linux-kernel - Re: [PATCH v7 1/2] phy: Add new Exynos5 USB 3.0 PHY driver

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Message-id: <536CA1B9.5070605@samsung.com>
Date:	Fri, 09 May 2014 11:36:57 +0200
From:	Tomasz Figa <t.figa@...sung.com>
To:	Mark Rutland <Mark.Rutland@....com>,
	Rob Herring <robh+dt@...nel.org>
Cc:	Vivek Gautam <gautam.vivek@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>, kishon <kishon@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-doc@...r.kernel.org,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Kamil Debski <k.debski@...sung.com>
Subject: Re: [PATCH v7 1/2] phy: Add new Exynos5 USB 3.0 PHY driver

[CCing DT maintainers]

On 08.05.2014 11:03, Vivek Gautam wrote:
> On Thu, May 8, 2014 at 11:35 AM, Vivek Gautam <gautam.vivek@...sung.com> wrote:
>> Hi Sylwester,
>>
>>
>> On Tue, May 6, 2014 at 7:57 PM, Sylwester Nawrocki
>> <s.nawrocki@...sung.com> wrote:
>>> On 28/04/14 08:17, Vivek Gautam wrote:
>>>> Add a new driver for the USB 3.0 PHY on Exynos5 series of SoCs.
>>>> The new driver uses the generic PHY framework and will interact
>>>> with DWC3 controller present on Exynos5 series of SoCs.
>>>> Thereby, removing old phy-samsung-usb3 driver and related code
>>>> used untill now which was based on usb/phy framework.
>>>>
>>>> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
>>>> ---
>>>>
>>>> Changes from v6:
>>>>  - Addressed review comments:
>>>>    -- Sorted config entries in Kconfig and Makefile
>>>>    -- Made #define to_usbdrd_phy(inst) to a static inline routine.
>>>>    -- Restructured exynos5_rate_to_clk() as suggested.
>>>>    -- Amended 'val' field for regmap_update_bits() in the routine
>>>>       exynos5_usbdrd_phy_isol().
>>>>    -- Removed sentinel entry from exynos5_usbdrd_phy_cfg[] struct.
>>>>    -- Removed check for 'match' entry in probe().
>>>>
>>>>  .../devicetree/bindings/phy/samsung-phy.txt        |   40 ++
>>>>  drivers/phy/Kconfig                                |   11 +
>>>>  drivers/phy/Makefile                               |    1 +
>>>>  drivers/phy/phy-exynos5-usbdrd.c                   |  627 ++++++++++++++++++++
>>>>  4 files changed, 679 insertions(+)
>>>>  create mode 100644 drivers/phy/phy-exynos5-usbdrd.c
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/phy/samsung-phy.txt b/Documentation/devicetree/bindings/phy/samsung-phy.txt
>>>> index b422e38..51efe4c 100644
>>>> --- a/Documentation/devicetree/bindings/phy/samsung-phy.txt
>>>> +++ b/Documentation/devicetree/bindings/phy/samsung-phy.txt
>>>> @@ -114,3 +114,43 @@ Example:
>>>>               compatible = "samsung,exynos-sataphy-i2c";
>>>>               reg = <0x38>;
>>>>       };
>>>> +
>>>> +Samsung Exynos5 SoC series USB DRD PHY controller
>>>> +--------------------------------------------------
>>>> +
>>>> +Required properties:
>>>> +- compatible : Should be set to one of the following supported values:
>>>> +     - "samsung,exynos5250-usbdrd-phy" - for exynos5250 SoC,
>>>> +     - "samsung,exynos5420-usbdrd-phy" - for exynos5420 SoC.
>>>> +- reg : Register offset and length of USB DRD PHY register set;
>>>> +- clocks: Clock IDs array as required by the controller
>>>> +- clock-names: names of clocks correseponding to IDs in the clock property;
>>>> +            Required clocks:
>>>> +     - phy: main PHY clock (same as USB DRD controller i.e. DWC3 IP clock),
>>>> +            used for register access.
>>>> +     - ref: PHY's reference clock (usually crystal clock), used for
>>>> +            PHY operations, associated by phy name. It is used to
>>>> +            determine bit values for clock settings register.
>>>> +            For Exynos5420 this is given as 'sclk_usbphy30' in CMU.
>>>> +- samsung,pmu-syscon: phandle for PMU system controller interface, used to
>>>> +                   control pmu registers for power isolation.
>>>> +- samsung,pmu-offset: phy power control register offset to pmu-system-controller
>>>> +                   base.
>>>
>>> It doesn't seem right to have register offset encoded in the device tree
>>> like this. I think it'd be more appropriate to associate such an offset
>>> with the compatible string's value in the driver.
>>
>> Ok, it makes more sense.
>> Just out of curiosity, what difference would this make ?
> 
> Moreover, in case of Exynos5420 (and may be in future SoCs), where we
> have 2 USB DRD PHY controllers,
> we will need to have a way around to deal with two separate offsets in
> the driver for one compatible string.
> 
> Getting the offsets from DT seems a cleaner way to handle this case of
> multi controllers.

Mark, Rob, what is your opinion on this?

Best regards,
Tomasz
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