linux-kernel - Re: [PATCH v2] usb: host: ehci-platform: add support for optional external vbus supply

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Date:   Tue, 20 Feb 2018 14:46:07 +0000
From:   Amelie DELAUNAY <amelie.delaunay@...com>
To:     Roger Quadros <rogerq@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Tony Prisk <linux@...sktech.co.nz>,
        Alan Stern <stern@...land.harvard.edu>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] usb: host: ehci-platform: add support for optional
 external vbus supply

Hi,

On 02/20/2018 03:00 PM, Roger Quadros wrote:
> Hi,
> 
> On 20/02/18 14:58, Amelie Delaunay wrote:
>> On some boards, especially when vbus supply requires large current,
>> and the charge pump on the PHY isn't enough, an external vbus power switch
>> may be used.
>> Add support for this optional external vbus supply in ehci-platform.
>>
>> Signed-off-by: Amelie Delaunay <amelie.delaunay@...com>
>>
>> ---
>> Changes in v2:
>>   * Address Roger Quadros comments: move regulator_enable/disable from
>> ehci_platform_power_on/off to ehci_platform_port_power.
>> ---
>>   Documentation/devicetree/bindings/usb/usb-ehci.txt |  1 +
>>   drivers/usb/host/ehci-platform.c                   | 31 ++++++++++++++++++++++
>>   2 files changed, 32 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/usb/usb-ehci.txt b/Documentation/devicetree/bindings/usb/usb-ehci.txt
>> index 3efde12..fc480cd 100644
>> --- a/Documentation/devicetree/bindings/usb/usb-ehci.txt
>> +++ b/Documentation/devicetree/bindings/usb/usb-ehci.txt
>> @@ -19,6 +19,7 @@ Optional properties:
>>    - phys : phandle + phy specifier pair
>>    - phy-names : "usb"
>>    - resets : phandle + reset specifier pair
>> + - vbus-supply : phandle of regulator supplying vbus
>>   
> 
> Can platforms have more than one regulator e.g. one regulator per port?
> 

I imagine that yes, platforms could have one regulator per port.
Regulator consumers bindings impose a <name>-supply property per 
regulator, so, what do you think about :
vbus0-supply for port#0
vbus1-supply for port#1
...
vbusN-supply for port#N

And then in probe, allocate 'struct regulator *vbus_supplies' with a 
size corresponding to 'HCS_N_PORTS(ehci->hcs_params) * sizeof(struct 
regulator *)'.
And loop to get optional regulator vbus0, vbus1,..., vbusN.
And then enable/disable the corresponding regulator in 
ehci_platform_port_power thanks to portnum.

>>   Example (Sequoia 440EPx):
>>       ehci@...00300 {
>> diff --git a/drivers/usb/host/ehci-platform.c b/drivers/usb/host/ehci-platform.c
>> index b065a96..05be100 100644
>> --- a/drivers/usb/host/ehci-platform.c
>> +++ b/drivers/usb/host/ehci-platform.c
>> @@ -29,6 +29,7 @@
>>   #include <linux/of.h>
>>   #include <linux/phy/phy.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/regulator/consumer.h>
>>   #include <linux/reset.h>
>>   #include <linux/usb.h>
>>   #include <linux/usb/hcd.h>
>> @@ -46,6 +47,7 @@ struct ehci_platform_priv {
>>   	struct reset_control *rsts;
>>   	struct phy **phys;
>>   	int num_phys;
>> +	struct regulator *vbus_supply;
>>   	bool reset_on_resume;
>>   };
>>   
>> @@ -76,6 +78,25 @@ static int ehci_platform_reset(struct usb_hcd *hcd)
>>   	return 0;
>>   }
>>   
>> +static int ehci_platform_port_power(struct usb_hcd *hcd, int portnum,
>> +				    bool enable)
>> +{
>> +	struct ehci_platform_priv *priv = hcd_to_ehci_priv(hcd);
>> +	int ret = 0;
>> +
>> +	if (priv->vbus_supply) {
>> +		if (enable)
>> +			ret = regulator_enable(priv->vbus_supply);
>> +		else
>> +			ret = regulator_disable(priv->vbus_supply);
>> +		if (ret)
>> +			dev_err(hcd->self.controller,
>> +				"failed to %s vbus supply: %d\n",
>> +				enable ? "enable" : "disable", ret);
>> +	}
>> +	return ret;
>> +}
>> +
>>   static int ehci_platform_power_on(struct platform_device *dev)
>>   {
>>   	struct usb_hcd *hcd = platform_get_drvdata(dev);
>> @@ -134,6 +155,7 @@ static struct hc_driver __read_mostly ehci_platform_hc_driver;
>>   static const struct ehci_driver_overrides platform_overrides __initconst = {
>>   	.reset =		ehci_platform_reset,
>>   	.extra_priv_size =	sizeof(struct ehci_platform_priv),
>> +	.port_power =		ehci_platform_port_power,
>>   };
>>   
>>   static struct usb_ehci_pdata ehci_platform_defaults = {
>> @@ -247,6 +269,15 @@ static int ehci_platform_probe(struct platform_device *dev)
>>   	if (err)
>>   		goto err_put_clks;
>>   
>> +	priv->vbus_supply = devm_regulator_get_optional(&dev->dev, "vbus");
>> +	if (IS_ERR(priv->vbus_supply)) {
>> +		err = PTR_ERR(priv->vbus_supply);
>> +		if (err == -ENODEV)
>> +			priv->vbus_supply = NULL;
>> +		else
>> +			goto err_reset;
>> +	}
>> +
>>   	if (pdata->big_endian_desc)
>>   		ehci->big_endian_desc = 1;
>>   	if (pdata->big_endian_mmio)
>>
>