Re: [PATCH v2 3/3] PCI: tegra194: Notify Endpoint functions on PERST# assert

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] PCI: tegra194: missing stub for pci_epc_linkdown() when !CONFIG_PCI_ENDPOINT
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commit 670ef998037ee122764995c2ef40bfe453687d53
Author: Manikanta Maddireddy <mmaddireddy@nvidia.com>

PCI: tegra194: Notify Endpoint functions on PERST# assert

This commit notifies endpoint function drivers of link down when the host
asserts reset in pex_ep_event_pex_rst_assert() before disabling the
controller. It calls pci_epc_linkdown() directly instead of
dw_pcie_ep_linkdown() to avoid reinitializing registers when the reference
clock may be unavailable.

> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> index 8cb907dbf6356..8dede9531956d 100644
> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> @@ -1704,6 +1704,9 @@ static void pex_ep_event_pex_rst_assert(struct tegra_pcie_dw *pcie)
>  	if (ret)
>  		dev_info(pcie->dev, "LTSSM state: 0x%x detect timeout: %d\n", val, ret);
>  
> +	/* Avoid the DBI register reinitialization in dw_pcie_ep_linkdown(). */
> +	pci_epc_linkdown(pcie->pci.ep.epc);

[Severity: Low]
Does calling pci_epc_linkdown() in pex_ep_event_pex_rst_assert() break the
build of drivers/pci/controller/dwc/pcie-tegra194.c when host mode is
enabled without endpoint support?

In drivers/pci/controller/dwc/Kconfig, host mode selects the common driver
without requiring endpoint support:

    config PCIE_TEGRA194_HOST
    	tristate "NVIDIA Tegra194 (and later) PCIe controller (host mode)"
    	depends on (ARCH_TEGRA && ARM64) || COMPILE_TEST
    	depends on PCI_MSI
    	select PCIE_DW_HOST
    	select PHY_TEGRA194_P2U
    	select PCIE_TEGRA194

In drivers/pci/controller/dwc/pcie-tegra194.c,
pex_ep_event_pex_rst_assert() is compiled unconditionally. However, in
include/linux/pci-epc.h, pci_epc_linkdown() is only declared inside the
endpoint guard and has no stub in the fallback block:

    #ifdef CONFIG_PCI_ENDPOINT
    ...
    void pci_epc_linkup(struct pci_epc *epc);
    void pci_epc_linkdown(struct pci_epc *epc);
    void pci_epc_init_notify(struct pci_epc *epc);
    void pci_epc_notify_pending_init(struct pci_epc *epc, struct pci_epf *epf);
    void pci_epc_deinit_notify(struct pci_epc *epc);
    ...
    #else
    static inline void pci_epc_init_notify(struct pci_epc *epc)
    {
    }

    static inline void pci_epc_deinit_notify(struct pci_epc *epc)
    {
    }
    #endif /* CONFIG_PCI_ENDPOINT */

Should a static inline stub for pci_epc_linkdown() be added to
include/linux/pci-epc.h so host-only configurations continue to build?

> +
>  	/*
>  	 * Deassert LTSSM state to stop the state toggling between
>  	 * Polling and Detect.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261021061903.1269605-1-mmaddireddy@nvidia.com?part=3