Subject: [PATCHv5 10/20] phy: add support for USB cluster on the Armada 375 SoC

From: [email-masked] (Gregory CLEMENT)
Date: Thu, 15 May 2014 11:35:29 +0200

Hi Kishon,

On 15/05/2014 11:01, Kishon Vijay Abraham I wrote:
> Hi,
> 
> On Thursday 15 May 2014 12:31 PM, Gregory CLEMENT wrote:
>> Hi Kishon,
>>
>> On 14/05/2014 17:35, Gregory CLEMENT wrote:
>>> On 14/05/2014 16:27, Kishon Vijay Abraham I wrote:
>>>> Hi,
>>>>
>>>> On Tuesday 13 May 2014 03:11 PM, Gregory CLEMENT wrote:
>>>>> On 13/05/2014 10:06, Gregory CLEMENT wrote:
>>>>>> On 13/05/2014 07:53, Kishon Vijay Abraham I wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> On Sunday 11 May 2014 11:47 PM, Thomas Petazzoni wrote:
>>>>>>>> From: Gregory CLEMENT <[email-masked]>
>>>>>>>>
>>>>>>>> The Armada 375 SoC comes with an USB2 host and device controller and
>>>>>>>> an USB3 controller. The USB cluster control register allows to manage
>>>>>>>> common features of both USB controllers.
>>>>>>>>
>>>>>>>> This commit adds a driver integrated in the generic PHY framework to
>>>>>>>> control this USB cluster feature.
>>>>>>>>
>>>>>>>> Signed-off-by: Gregory CLEMENT <[email-masked]>
>>>>>>>> Signed-off-by: Thomas Petazzoni <[email-masked]>
>>>>>>>> ---
>>>>>>>>  drivers/phy/Kconfig              |   6 ++
>>>>>>>>  drivers/phy/Makefile             |   1 +
>>>>>>>>  drivers/phy/phy-armada375-usb2.c | 157 +++++++++++++++++++++++++++++++++++++++
>>>>>>>>  3 files changed, 164 insertions(+)
>>>>>>>>  create mode 100644 drivers/phy/phy-armada375-usb2.c
>>>>>>>>
>>>>>>>> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
>>>>>>>> index 3bb05f1..e63cf9d 100644
>>>>>>>> --- a/drivers/phy/Kconfig
>>>>>>>> +++ b/drivers/phy/Kconfig
>>>>>>>> @@ -15,6 +15,12 @@ config GENERIC_PHY
>>>>>>>>  	  phy users can obtain reference to the PHY. All the users of this
>>>>>>>>  	  framework should select this config.
>>>>>>>>  
>>>>>>>> +config ARMADA375_USBCLUSTER_PHY
>>>>>>>> +	def_bool y
>>>>>>>> +	depends on MACH_ARMADA_375 || COMPILE_TEST
>>>>>>>> +	depends on OF
>>>>>>>> +	select GENERIC_PHY
>>>>>>>> +
>>>>>>>>  config PHY_EXYNOS_MIPI_VIDEO
>>>>>>>>  	tristate "S5P/EXYNOS SoC series MIPI CSI-2/DSI PHY driver"
>>>>>>>>  	depends on HAS_IOMEM
>>>>>>>> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
>>>>>>>> index 2faf78e..47d5a86 100644
>>>>>>>> --- a/drivers/phy/Makefile
>>>>>>>> +++ b/drivers/phy/Makefile
>>>>>>>> @@ -3,6 +3,7 @@
>>>>>>>>  #
>>>>>>>>  
>>>>>>>>  obj-$(CONFIG_GENERIC_PHY)		+= phy-core.o
>>>>>>>> +obj-$(CONFIG_ARMADA375_USBCLUSTER_PHY)	+= phy-armada375-usb2.o
>>>>>>>>  obj-$(CONFIG_BCM_KONA_USB2_PHY)		+= phy-bcm-kona-usb2.o
>>>>>>>>  obj-$(CONFIG_PHY_EXYNOS_DP_VIDEO)	+= phy-exynos-dp-video.o
>>>>>>>>  obj-$(CONFIG_PHY_EXYNOS_MIPI_VIDEO)	+= phy-exynos-mipi-video.o
>>>>>>>> diff --git a/drivers/phy/phy-armada375-usb2.c b/drivers/phy/phy-armada375-usb2.c
>>>>>>>> new file mode 100644
>>>>>>>> index 0000000..a6f746d
>>>>>>>> --- /dev/null
>>>>>>>> +++ b/drivers/phy/phy-armada375-usb2.c
>>>>>>>> @@ -0,0 +1,157 @@
>>>>>>>> +/*
>>>>>>>> + * USB cluster support for Armada 375 platform.
>>>>>>>> + *
>>>>>>>> + * Copyright (C) 2014 Marvell
>>>>>>>> + *
>>>>>>>> + * Gregory CLEMENT <[email-masked]>
>>>>>>>> + *
>>>>>>>> + * This file is licensed under the terms of the GNU General Public
>>>>>>>> + * License version 2 or later. This program is licensed "as is"
