linux-kernel - Re: [PATCH v2 3/4] PCI: Add link down handling for host bridges

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Message-ID: <doyt4kcaffgjm5u5notcjnqur7ydim3dpo4se5em2an36wa3rp@xzntx4sa47dl>
Date: Thu, 17 Apr 2025 13:12:08 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Lukas Wunner <lukas@...ner.de>
Cc: Mahesh J Salgaonkar <mahesh@...ux.ibm.com>, 
	Oliver O'Halloran <oohall@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczy??ski <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, dingwei@...vell.com, cassel@...nel.org, 
	Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>, linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 3/4] PCI: Add link down handling for host bridges

On Wed, Apr 16, 2025 at 06:57:11PM +0200, Lukas Wunner wrote:
> On Wed, Apr 16, 2025 at 09:59:05PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> > --- a/drivers/pci/pcie/err.c
> > +++ b/drivers/pci/pcie/err.c
> > @@ -270,3 +270,30 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> >  
> >  	return status;
> >  }
> > +
> > +static pci_ers_result_t pcie_do_slot_reset(struct pci_dev *dev)
> > +{
> > +	int ret;
> > +
> > +	ret = pci_bus_error_reset(dev);
> > +	if (ret) {
> > +		pci_err(dev, "Failed to reset slot: %d\n", ret);
> > +		return PCI_ERS_RESULT_DISCONNECT;
> > +	}
> > +
> > +	pci_info(dev, "Slot has been reset\n");
> > +
> > +	return PCI_ERS_RESULT_RECOVERED;
> > +}
> > +
> > +void pcie_do_recover_slots(struct pci_host_bridge *host)
> > +{
> > +	struct pci_bus *bus = host->bus;
> > +	struct pci_dev *dev;
> > +
> > +	for_each_pci_bridge(dev, bus) {
> > +		if (pci_is_root_bus(bus))
> > +			pcie_do_recovery(dev, pci_channel_io_frozen,
> > +					 pcie_do_slot_reset);
> > +	}
> > +}
> 
> Since pcie_do_slot_reset(), pcie_do_recover_slots() and
> pcie_do_recover_slots() are only needed on platforms with a
> specific host controller (and not, say, on x86), it would be good
> if they could be kept e.g. in a library in drivers/pci/controller/
> to avoid unnecessarily enlarging the .text section for everyone else.
> 
> One option would be the existing pci-host-common.c, another a
> completely new file.
> 

I don't like introducing a new file, so I'll make pci-host-common as a common
library for host controller drivers and move this code there.

> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -966,6 +966,7 @@ int pci_aer_clear_status(struct pci_dev *dev);
> >  int pci_aer_raw_clear_status(struct pci_dev *dev);
> >  void pci_save_aer_state(struct pci_dev *dev);
> >  void pci_restore_aer_state(struct pci_dev *dev);
> > +void pcie_do_recover_slots(struct pci_host_bridge *host);
> >  #else
> >  static inline void pci_no_aer(void) { }
> >  static inline void pci_aer_init(struct pci_dev *d) { }
> > @@ -975,6 +976,26 @@ static inline int pci_aer_clear_status(struct pci_dev *dev) { return -EINVAL; }
> >  static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL; }
> >  static inline void pci_save_aer_state(struct pci_dev *dev) { }
> >  static inline void pci_restore_aer_state(struct pci_dev *dev) { }
> > +static inline void pcie_do_recover_slots(struct pci_host_bridge *host)
> > +{
> > +	struct pci_bus *bus = host->bus;
> > +	struct pci_dev *dev;
> > +	int ret;
> > +
> > +	if (!host->reset_slot)
> > +		dev_warn(&host->dev, "Missing reset_slot() callback\n");
> > +
> > +	for_each_pci_bridge(dev, bus) {
> > +		if (!pci_is_root_bus(bus))
> > +			continue;
> > +
> > +		ret = pci_bus_error_reset(dev);
> > +		if (ret)
> > +			pci_err(dev, "Failed to reset slot: %d\n", ret);
> > +		else
> > +			pci_info(dev, "Slot has been reset\n");
> > +	}
> > +}
> >  #endif
> 
> Unusual to have such a large inline function in a header.
> Can this likewise be moved to some library file and separated
> from the other version via #ifdef please?
> 

Sure.

- Mani

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