Re: [PATCH 1/2] PCI/DPC: Add 'nodpc' parameter

["Derrick, Jonathan" <jonathan.derrick@intel.com>]

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On Thu, 2018-08-16 at 14:57 +0530, poza@codeaurora.org wrote:
> On 2018-08-16 02:56, Jon Derrick wrote:
> > Some users may want to disable downstream port containment (DPC),
> > so
> > give them this option
> > 
> > Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
> > ---
> >  drivers/pci/pci.c      |  2 ++
> >  drivers/pci/pci.h      |  6 ++++++
> >  drivers/pci/pcie/dpc.c | 48 
> > ++++++++++++++++++++++++++++++++++++++----------
> >  include/linux/pci.h    |  6 ++++++
> >  4 files changed, 52 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index 80da484..4e629c2 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -6062,6 +6062,8 @@ static int __init pci_setup(char *str)
> >  				pcie_ats_disabled = true;
> >  			} else if (!strcmp(str, "noaer")) {
> >  				pci_no_aer();
> > +			} else if (!strcmp(str, "nodpc")) {
> > +				pci_no_dpc();
> >  			} else if (!strcmp(str, "earlydump")) {
> >  				pci_early_dump = true;
> >  			} else if (!strncmp(str, "realloc=", 8)) {
> > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> > index 6e0d152..f73f29e 100644
> > --- a/drivers/pci/pci.h
> > +++ b/drivers/pci/pci.h
> > @@ -536,4 +536,10 @@ static inline void
> > pci_aer_clear_fatal_status(struct pci_dev *dev) { }
> >  static inline void pci_aer_clear_device_status(struct pci_dev
> > *dev) { 
> > }
> >  #endif
> > 
> > +#ifdef CONFIG_PCIE_DPC
> > +void pci_no_dpc(void);
> > +#else
> > +static inline void pci_no_dpc(void) { }
> > +#endif
> > +
> >  #endif /* DRIVERS_PCI_H */
> > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> > index f03279f..068fca0 100644
> > --- a/drivers/pci/pcie/dpc.c
> > +++ b/drivers/pci/pcie/dpc.c
> > @@ -44,6 +44,18 @@ struct dpc_dev {
> >  	"Memory Request Completion Timeout",		 /*
> > Bit Position 18 */
> >  };
> > 
> > +static int pcie_dpc_disable;
> > +
> > +void pci_no_dpc(void)
> > +{
> > +	pcie_dpc_disable = 1;
> > +}
> > +
> > +bool pci_dpc_available(void)
> > +{
> > +	return !pcie_dpc_disable && pci_aer_available() &&
> > pci_msi_enabled();
> 
> 1) why do you check pci_aer_available() ?
I'd assumed a dependency on aer, but looking at it again I see it calls
into err.c without a requirement on aer.

Then it also seems the pci_aer_available() and AER dependency check in
portdrv_core.c is unneccessary too.

> 2) and pci_aer_available() already internally checks
> pci_msi_enabled();
> 
> > +}
> > +
> >  static int dpc_wait_rp_inactive(struct dpc_dev *dpc)
> >  {
> >  	unsigned long timeout = jiffies + HZ;
> > @@ -209,6 +221,17 @@ static irqreturn_t dpc_irq(int irq, void
> > *context)
> >  	return IRQ_HANDLED;
> >  }
> > 
> > +static void dpc_disable(struct pci_dev *pdev)
> > +{
> > +	u16 cap_pos, ctl;
> > +
> > +	cap_pos = pci_find_ext_capability(pdev,
> > PCI_EXT_CAP_ID_DPC);
> > +	pci_read_config_word(pdev, cap_pos + PCI_EXP_DPC_CTL,
> > &ctl);
> > +	ctl &= ~(PCI_EXP_DPC_CTL_EN_FATAL |
> > PCI_EXP_DPC_CTL_EN_NONFATAL |
> > +		 PCI_EXP_DPC_CTL_INT_EN);
> > +	pci_write_config_word(pdev, cap_pos + PCI_EXP_DPC_CTL,
> > ctl);
> > +}
> > +
> >  #define FLAG(x, y) (((x) & (y)) ? '+' : '-')
> >  static int dpc_probe(struct pcie_device *dev)
> >  {
> > @@ -221,9 +244,16 @@ static int dpc_probe(struct pcie_device *dev)
> >  	if (pcie_aer_get_firmware_first(pdev))
> >  		return -ENOTSUPP;
> > 
> > +	if (!pci_dpc_available()) {
> > +		status = -ENOTSUPP;
> > +		goto disable_dpc;
> > +	}
> > +
> >  	dpc = devm_kzalloc(device, sizeof(*dpc), GFP_KERNEL);
> > -	if (!dpc)
> > -		return -ENOMEM;
> > +	if (!dpc) {
> > +		status = -ENOMEM;
> > +		goto disable_dpc;
> > +	}
> > 
> >  	dpc->cap_pos = pci_find_ext_capability(pdev,
> > PCI_EXT_CAP_ID_DPC);
> >  	dpc->dev = dev;
> > @@ -235,7 +265,7 @@ static int dpc_probe(struct pcie_device *dev)
> >  	if (status) {
> >  		dev_warn(device, "request IRQ%d failed: %d\n",
> > dev->irq,
> >  			 status);
> > -		return status;
> > +		goto disable_dpc;
> >  	}
> > 
> >  	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CAP,
> > &cap);
> > @@ -260,17 +290,15 @@ static int dpc_probe(struct pcie_device *dev)
> >  		FLAG(cap, PCI_EXP_DPC_CAP_SW_TRIGGER), dpc-
> > >rp_log_size,
> >  		FLAG(cap, PCI_EXP_DPC_CAP_DL_ACTIVE));
> >  	return status;
> > +
> > +disable_dpc:
> > +	dpc_disable(pdev);
> > +	return status;
> >  }
> > 
> >  static void dpc_remove(struct pcie_device *dev)
> >  {
> > -	struct dpc_dev *dpc = get_service_data(dev);
> > -	struct pci_dev *pdev = dev->port;
> > -	u16 ctl;
> > -
> > -	pci_read_config_word(pdev, dpc->cap_pos + PCI_EXP_DPC_CTL,
> > &ctl);
> > -	ctl &= ~(PCI_EXP_DPC_CTL_EN_FATAL |
> > PCI_EXP_DPC_CTL_INT_EN);
> > -	pci_write_config_word(pdev, dpc->cap_pos +
> > PCI_EXP_DPC_CTL, ctl);
> > +	dpc_disable(dev->port);
> >  }
> > 
> >  static struct pcie_port_service_driver dpcdriver = {
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 5454e6b..559b792 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1473,6 +1473,12 @@ static inline int pci_irqd_intx_xlate(struct
> > irq_domain *d,
> >  static inline bool pci_aer_available(void) { return false; }
> >  #endif
> > 
> > +#ifdef CONFIG_PCIE_DPC
> > +bool pci_dpc_available(void);
> > +#else
> > +static inline bool pci_dpc_available(void) { return false; }
> > +#endif
> > +
> >  #ifdef CONFIG_PCIE_ECRC
> >  void pcie_set_ecrc_checking(struct pci_dev *dev);
> >  void pcie_ecrc_get_policy(char *str);

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