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Date: Sat, 27 Mar 2021 18:20:59 -0400
From: Jim Quinlan <jim2101024@...il.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-pci <linux-pci@...r.kernel.org>,
Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
Rob Herring <robh@...nel.org>, Mark Brown <broonie@...nel.org>,
bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
Jim Quinlan <james.quinlan@...adcom.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Florian Fainelli <f.fainelli@...il.com>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@...ts.infradead.org>,
"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE"
<linux-arm-kernel@...ts.infradead.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/6] PCI: brcmstb: Add control of EP voltage regulators
On Fri, Mar 26, 2021 at 4:11 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Fri, Mar 26, 2021 at 03:19:00PM -0400, Jim Quinlan wrote:
> > Control of EP regulators by the RC is needed because of the chicken-and-egg
>
> Can you expand "EP"? Not sure if this refers to "endpoint" or
> something else.
Yes I meant "endpoint" -- I will expand it.
>
> If this refers to a device in a slot, I guess it isn't necessarily aWe only support this feature for endpoint devices; it they hav
> PCIe *endpoint*; it could also be a switch upstream port.
True; to be precise I mean the device directly connected to the single RC port.
>
> > situation: although the regulator is "owned" by the EP and would be best
> > handled on its driver, the EP cannot be discovered and probed unless its
> > regulator is already turned on.
> >
> > Signed-off-by: Jim Quinlan <jim2101024@...il.com>
> > ---
> > drivers/pci/controller/pcie-brcmstb.c | 90 ++++++++++++++++++++++++++-
> > 1 file changed, 87 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > index e330e6811f0b..b76ec7d9af32 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -24,6 +24,7 @@
> > #include <linux/pci.h>
> > #include <linux/pci-ecam.h>
> > #include <linux/printk.h>
> > +#include <linux/regulator/consumer.h>
> > #include <linux/reset.h>
> > #include <linux/sizes.h>
> > #include <linux/slab.h>
> > @@ -169,6 +170,7 @@
> > #define SSC_STATUS_SSC_MASK 0x400
> > #define SSC_STATUS_PLL_LOCK_MASK 0x800
> > #define PCIE_BRCM_MAX_MEMC 3
> > +#define PCIE_BRCM_MAX_EP_REGULATORS 4
> >
> > #define IDX_ADDR(pcie) (pcie->reg_offsets[EXT_CFG_INDEX])
> > #define DATA_ADDR(pcie) (pcie->reg_offsets[EXT_CFG_DATA])
> > @@ -295,8 +297,27 @@ 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);
> > + struct regulator_bulk_data supplies[PCIE_BRCM_MAX_EP_REGULATORS];
> > + unsigned int num_supplies;
> > };
> >
> > +static int brcm_set_regulators(struct brcm_pcie *pcie, bool on)
> > +{
> > + struct device *dev = pcie->dev;
> > + int ret;
> > +
> > + if (!pcie->num_supplies)
> > + return 0;
> > + if (on)
> > + ret = regulator_bulk_enable(pcie->num_supplies, pcie->supplies);
> > + else
> > + ret = regulator_bulk_disable(pcie->num_supplies, pcie->supplies);
> > + if (ret)
> > + dev_err(dev, "failed to %s EP regulators\n",
> > + on ? "enable" : "disable");
> > + return ret;
> > +}
> > +
> > /*
> > * This is to convert the size of the inbound "BAR" region to the
> > * non-linear values of PCIE_X_MISC_RC_BAR[123]_CONFIG_LO.SIZE
> > @@ -1141,16 +1162,63 @@ static void brcm_pcie_turn_off(struct brcm_pcie *pcie)
> > pcie->bridge_sw_init_set(pcie, 1);
> > }
> >
> > +static int brcm_pcie_get_regulators(struct brcm_pcie *pcie)
> > +{
> > + struct device_node *child, *parent = pcie->np;
> > + const unsigned int max_name_len = 64 + 4;
> > + struct property *pp;
> > +
> > + /* Look for regulator supply property in the EP device subnodes */
> > + for_each_available_child_of_node(parent, child) {
> > + /*
> > + * Do a santiy test to ensure that this is an EP node
>
> s/santiy/sanity/
>
> > + * (e.g. node name: "pci-ep@0,0"). The slot number
> > + * should always be 0 as our controller only has a single
> > + * port.
