linux-kernel - RE: [PATCH v4 3/9] phy: Add new Exynos USB PHY driver

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Date:	Wed, 18 Dec 2013 09:54:33 +0900
From:	Anton Tikhomirov <av.tikhomirov@...sung.com>
To:	'Kamil Debski' <k.debski@...sung.com>,
	linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	linux-usb@...r.kernel.org, devicetree@...r.kernel.org
Cc:	kyungmin.park@...sung.com, kishon@...com,
	'Tomasz Figa' <t.figa@...sung.com>,
	'Sylwester Nawrocki' <s.nawrocki@...sung.com>,
	'Marek Szyprowski' <m.szyprowski@...sung.com>,
	gautam.vivek@...sung.com, mat.krawczuk@...il.com,
	yulgon.kim@...sung.com, p.paneri@...sung.com, jg1.han@...sung.com,
	galak@...eaurora.org, matt.porter@...aro.org
Subject: RE: [PATCH v4 3/9] phy: Add new Exynos USB PHY driver

Hi Kamil,

> Hi Anton,
> 
> > From: Anton Tikhomirov [mailto:av.tikhomirov@...sung.com]
> > Sent: Tuesday, December 10, 2013 3:43 AM
> >
> > Hi Kamil,
> >
> > Same USB2.0 PHY may be used by several HCDs, for example EHCI and
> OHCI.
> > Consider the situation, when EHCI stops using the PHY and calls
> > power_off, then OHCI becomes non-operational. In other words, PHY
> > power_on and power_off calls must be balanced.
> >
> > Shall we handle it in your driver? (usage count?)
> 
> Please look in the drivers/phy/phy-core.c file. Usage count is handled
> there - see phy_power_on and phy_power_off functions. I understand that
> after both EHCI and OHCI power on the phy, the usage count is 2. So
> powering off one of them (EHCI for instance) the usage count is still
> 1, so the OHCI should still work properly.

Oops, sorry, missed that.

> 
> [snip]
> 
> Best wishes,
> --
> Kamil Debski
> Samsung R&D Institute Poland

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