Re: [PATCH 6/6] PCI: tegra: Add support to enable slot regulators

[Andrew Murray]

On Tue, Aug 27, 2019 at 09:54:17PM +0530, Vidya Sagar wrote:
> On 8/27/2019 9:17 PM, Andrew Murray wrote:
> > On Mon, Aug 26, 2019 at 01:01:43PM +0530, Vidya Sagar wrote:
> > > Add support to get regulator information of 3.3V and 12V supplies of a PCIe
> > > slot from the respective controller's device-tree node and enable those
> > > supplies. This is required in platforms like p2972-0000 where the supplies
> > > to x16 slot owned by C5 controller need to be enabled before attempting to
> > > enumerate the devices.
> > > 
> > > Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> > > ---
> > >   drivers/pci/controller/dwc/pcie-tegra194.c | 65 ++++++++++++++++++++++
> > >   1 file changed, 65 insertions(+)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> > > index 8a27b25893c9..97de2151a738 100644
> > > --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> > > +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> > > @@ -278,6 +278,8 @@ struct tegra_pcie_dw {
> > >   	u32 aspm_l0s_enter_lat;
> > >   	struct regulator *pex_ctl_supply;
> > > +	struct regulator *slot_ctl_3v3;
> > > +	struct regulator *slot_ctl_12v;
> > >   	unsigned int phy_count;
> > >   	struct phy **phys;
> > > @@ -1047,6 +1049,59 @@ static void tegra_pcie_downstream_dev_to_D0(struct tegra_pcie_dw *pcie)
> > >   	}
> > >   }
> > > +static void tegra_pcie_get_slot_regulators(struct tegra_pcie_dw *pcie)
> > > +{
> > > +	pcie->slot_ctl_3v3 = devm_regulator_get_optional(pcie->dev, "vpcie3v3");
> > > +	if (IS_ERR(pcie->slot_ctl_3v3))
> > > +		pcie->slot_ctl_3v3 = NULL;
> > > +
> > > +	pcie->slot_ctl_12v = devm_regulator_get_optional(pcie->dev, "vpcie12v");
> > > +	if (IS_ERR(pcie->slot_ctl_12v))
> > > +		pcie->slot_ctl_12v = NULL;
> > 
> > Do these need to take into consideration -EPROBE_DEFER?
> Since these are devm_* APIs, isn't it taken care of automatically?

devm_regulator_get_optional can still return -EPROBE_DEFER - for times when
"lookup could succeed in the future".

It's probably helpful here for your driver to distinguish between there not
being a regulator specified in the DT, and there being a regulator but there
is no device for it yet. For the latter case - your driver would probe but
nothing would enumerate.

See pcie-rockchip-host.c for an example of where this is handled.

Of course if, for whatever reason it is unlikely you'll ever get -EPROBE_DEFER
then maybe it's OK as it is.

Thanks,

Andrew Murray

> 
> > 
> > Thanks,
> > 
> > Andrew Murray
> > 
> > > +}
> > > +
> > > +static int tegra_pcie_enable_slot_regulators(struct tegra_pcie_dw *pcie)
> > > +{
> > > +	int ret;
> > > +
> > > +	if (pcie->slot_ctl_3v3) {
> > > +		ret = regulator_enable(pcie->slot_ctl_3v3);
> > > +		if (ret < 0) {
> > > +			dev_err(pcie->dev,
> > > +				"Failed to enable 3V3 slot supply: %d\n", ret);
> > > +			return ret;
> > > +		}
> > > +	}
> > > +
> > > +	if (pcie->slot_ctl_12v) {
> > > +		ret = regulator_enable(pcie->slot_ctl_12v);
> > > +		if (ret < 0) {
> > > +			dev_err(pcie->dev,
> > > +				"Failed to enable 12V slot supply: %d\n", ret);
> > > +			if (pcie->slot_ctl_3v3)
> > > +				regulator_disable(pcie->slot_ctl_3v3);
> > > +			return ret;
> > > +		}
> > > +	}
> > > +
> > > +	/*
> > > +	 * According to PCI Express Card Electromechanical Specification
> > > +	 * Revision 1.1, Table-2.4, T_PVPERL (Power stable to PERST# inactive)
> > > +	 * should be a minimum of 100ms.
> > > +	 */
> > > +	msleep(100);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static void tegra_pcie_disable_slot_regulators(struct tegra_pcie_dw *pcie)
> > > +{
> > > +	if (pcie->slot_ctl_12v)
> > > +		regulator_disable(pcie->slot_ctl_12v);
> > > +	if (pcie->slot_ctl_3v3)
> > > +		regulator_disable(pcie->slot_ctl_3v3);
> > > +}
> > > +
> > >   static int tegra_pcie_config_controller(struct tegra_pcie_dw *pcie,
> > >   					bool en_hw_hot_rst)
> > >   {
> > > @@ -1060,6 +1115,10 @@ static int tegra_pcie_config_controller(struct tegra_pcie_dw *pcie,
> > >   		return ret;
> > >   	}
> > > +	ret = tegra_pcie_enable_slot_regulators(pcie);
> > > +	if (ret < 0)
> > > +		goto fail_slot_reg_en;
> > > +
> > >   	ret = regulator_enable(pcie->pex_ctl_supply);
> > >   	if (ret < 0) {
> > >   		dev_err(pcie->dev, "Failed to enable regulator: %d\n", ret);
> > > @@ -1142,6 +1201,8 @@ static int tegra_pcie_config_controller(struct tegra_pcie_dw *pcie,
> > >   fail_core_clk:
> > >   	regulator_disable(pcie->pex_ctl_supply);
> > >   fail_reg_en:
> > > +	tegra_pcie_disable_slot_regulators(pcie);
> > > +fail_slot_reg_en:
> > >   	tegra_pcie_bpmp_set_ctrl_state(pcie, false);
> > >   	return ret;
> > > @@ -1174,6 +1235,8 @@ static int __deinit_controller(struct tegra_pcie_dw *pcie)
> > >   		return ret;
> > >   	}
> > > +	tegra_pcie_disable_slot_regulators(pcie);
> > > +
> > >   	ret = tegra_pcie_bpmp_set_ctrl_state(pcie, false);
> > >   	if (ret) {
> > >   		dev_err(pcie->dev, "Failed to disable controller %d: %d\n",
> > > @@ -1372,6 +1435,8 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
> > >   		return ret;
> > >   	}
> > > +	tegra_pcie_get_slot_regulators(pcie);
> > > +
> > >   	pcie->pex_ctl_supply = devm_regulator_get(dev, "vddio-pex-ctl");
> > >   	if (IS_ERR(pcie->pex_ctl_supply)) {
> > >   		dev_err(dev, "Failed to get regulator: %ld\n",
> > > -- 
> > > 2.17.1
> > > 
>