>>>>>>>> + * without any warranty of any kind, whether express or implied.
>>>>>>>> + *
>>>>>>>> + * Armada 375 comes with an USB2 host and device controller and an
>>>>>>>> + * USB3 controller. The USB cluster control register allows to manage
>>>>>>>> + * common features of both USB controllers.
>>>>>>>> + */
>>>>>>>> +
>>>>>>>> +#include <linux/init.h>
>>>>>>>> +#include <linux/io.h>
>>>>>>>> +#include <linux/kernel.h>
>>>>>>>> +#include <linux/module.h>
>>>>>>>> +#include <linux/of_address.h>
>>>>>>>> +#include <linux/phy/phy.h>
>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>> +#include <linux/slab.h>
>>>>>>>> +
>>>>>>>> +#define USB2_PHY_CONFIG_DISABLE BIT(0)
>>>>>>>> +
>>>>>>>> +/* The USB cluster allows to choose between two PHYs */
>>>>>>>> +#define NB_PHY 2
>>>>>>>> +
>>>>>>>> +enum {
>>>>>>>> +	PHY_USB2 = 0,
>>>>>>>> +	PHY_USB3 = 1,
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +struct armada375_cluster_phy {
>>>>>>>> +	struct phy *phy;
>>>>>>>> +	void __iomem *reg;
>>>>>>>> +	bool enable;
>>>>>>>> +	bool use_usb3;
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +struct armada375_cluster_phy usb_cluster_phy[NB_PHY];
>>>>>>>> +
>>>>>>>> +static int armada375_usb_phy_init(struct phy *phy)
>>>>>>>> +{
>>>>>>>> +	struct armada375_cluster_phy *cluster_phy = phy_get_drvdata(phy);
>>>>>>>> +	u32 reg;
>>>>>>>
>>>>>>> This function should be protected since both your PHYs use this ops.
>>>>>>
>>>>>> Right
>>>>>
>>>>> Actually only one PHY can access this register. See the probe function,
>>>>> cluster_phy->enable is only set to true for one PHY.
>>>>>
>>>>>>
>>>>>>>> +
>>>>>>>> +	if (!cluster_phy->enable)
>>>>>>>> +		return -ENODEV;
>>>>>>>> +
>>>>>>>> +	reg = readl(cluster_phy->reg);
>>>>>>>> +	if (cluster_phy->use_usb3)
>>>>>>>> +		reg |= USB2_PHY_CONFIG_DISABLE;
>>>>>>>> +	else
>>>>>>>> +		reg &= ~USB2_PHY_CONFIG_DISABLE;
>>>>>>>> +	writel(reg, cluster_phy->reg);
>>>>>>>
>>>>>>> This is confusing since both your PHYs control the same bit?
>>>>>
>>>>> Same here at the end the bit is accessed by only one PHY.
>>>>>
>>>>>>>> +
>>>>>>>> +	return 0;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static struct phy_ops armada375_usb_phy_ops = {
>>>>>>>> +	.init = armada375_usb_phy_init,
>>>>>>>> +	.owner		= THIS_MODULE,
>>>>>>>> +};
>>>>>>>> +
>>>>>>>> +static struct phy *armada375_usb_phy_xlate(struct device *dev,
>>>>>>>> +					struct of_phandle_args *args)
>>>>>>>> +{
>>>>>>>> +	if (WARN_ON(args->args[0] >= NB_PHY))
>>>>>>>> +		return ERR_PTR(-ENODEV);
>>>>>>>> +
>>>>>>>> +	return usb_cluster_phy[args->args[0]].phy;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>> +static int armada375_usb_phy_probe(struct platform_device *pdev)
>>>>>>>> +{
>>>>>>>> +	struct device *dev = &pdev->dev;
>>>>>>>> +	struct phy *phy;
>>>>>>>> +	struct phy_provider *phy_provider;
>>>>>>>> +	void __iomem *usb_cluster_base;
>>>>>>>> +	struct device_node *xhci_node;
>>>>>>>> +	struct resource *res;
>>>>>>>> +	int i;
>>>>>>>> +
>>>>>>>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>>>>>> +	usb_cluster_base = devm_ioremap_resource(&pdev->dev, res);
>>>>>>>> +	if (!usb_cluster_base)
>>>>>>>> +		return -ENOMEM;
>>>>>>>> +
>>>>>>>> +	for (i = 0; i < NB_PHY; i++) {
>>>>>>>
>>>>>>> For devices which have multiple PHYs, each PHY should be modelled as the
>>>>>>> sub-node of the *PHY provider* device node.
>>>>>>
