linux-kernel - Re: [PATCH 1/3] usb: ohci-exynos: Make provision for vdd regulators

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Message-ID: <CAFp+6iFTVKHcF8zyfmFcrALHDaRHwXOC3Wbd7rv_X5LvjznPgg@mail.gmail.com>
Date:	Thu, 24 Apr 2014 12:02:57 +0530
From:	Vivek Gautam <gautam.vivek@...sung.com>
To:	Anton Tikhomirov <av.tikhomirov@...sung.com>
Cc:	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-omap@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Felipe Balbi <balbi@...com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Jingoo Han <jg1.han@...sung.com>
Subject: Re: [PATCH 1/3] usb: ohci-exynos: Make provision for vdd regulators

Hi,


On Thu, Apr 24, 2014 at 6:08 AM, Anton Tikhomirov
<av.tikhomirov@...sung.com> wrote:
> Hi,
>
>> Hi,
>>
>> > -----Original Message-----
>> > From: linux-usb-owner@...r.kernel.org [mailto:linux-usb-
>> > owner@...r.kernel.org] On Behalf Of Vivek Gautam
>> > Sent: Monday, April 21, 2014 9:17 PM
>> >
>> > Facilitate getting required 3.3V and 1.0V VDD supply for
>> > OHCI controller on Exynos.
>> >
>> > With patches for regulators' nodes merged in 3.15:
>> > c8c253f ARM: dts: Add regulator entries to smdk5420
>> > 275dcd2 ARM: dts: add max77686 pmic node for smdk5250,
>> >
>> > certain perripherals will now need to ensure that,
>> > they request VDD regulators in their drivers, and enable
>> > them so as to make them working.
>> >
>> > Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
>> > Cc: Jingoo Han <jg1.han@...sung.com>
>> > ---
>> >
>> > Based on 'usb-next' branch of Greg's usb tree.
>> >
>> >  drivers/usb/host/ohci-exynos.c |   47
>> > ++++++++++++++++++++++++++++++++++++++++
>> >  1 file changed, 47 insertions(+)
>> >
>> > diff --git a/drivers/usb/host/ohci-exynos.c b/drivers/usb/host/ohci-
>> > exynos.c
>> > index 68588d8..e2e72a8 100644
>> > --- a/drivers/usb/host/ohci-exynos.c
>> > +++ b/drivers/usb/host/ohci-exynos.c

[snip]

>> >  static void exynos_ohci_phy_enable(struct platform_device *pdev)
>> > @@ -98,6 +101,28 @@ static int exynos_ohci_probe(struct
>> platform_device
>> > *pdev)
>> >             exynos_ohci->otg = phy->otg;
>> >     }
>> >
>> > +   exynos_ohci->vdd33 = devm_regulator_get(&pdev->dev, "vdd33");
>> > +   if (IS_ERR(exynos_ohci->vdd33)) {
>> > +           err = PTR_ERR(exynos_ohci->vdd33);
>> > +           goto fail_regulator1;
>> > +   }
>> > +   err = regulator_enable(exynos_ohci->vdd33);
>> > +   if (err) {
>> > +           dev_err(&pdev->dev, "Failed to enable VDD33 supply\n");
>> > +           goto fail_regulator1;
>> > +   }
>> > +
>> > +   exynos_ohci->vdd10 = devm_regulator_get(&pdev->dev, "vdd10");
>> > +   if (IS_ERR(exynos_ohci->vdd10)) {
>> > +           err = PTR_ERR(exynos_ohci->vdd10);
>> > +           goto fail_regulator2;
>> > +   }
>> > +   err = regulator_enable(exynos_ohci->vdd10);
>> > +   if (err) {
>> > +           dev_err(&pdev->dev, "Failed to enable VDD10 supply\n");
>> > +           goto fail_regulator2;
>> > +   }
>> > +
>>
>> Do we need to skip regulator settings together with PHY configuration
>> in case of exynos5440?
>>
>> >  skip_phy:
>> >     exynos_ohci->clk = devm_clk_get(&pdev->dev, "usbhost");
>> >

[snip]

>> > @@ -218,6 +253,18 @@ static int exynos_ohci_resume(struct device *dev)
>> >     struct usb_hcd *hcd                     = dev_get_drvdata(dev);
>> >     struct exynos_ohci_hcd *exynos_ohci     = to_exynos_ohci(hcd);
>> >     struct platform_device *pdev            = to_platform_device(dev);
>> > +   int ret;
>> > +
>> > +   ret = regulator_enable(exynos_ohci->vdd33);
>> > +   if (ret) {
>> > +           dev_err(dev, "Failed to enable VDD33 supply\n");
>> > +           return ret;
>>
>> Not sure, but shall we continue resuming and do everything
>> we can in case of error? At least it will avoid
>> WARN_ON(clk->enable_count == 0) on next system suspend.

True, i will modify it.
>
> On the other hand, if power is not applied to the controller,
> register access in ohci_resume() may lead to undefined behavior.
> What's your opinion?

AFA i think, it is obvious that the regulators would not work without
a VDD supply.
So the question is, do we have VDD LDOs available on all Exynos
systems for usb ?
>From the schemata of Exynos5250 and Exynos5420 boards, i can see the
required VDD LDOs
for USB. Unfortunately at present i don't have a Exynos4* schemata.

If regulator is not a mandatory, then we can make it option similar to
what Jingoo has also suggested
in subsequent mail.

[snip]


-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
--
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