   }
>   
> +static inline void cdns_pcie_hpa_host_disable(struct cdns_pcie_rc *rc)
> +{
> +}
> +
>   static inline void __iomem *cdns_pci_map_bus(struct pci_bus *bus, unsigned int devfn,
>   					     int where)
>   {
> @@ -535,4 +676,16 @@ bool cdns_pcie_hpa_link_up(struct cdns_pcie *pcie);
>   
>   extern const struct dev_pm_ops cdns_pcie_pm_ops;
>   
> +#ifdef CONFIG_PCIE_CADENCE_DEBUGFS

Use "#if IS_ENABLED(CONFIG_PCIE_CADENCE_DEBUGFS)" to resolve the 
compilation error when building as a module.

> +void cdns_pcie_debugfs_deinit(struct cdns_pcie *pci);
> +void cdns_pcie_debugfs_init(struct cdns_pcie *pci);
> +#else
> +static inline void cdns_pcie_debugfs_deinit(struct cdns_pcie *pci)
> +{
> +}
> +static inline void cdns_pcie_debugfs_init(struct cdns_pcie *pci)
> +{
> +}
> +#endif
> +
>   #endif /* _PCIE_CADENCE_H */