[PATCH v1 3/4] PCI: brcmstb: Add control of subdevice voltage regulators
Jim Quinlan
james.quinlan at broadcom.com
Fri Jul 8 08:16:08 PDT 2022
On Wed, Jul 6, 2022 at 7:13 PM Bjorn Helgaas <helgaas at kernel.org> wrote:
>
> On Fri, Jul 01, 2022 at 12:27:24PM -0400, Jim Quinlan wrote:
> > This Broadcom STB PCIe RC driver has one port and connects directly to one
> > device, be it a switch or an endpoint. We want to be able to leverage the
> > recently added mechanism that allocates and turns on/off subdevice
> > regulators.
> >
> > All that needs to be done is to put the regulator DT nodes in the bridge
> > below host and to set the pci_ops methods add_bus and remove_bus.
> >
> > Note that the pci_subdev_regulators_add_bus() method is wrapped for two
> > reasons:
> >
> > 1. To achieve link up after the voltage regulators are turned on.
> >
> > 2. If, in the case of an unsuccessful link up, to redirect any PCIe
> > accesses to subdevices, e.g. the scan for DEV/ID. This redirection
> > is needed because the Broadcom PCIe HW will issue a CPU abort if such
> > an access is made when the link is down.
> >
> > [bhelgaas: fold in
> > https://lore.kernel.org/r/20220112013100.48029-1-jim2101024@gmail.com]
> > Link: https://lore.kernel.org/r/20220106160332.2143-7-jim2101024@gmail.com
> > Signed-off-by: Jim Quinlan <jim2101024 at gmail.com>
> > ---
> > drivers/pci/controller/pcie-brcmstb.c | 86 ++++++++++++++++++++++++---
> > 1 file changed, 77 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > index 661d3834c6da..a86bf502a265 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -196,6 +196,8 @@ static inline void brcm_pcie_bridge_sw_init_set_generic(struct brcm_pcie *pcie,
> > static inline void brcm_pcie_perst_set_4908(struct brcm_pcie *pcie, u32 val);
> > static inline void brcm_pcie_perst_set_7278(struct brcm_pcie *pcie, u32 val);
> > static inline void brcm_pcie_perst_set_generic(struct brcm_pcie *pcie, u32 val);
> > +static int brcm_pcie_linkup(struct brcm_pcie *pcie);
> > +static int brcm_pcie_add_bus(struct pci_bus *bus);
>
> I think the brcm_pcie_add_bus() declaration is unnecessary.
Will remove.
>
> The brcm_pcie_linkup() one is probably unnecessary, too, but would
> require a lot of reordering that I don't think we should do in this
> series.
I have a future commit that will remove all forward declarations. I just
wanted to keep this the un-revert patchset simple.
>
> > enum {
> > RGR1_SW_INIT_1,
> > @@ -329,6 +331,8 @@ struct brcm_pcie {
> > u32 hw_rev;
> > void (*perst_set)(struct brcm_pcie *pcie, u32 val);
> > void (*bridge_sw_init_set)(struct brcm_pcie *pcie, u32 val);
> > + bool refusal_mode;
> > + struct subdev_regulators *sr;
> > };
> >
> > static inline bool is_bmips(const struct brcm_pcie *pcie)
> > @@ -497,6 +501,33 @@ static int pci_subdev_regulators_add_bus(struct pci_bus *bus)
> > return 0;
> > }
> >
> > +static int brcm_pcie_add_bus(struct pci_bus *bus)
> > +{
> > + struct brcm_pcie *pcie = (struct brcm_pcie *) bus->sysdata;
> > + int ret;
> > +
> > + if (!bus->parent || !pci_is_root_bus(bus->parent))
> > + return 0;
> > +
> > + ret = pci_subdev_regulators_add_bus(bus);
> > + if (ret)
> > + return ret;
> > +
> > + /* Grab the regulators for suspend/resume */
> > + pcie->sr = bus->dev.driver_data;
> > +
> > + /*
> > + * If we have failed linkup there is no point to return an error as
> > + * currently it will cause a WARNING() from pci_alloc_child_bus().
> > + * We return 0 and turn on the "refusal_mode" so that any further
> > + * accesses to the pci_dev just get 0xffffffff
> > + */
> > + if (brcm_pcie_linkup(pcie) != 0)
> > + pcie->refusal_mode = true;
>
> Is there a bisection hole between the previous patch and this one?
> The previous patch sets .add_bus() to pci_subdev_regulators_add_bus(),
> so we'll turn on the regulators, but we don't know whether the link
> came up. If it didn't come up, it looks like we might get a CPU abort
> when enumerating?
I don't think so. At this commit, attempting the link-up is still
done before the call
to pci_host_probe(). Since there is no power there will be no link,
the probe will
fail and pci_host_probe() will never be invoked.
>
> I think we should split out the refusal_mode patch:
>
> - Add refusal mode
> - Add subdev regulator mechanism
> - This patch (which would then be clearly about managing regulators
> in suspend/resume, IIUC)
Will do.
