linux-kernel - Re: [PATCH V4 1/5] phy: Add new Exynos5 USB 3.0 PHY driver

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Date:	Mon, 14 Apr 2014 15:44:56 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Kishon Vijay Abraham I <kishon@...com>,
	Vivek Gautam <gautam.vivek@...sung.com>
CC:	Tomasz Figa <t.figa@...sung.com>,
	Linux USB Mailing List <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linux-doc@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
	Felipe Balbi <balbi@...com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Kamil Debski <k.debski@...sung.com>,
	Jingoo Han <jg1.han@...sung.com>,
	Sylwester Nawrocki <sylvester.nawrocki@...il.com>
Subject: Re: [PATCH V4 1/5] phy: Add new Exynos5 USB 3.0 PHY driver

On 14.04.2014 15:05, Kishon Vijay Abraham I wrote:
>
>
> On Monday 14 April 2014 05:35 PM, Vivek Gautam wrote:
>> Hi Kishon,
>>
>>
>> On Mon, Apr 14, 2014 at 5:24 PM, Kishon Vijay Abraham I <kishon@...com> wrote:
>>> Hi,
>>>
>>> On Wednesday 09 April 2014 04:36 PM, Tomasz Figa wrote:
>>>> Hi Vivek,
>>>>
>>>> Please see my comments inline.
>>>>
>>>> On 08.04.2014 16:36, 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>
>>>>> ---
>>>>>    .../devicetree/bindings/phy/samsung-phy.txt        |   42 ++
>>>>>    drivers/phy/Kconfig                                |   11 +
>>>>>    drivers/phy/Makefile                               |    1 +
>>>>>    drivers/phy/phy-exynos5-usbdrd.c                   |  668 ++++++++++++++++++++
>>>>>    4 files changed, 722 insertions(+)
>>>>>    create mode 100644 drivers/phy/phy-exynos5-usbdrd.c
>>>>
>>>> [snip]
>>>>
>>>>> +    Additional clock required for Exynos5420:
>>>>> +    - usb30_sclk_100m: Additional special clock used for PHY operation
>>>>> +               depicted as 'sclk_usbphy30' in CMU of Exynos5420.
>>>>
>>>> Are you sure this isn't simply a gate for the ref clock, as it can be found on
>>>> another SoC that is not upstream yet? I don't have documentation for Exynos
>>>> 5420 so I can't tell, but I'd like to ask you to recheck this.
>>>>
>>>>> +- samsung,syscon-phandle: phandle for syscon interface, which is used to
>>>>> +              control pmu registers for power isolation.
>>>>> +- samsung,pmu-offset: phy power control register offset to
>>>>> pmu-system-controller
>>>>> +              base.
>>>>> +- #phy-cells : from the generic PHY bindings, must be 1;
>>>>> +
>>>>> +For "samsung,exynos5250-usbdrd-phy" and "samsung,exynos5420-usbdrd-phy"
>>>>> +compatible PHYs, the second cell in the PHY specifier identifies the
>>>>> +PHY id, which is interpreted as follows:
>>>>> +  0 - UTMI+ type phy,
>>>>> +  1 - PIPE3 type phy,
>>>>> +
>>>>> +Example:
>>>>> +    usb3_phy: usbphy@...00000 {
>>>>> +        compatible = "samsung,exynos5250-usbdrd-phy";
>>>>> +        reg = <0x12100000 0x100>;
>>>>> +        clocks = <&clock 286>, <&clock 1>;
>>>>> +        clock-names = "phy", "usb3phy_refclk";
>>>>
>>>> Binding description above doesn't mention "usb3phy_refclk" entry.
>>>>
>>>>> +        samsung,syscon-phandle = <&pmu_syscon>;
>>>>> +        samsung,pmu-offset = <0x704>;
>>>>> +        #phy-cells = <1>;
>>>>> +    };
>>>>
>>>> [snip]
>>>>
>>>>> diff --git a/drivers/phy/phy-exynos5-usbdrd.c b/drivers/phy/phy-exynos5-usbdrd.c
>>>>> new file mode 100644
>>>>> index 0000000..ff54a7c
>>>>> --- /dev/null
>>>>> +++ b/drivers/phy/phy-exynos5-usbdrd.c
>>>>
>>>> [snip]
>>>>
>>>>> +static int exynos5_usbdrd_phy_probe(struct platform_device *pdev)
>>>>> +{
>>>>> +    struct device *dev = &pdev->dev;
>>>>> +    struct device_node *node = dev->of_node;
>>>>> +    struct exynos5_usbdrd_phy *phy_drd;
>>>>> +    struct phy_provider *phy_provider;
>>>>> +    struct resource *res;
>>>>> +    const struct of_device_id *match;
>>>>> +    const struct exynos5_usbdrd_phy_drvdata *drv_data;
>>>>> +    struct regmap *reg_pmu;
>>>>> +    u32 pmu_offset;
>>>>> +    int i;
>>>>> +
>>>>> +    /*
>>>>> +     * Exynos systems are completely DT enabled,
>>>>> +     * so lets not have any platform data support for this driver.
>>>>> +     */
>>>>> +    if (!node) {
>>>>> +        dev_err(dev, "no device node found\n");
>>>>
>>>> This error message is not very meaningful. I'd rather use something like "This
>>>> driver can be only instantiated using Device Tree".
>>>
>>> how about just adding depend_on OF in Kconfig?
>>
>> Already added a depend on 'OF'. Copying below the part of Kconfig in this patch.
>
> Alright.. Do we need the check then? If config_OF is enabled devices will be
> created using device tree no?

Not necessarily. Enabling support for OF doesn't mean that it is the 
only boot method that can be used. Legacy board files may be still 
available. I'm not sure why someone would try to instantiate this driver 
from them, though.

Best regards,
Tomasz
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