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SubjectRe: [PATCH v1 3/4] PCI: brcmstb: Add control of subdevice voltage regulators
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@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.

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.

> 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 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)

> + 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?

> };
>
> static struct platform_driver brcm_pcie_driver = {
> --
> 2.17.1
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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