> > + */
> > + const char *p = strstr(child->full_name, "@0");
> > +
> > + if (!p || (p[2] && p[2] != ','))
> > + continue;
> > +
> > + /* Now look for regulator supply properties */
> > + for_each_property_of_node(child, pp) {
> > + int i, n = strnlen(pp->name, max_name_len);
> > +
> > + if (n <= 7 || strncmp("-supply", &pp->name[n - 7], 7))
> > + continue;
> > +
> > + /* Make sure this is not a duplicate */
> > + for (i = 0; i < pcie->num_supplies; i++)
> > + if (strncmp(pcie->supplies[i].supply,
> > + pp->name, max_name_len) == 0)
> > + continue;
> > +
> > + if (pcie->num_supplies < PCIE_BRCM_MAX_EP_REGULATORS)
> > + pcie->supplies[pcie->num_supplies++].supply = pp->name;
> > + else
> > + dev_warn(pcie->dev, "No room for EP supply %s\n",
> > + pp->name);
> > + }
> > + }
> > + /*
> > + * Get the regulators that the EP devices require. We cannot use
> > + * pcie->dev as the device argument in regulator_bulk_get() since
> > + * it will not find the regulators. Instead, use NULL and the
> > + * regulators are looked up by their name.
>
> The comment doesn't explain the interesting part of why you need NULL
> instead of "pcie->dev". I assume it has something to do with the
> platform topology and its DT description.
>
> This appears to be the only instance in the whole kernel of a use of
> regulator_bulk_get() or devm_regulator_bulk_get() with NULL. That
> definitely warrants a comment, so I'm glad you've got something here.
>
> The regulator_bulk_get() function comment doesn't mention the
> possibility of "dev == NULL", although regulator_dev_lookup(),
> create_regulator(), device_link_add() do check for it being NULL, so I
> guess it's not a surprise. We may call dev_err(NULL), which I thinkWe only support this feature for endpoint devices; it they hav
> will *work* without crashing even though it will look like a mistake
> on the output.
Folks wanted me to put the "supply" in the endpoint subnode. After
looking at the regulator code I assumed that using the pcie->dev in
this call would not work as the supply property is not in its DT node.
Turns out it works fine; I will fix it.
>
> > + */
> > + return regulator_bulk_get(NULL, pcie->num_supplies, pcie->supplies);
>
> devm_regulator_bulk_get()?
Yep.
>
> > +}
> > +
> > static int brcm_pcie_suspend(struct device *dev)
> > {
> > struct brcm_pcie *pcie = dev_get_drvdata(dev);
> > - int ret;
> >
> > brcm_pcie_turn_off(pcie);
> > - ret = brcm_phy_stop(pcie);
> > + brcm_phy_stop(pcie);We only support this feature for endpoint devices; it they hav
>
> If we no longer care whether brcm_phy_stop() returns an error, nobody
> looks at the return value and it could be void.
Will fix.
Thanks,
Jim Quinlan
Broadcom STB
>
> > clk_disable_unprepare(pcie->clk);
> >
> > - return ret;
> > + return brcm_set_regulators(pcie, false);
> > }
> >
> > static int brcm_pcie_resume(struct device *dev)
> > @@ -1163,6 +1231,10 @@ static int brcm_pcie_resume(struct device *dev)
> > base = pcie->base;
> > clk_prepare_enable(pcie->clk);
> >
> > + ret = brcm_set_regulators(pcie, true);
> > + if (ret)
> > + return ret;
> > +
> > ret = brcm_phy_start(pcie);
> > if (ret)
> > goto err;
> > @@ -1199,6 +1271,8 @@ static void __brcm_pcie_remove(struct brcm_pcie *pcie)
> > brcm_phy_stop(pcie);
> > reset_control_assert(pcie->rescal);
> > clk_disable_unprepare(pcie->clk);
> > + brcm_set_regulators(pcie, false);
> > + regulator_bulk_free(pcie->num_supplies, pcie->supplies);
> > }
> >
> > static int brcm_pcie_remove(struct platform_device *pdev)
> > @@ -1289,6 +1363,16 @@ static int brcm_pcie_probe(struct platform_device *pdev)
> > return ret;
> > }
> >
> > + ret = brcm_pcie_get_regulators(pcie);
> > + if (ret) {
> > + dev_err(pcie->dev, "failed to get regulators (err=%d)\n", ret);
> > + goto fail;
> > + }
> > +
> > + ret = brcm_set_regulators(pcie, true);
> > + if (ret)
> > + goto fail;
> > +
> > ret = brcm_pcie_setup(pcie);
> > if (ret)
> > goto fail;
> > --
> > 2.17.1
> >
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