>
> > + return 0;
> > +}
> > +
> > static void pci_subdev_regulators_remove_bus(struct pci_bus *bus)
> > {
> > struct device *dev = &bus->dev;
> > @@ -826,6 +857,18 @@ static void __iomem *brcm_pcie_map_conf(struct pci_bus *bus, unsigned int devfn,
> > /* Accesses to the RC go right to the RC registers if slot==0 */
> > if (pci_is_root_bus(bus))
> > return PCI_SLOT(devfn) ? NULL : base + where;
> > + if (pcie->refusal_mode) {
> > + /*
> > + * At this point we do not have link. There will be a CPU
> > + * abort -- a quirk with this controller --if Linux tries
> > + * to read any config-space registers besides those
> > + * targeting the host bridge. To prevent this we hijack
> > + * the address to point to a safe access that will return
> > + * 0xffffffff.
> > + */
> > + writel(0xffffffff, base + PCIE_MISC_RC_BAR2_CONFIG_HI);
> > + return base + PCIE_MISC_RC_BAR2_CONFIG_HI + (where & 0x3);
> > + }
> >
> > /* For devices, write to the config space index register */
> > idx = PCIE_ECAM_OFFSET(bus->number, devfn, 0);
> > @@ -854,7 +897,7 @@ static struct pci_ops brcm_pcie_ops = {
> > .map_bus = brcm_pcie_map_conf,
> > .read = pci_generic_config_read,
> > .write = pci_generic_config_write,
> > - .add_bus = pci_subdev_regulators_add_bus,
> > + .add_bus = brcm_pcie_add_bus,
> > .remove_bus = pci_subdev_regulators_remove_bus,
> > };
> >
> > @@ -1327,6 +1370,14 @@ static int brcm_pcie_suspend(struct device *dev)
> > return ret;
> > }
> >
> > + if (pcie->sr) {
> > + ret = regulator_bulk_disable(pcie->sr->num_supplies, pcie->sr->supplies);
> > + if (ret) {
> > + dev_err(dev, "Could not turn off regulators\n");
> > + reset_control_reset(pcie->rescal);
> > + return ret;
> > + }
> > + }
> > clk_disable_unprepare(pcie->clk);
> >
> > return 0;
> > @@ -1344,9 +1395,17 @@ static int brcm_pcie_resume(struct device *dev)
> > if (ret)
> > return ret;
> >
> > + if (pcie->sr) {
> > + ret = regulator_bulk_enable(pcie->sr->num_supplies, pcie->sr->supplies);
> > + if (ret) {
> > + dev_err(dev, "Could not turn on regulators\n");
> > + goto err_disable_clk;
> > + }
> > + }
> > +
> > ret = reset_control_reset(pcie->rescal);
> > if (ret)
> > - goto err_disable_clk;
> > + goto err_regulator;
> >
> > ret = brcm_phy_start(pcie);
> > if (ret)
> > @@ -1378,6 +1437,9 @@ static int brcm_pcie_resume(struct device *dev)
> >
> > err_reset:
> > reset_control_rearm(pcie->rescal);
> > +err_regulator:
> > + if (pcie->sr)
> > + regulator_bulk_disable(pcie->sr->num_supplies, pcie->sr->supplies);
> > err_disable_clk:
> > clk_disable_unprepare(pcie->clk);
> > return ret;
> > @@ -1488,10 +1550,6 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> > if (ret)
> > goto fail;
> >
> > - ret = brcm_pcie_linkup(pcie);
> > - if (ret)
> > - goto fail;
> > -
> > pcie->hw_rev = readl(pcie->base + PCIE_MISC_REVISION);
> > if (pcie->type == BCM4908 && pcie->hw_rev >= BRCM_PCIE_HW_REV_3_20) {
> > dev_err(pcie->dev, "hardware revision with unsupported PERST# setup\n");
> > @@ -1513,7 +1571,17 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> >
> > platform_set_drvdata(pdev, pcie);
> >
> > - return pci_host_probe(bridge);
> > + ret = pci_host_probe(bridge);
> > + if (!ret && !brcm_pcie_link_up(pcie))
> > + ret = -ENODEV;
> > +
> > + if (ret) {
> > + brcm_pcie_remove(pdev);
> > + return ret;
> > + }
> > +
> > + return 0;
> > +
> > fail:
> > __brcm_pcie_remove(pcie);
> > return ret;
> > @@ -1522,8 +1590,8 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> > MODULE_DEVICE_TABLE(of, brcm_pcie_match);
> >
> > static const struct dev_pm_ops brcm_pcie_pm_ops = {
> > - .suspend = brcm_pcie_suspend,
> > - .resume = brcm_pcie_resume,
> > + .suspend_noirq = brcm_pcie_suspend,
> > + .resume_noirq = brcm_pcie_resume,
>
> Can you name these brcm_pcie_suspend_noirq() and
> brcm_pcie_resume_noirq() to match the hook names?
Yes.
Jim Quintlan
Broadcom STB
>
> > };
> >
> > static struct platform_driver brcm_pcie_driver = {
> > --
> > 2.17.1
> >
> >
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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