>>>>>> Actually it is the opposite the same PHY is shared between the EHCI
>>>>>> and the xHCI controllers. It is more a PHY muxer than a PHY itself.
>>>>>>
>>>>>> I had to create 2 logical PHYs because once the phy_init() is called
>>>>>> by a USB driver then the .init ops is not called anymore by the next
>>>>>> call to phy_init(). One of the goal of this is to disable a port for
>>>>>> the USB controller which can't use it due to the configuration of the
>>>>>> USB cluster.
>>>>>>
>>>>>> But I can see how to make this two "pseudo" PHYs sub-node of the *PHY
>>>>>> provider* device node. It shouldn't change the internal logic of this
>>>>>> driver.
>>>>>
>>>>> I need to make a distinction when the PHY access by the xHCI or when
>>>>> it was access by the EHCI. If I create two new sub-node then I will
>>>>> also need to add a property to make this distinction. It seems a little
>>>>> overkill for the need.
>>>>
>>>> Alright, so you have a single PHY that can be used by either XHCI or EHCI? And
>>>> the use of PHY is mutually exclusive? How should it behave if you have both
>>>> XHCI and EHCI?
>>>
>>> if we have both XHCI and EHCI then it is the USB2_PHY_CONFIG_DISABLE which
>>> determine which one is used. By default we decide to select the XHCI.
>>>
>>>>
>>>> One way to configure the PHY to a particular mode is by passing it as phandle
>>>> arguments. I think you can use that to enable or disable USB2_PHY_CONFIG_DISABLE?
>>>
>>> actually it was more or less what I do:
>>> for the XHCI I use:
>>> phys = <&usbcluster 1>;
>>> which enable the USB2_PHY_CONFIG_DISABLE
>>>
>>> for the EHCI I use phys = <&usbcluster 0>;
>>> which disable the USB2_PHY_CONFIG_DISABLE
>>>
>>> If I had to create two PHY it was because of the behavior of
>>> phy_init(). I need to be able to disable a controller if it can't use
>>> the PHY. For this purpose my ops->init() exits in error. However
>>> phy_init() will call ops->init() only one time, then the internal
>>> counter init_count will be incremented, and the next call to phy_init
>>> will skip the call to ops->init. And the behavior is the same for
>>> phy_power_on().
>>>
>>> So given this I don't see how to do in an other way except by
>>> modifying the value of the counter in my ops.
>>
>> What do you prefer here? Keep the current implementation or using
>> only one PHY by passing a argument through the phandle and in the
>> same time hacking the init_count?
> 
> I clearly don't prefer having of_find_compatible_node in PHY driver code. If
> you can find something without using that, it would be good.
> 
> Maybe create an API in phy-core that invokes the call-backs without caring
> about the ref count and implement some sort of mutual exclusivity in your
> driver? However this needs to be reviewed and discussed.

Thanks for your feedback. This feature (usb cluster) is a nice to have
for the Armada 375 SoC, but is not mandatory for the USB support on
this SoC.

As I don't want to postpone the merge of the USB support for this. I
will resend a new patch series, without the usb-cluster support, to be
merged in 3.16 kernel. And in the same time I will submit a new series
with an extension of the phy-core API. if everything goes well, then
it will be also merged in 3.16, else it will be in the next release.

Thanks again for your time,

Gregory

-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com