Re: [PATCH 4/5] PCI: cadence: Add Power Management ops for host and EP

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Mon, Jul 09, 2018 at 03:56:11PM +0000, Alan Douglas wrote:
> On 09 July 2018 16:34, Lorenzo Pieralisi wrote:
> > On Mon, Jun 25, 2018 at 09:30:52AM +0100, Alan Douglas wrote:
> > > These PM ops will enable/disable the optional PHYs if present.  The
> > > AXI link-down register in the host driver is now cleared in
> > > cdns_pci_map_bus since the link-down bit will be set if the PHY has
> > > been disabled.  It is not cleared when enabling the PHY, since the
> > > link will not yet be up.
> > 
> > It is not entirely clear what you mean here, can you elaborate please ?
> Thanks for taking a look at this.
> There is a "Link down indication bit" register in the cadence PCIe IP
> AXI Configuration  Registers, which will be set by the PCIe IP after
> each link- down occurrence.  This bit must be cleared before
> continuing, or accesses will hang.  When the PHY is disabled, the link
> will go down and this bit will be set by HW.  It will also be set
> after a secondary bus reset.
> 
> We cannot simply clear this bit when enabling the PHY, since at this
> stage the link may not come up (e.g. because the EP PHY is disabled),

I understand the approach and the reasoning, I still would like to
understand the use case that explains "because the EP PHY is disabled"
above and, related to the same question, why isn't this needed in
current driver version given that the host controller is probed out
of reset, I will apply the series then and update the commit log.

Lorenzo

> and so we need to clear it on the first access after link-up. In order
> to ensure this, I simply clear it on every config access, in
> cdns_pci_map_bus, I couldn't think of a good way to just do it once.
> 
> Regards,
> Alan
> > Thank you,
> > Lorenzo
> > 
> > > Signed-off-by: Alan Douglas <adouglas@cadence.com>
> > > ---
> > >  drivers/pci/controller/pcie-cadence-ep.c   |    1 +
> > >  drivers/pci/controller/pcie-cadence-host.c |    3 ++
> > >  drivers/pci/controller/pcie-cadence.c      |   30 ++++++++++++++++++++++++++++
> > >  drivers/pci/controller/pcie-cadence.h      |    4 +++
> > >  4 files changed, 38 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/pcie-cadence-ep.c b/drivers/pci/controller/pcie-cadence-ep.c
> > > index c02f33d..3eabd99 100644
> > > --- a/drivers/pci/controller/pcie-cadence-ep.c
> > > +++ b/drivers/pci/controller/pcie-cadence-ep.c
> > > @@ -555,6 +555,7 @@ static void cdns_pcie_ep_shutdown(struct platform_device *pdev)
> > >  	.driver = {
> > >  		.name = "cdns-pcie-ep",
> > >  		.of_match_table = cdns_pcie_ep_of_match,
> > > +		.pm	= &cdns_pcie_pm_ops,
> > >  	},
> > >  	.probe = cdns_pcie_ep_probe,
> > >  	.shutdown = cdns_pcie_ep_shutdown,
> > > diff --git a/drivers/pci/controller/pcie-cadence-host.c b/drivers/pci/controller/pcie-cadence-host.c
> > > index 36f3109..e3e9b7d 100644
> > > --- a/drivers/pci/controller/pcie-cadence-host.c
> > > +++ b/drivers/pci/controller/pcie-cadence-host.c
> > > @@ -61,6 +61,8 @@ struct cdns_pcie_rc {
> > >  	/* Check that the link is up */
> > >  	if (!(cdns_pcie_readl(pcie, CDNS_PCIE_LM_BASE) & 0x1))
> > >  		return NULL;
> > > +	/* Clear AXI link-down status */
> > > +	cdns_pcie_writel(pcie, CDNS_PCIE_AT_LINKDOWN, 0x0);
> > >
> > >  	/* Update Output registers for AXI region 0. */
> > >  	addr0 = CDNS_PCIE_AT_OB_REGION_PCI_ADDR0_NBITS(12) |
> > > @@ -345,6 +347,7 @@ static int cdns_pcie_host_probe(struct platform_device *pdev)
> > >  	.driver = {
> > >  		.name = "cdns-pcie-host",
> > >  		.of_match_table = cdns_pcie_host_of_match,
> > > +		.pm	= &cdns_pcie_pm_ops,
> > >  	},
> > >  	.probe = cdns_pcie_host_probe,
> > >  };
> > > diff --git a/drivers/pci/controller/pcie-cadence.c b/drivers/pci/controller/pcie-cadence.c
> > > index 2edc126..86f1b00 100644
> > > --- a/drivers/pci/controller/pcie-cadence.c
> > > +++ b/drivers/pci/controller/pcie-cadence.c
> > > @@ -217,3 +217,33 @@ int cdns_pcie_init_phy(struct device *dev, struct cdns_pcie *pcie)
> > >
> > >  	return ret;
> > >  }
> > > +
> > > +#ifdef CONFIG_PM_SLEEP
> > > +static int cdns_pcie_suspend_noirq(struct device *dev)
> > > +{
> > > +	struct cdns_pcie *pcie = dev_get_drvdata(dev);
> > > +
> > > +	cdns_pcie_disable_phy(pcie);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static int cdns_pcie_resume_noirq(struct device *dev)
> > > +{
> > > +	struct cdns_pcie *pcie = dev_get_drvdata(dev);
> > > +	int ret;
> > > +
> > > +	ret = cdns_pcie_enable_phy(pcie);
> > > +	if (ret) {
> > > +		dev_err(dev, "failed to enable phy\n");
> > > +		return ret;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +#endif
> > > +
> > > +const struct dev_pm_ops cdns_pcie_pm_ops = {
> > > +	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(cdns_pcie_suspend_noirq,
> > > +				      cdns_pcie_resume_noirq)
> > > +};
> > > diff --git a/drivers/pci/controller/pcie-cadence.h b/drivers/pci/controller/pcie-cadence.h
> > > index b342c80..ae6bf2a 100644
> > > --- a/drivers/pci/controller/pcie-cadence.h
> > > +++ b/drivers/pci/controller/pcie-cadence.h
> > > @@ -166,6 +166,9 @@
> > >  #define CDNS_PCIE_AT_IB_RP_BAR_ADDR1(bar) \
> > >  	(CDNS_PCIE_AT_BASE + 0x0804 + (bar) * 0x0008)
> > >
> > > +/* AXI link down register */
> > > +#define CDNS_PCIE_AT_LINKDOWN (CDNS_PCIE_AT_BASE + 0x0824)
> > > +
> > >  enum cdns_pcie_rp_bar {
> > >  	RP_BAR0,
> > >  	RP_BAR1,
> > > @@ -314,5 +317,6 @@ void cdns_pcie_set_outbound_region_for_normal_msg(struct cdns_pcie *pcie, u8 fn,
> > >  void cdns_pcie_disable_phy(struct cdns_pcie *pcie);
> > >  int cdns_pcie_enable_phy(struct cdns_pcie *pcie);
> > >  int cdns_pcie_init_phy(struct device *dev, struct cdns_pcie *pcie);
> > > +extern const struct dev_pm_ops cdns_pcie_pm_ops;
> > >
> > >  #endif /* _PCIE_CADENCE_H */
> > > --
> > > 1.7.1
> > >