linux-kernel - Re: [PATCH v4 2/5] PCI/ERR: Add support for resetting the slots in a platform specific way

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Message-ID: <8899a562-2efd-9a63-5fc2-2972f47a9296@oss.qualcomm.com>
Date: Wed, 14 May 2025 12:03:16 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Oliver O'Halloran <oohall@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>, Zhou Wang <wangzhou1@...ilicon.com>,
        Will Deacon <will@...nel.org>, Robert Richter <rric@...nel.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Marc Zyngier <maz@...nel.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Daire McNamara <daire.mcnamara@...rochip.com>
Cc: dingwei@...vell.com, cassel@...nel.org, Lukas Wunner <lukas@...ner.de>,
        linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v4 2/5] PCI/ERR: Add support for resetting the slots in a
 platform specific way



On 5/8/2025 12:40 PM, Manivannan Sadhasivam wrote:
> Some host bridge devices require resetting the slots in a platform specific
> way to recover them from error conditions such as Fatal AER errors, Link
> Down etc... So introduce pci_host_bridge::reset_slot callback and call it
> from pcibios_reset_secondary_bus() if available.
> 
> The 'reset_slot' callback is responsible for resetting the given slot
> referenced by the 'pci_dev' pointer in a platform specific way and bring it
> back to the working state if possible. If any error occurs during the slot
> reset operation, relevant errno should be returned.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Reviewed-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>

- Krishna Chaitanya.
> ---
>   drivers/pci/pci.c      | 12 ++++++++++++
>   drivers/pci/pcie/err.c |  5 -----
>   include/linux/pci.h    |  1 +
>   3 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 4d7c9f64ea24ec754a135a2585c99489cfa641a9..13709bb898a967968540826a2b7ee8ade6b7e082 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4982,7 +4982,19 @@ void pci_reset_secondary_bus(struct pci_dev *dev)
>   
>   void __weak pcibios_reset_secondary_bus(struct pci_dev *dev)
>   {
> +	struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> +	int ret;
> +
> +	if (host->reset_slot) {
> +		ret = host->reset_slot(host, dev);
> +		if (ret)
> +			pci_err(dev, "failed to reset slot: %d\n", ret);
> +
> +		return;
> +	}
> +
>   	pci_reset_secondary_bus(dev);
> +
>   }
>   
>   /**
> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> index de6381c690f5c21f00021cdc7bde8d93a5c7db52..b834fc0d705938540d3d7d3d8739770c09fe7cf1 100644
> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -234,11 +234,6 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
>   	}
>   
>   	if (status == PCI_ERS_RESULT_NEED_RESET) {
> -		/*
> -		 * TODO: Should call platform-specific
> -		 * functions to reset slot before calling
> -		 * drivers' slot_reset callbacks?
> -		 */
>   		status = PCI_ERS_RESULT_RECOVERED;
>   		pci_dbg(bridge, "broadcast slot_reset message\n");
>   		pci_walk_bridge(bridge, report_slot_reset, &status);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 0e8e3fd77e96713054388bdc82f439e51023c1bf..8d7d2a49b76cf64b4218b179cec495e0d69ddf6f 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -599,6 +599,7 @@ struct pci_host_bridge {
>   	void (*release_fn)(struct pci_host_bridge *);
>   	int (*enable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
>   	void (*disable_device)(struct pci_host_bridge *bridge, struct pci_dev *dev);
> +	int (*reset_slot)(struct pci_host_bridge *bridge, struct pci_dev *dev);
>   	void		*release_data;
>   	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
>   	unsigned int	no_ext_tags:1;		/* No Extended Tags */
>