linux-kernel - Re: [PATCH v6 1/4] PCI/ERR: Add support for resetting the Root Ports in a platform specific wayy

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Message-ID: <aHlAw2rS8RcrqrE1@lizhi-Precision-Tower-5810>
Date: Thu, 17 Jul 2025 14:28:19 -0400
From: Frank Li <Frank.li@....com>
To: manivannan.sadhasivam@....qualcomm.com
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
	Oliver O'Halloran <oohall@...il.com>, Will Deacon <will@...nel.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
	Philipp Zabel <p.zabel@...gutronix.de>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
	linux-rockchip@...ts.infradead.org,
	Niklas Cassel <cassel@...nel.org>,
	Wilfred Mallawa <wilfred.mallawa@....com>,
	Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
	Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v6 1/4] PCI/ERR: Add support for resetting the Root Ports
 in a platform specific wayy

On Tue, Jul 15, 2025 at 07:51:04PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> From: Manivannan Sadhasivam <mani@...nel.org>
>
> Some host bridge devices require resetting the Root Ports 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_root_port()
> callback and call it from pcibios_reset_secondary_bus() if available. Also,
> save the Root Port config space before reset and restore it afterwards.
>
> The 'reset_root_port' callback is responsible for resetting the given Root
> Port 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 reset operation, relevant errno should be returned.

Reviewed-by: Frank Li <Frank.Li@....com>

>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@....qualcomm.com>
> ---
>  drivers/pci/pci.c      | 20 ++++++++++++++++++++
>  drivers/pci/pcie/err.c |  5 -----
>  include/linux/pci.h    |  1 +
>  3 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index e9448d55113bdfd2263d8e2f6b3ec802f56b712e..b29264aa2be33b18a58b3b3db1d1fb0f6483e5e8 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -4964,6 +4964,26 @@ 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 (pci_is_root_bus(dev->bus) && host->reset_root_port) {
> +		/*
> +		 * Save the config space of the Root Port before doing the
> +		 * reset, since the state could be lost. The Endpoint state
> +		 * should've been saved by the caller.
> +		 */
> +		pci_save_state(dev);
> +		ret = host->reset_root_port(host, dev);
> +		if (ret)
> +			pci_err(dev, "Failed to reset Root Port: %d\n", ret);
> +		else
> +			/* Now restore it on success */
> +			pci_restore_state(dev);
> +
> +		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 05e68f35f39238f8b9ce08df97b384d1c1e89bbe..e7c118a961910a307ec365f17b8fe4f2585267e8 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_root_port)(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 */
>
> --
> 2.45.2
>
>