Re: [PATCH v5 02/11] phy: exynos-ufs: add UFS PHY driver for EXYNOS SoC

Alim Akhtar
2017-02-28T08:21:04Z

Hi Kishon,

On 02/28/2017 09:04 AM, Kishon Vijay Abraham I wrote:
> Hi,
>
> On Monday 27 February 2017 07:40 PM, Alim Akhtar wrote:
>> Hi Kishon,
>>
>> On 02/27/2017 10:56 AM, Kishon Vijay Abraham I wrote:
>>> Hi,
>>>
>>> On Thursday 23 February 2017 12:20 AM, Alim Akhtar wrote:
>>>> On Fri, Feb 3, 2017 at 2:49 PM, Alim Akhtar <alim.akhtar@samsung.com> wrote:
>>>>> Hi Kishon,
>>>>>
>>>>>
>>>>> On 11/19/2015 07:09 PM, Kishon Vijay Abraham I wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On Tuesday 17 November 2015 01:41 PM, Alim Akhtar wrote:
>>>>>>>
>>>>>>> Hi
>>>>>>> Thanks again for looking into this.
>>>>>>>
>>>>>>> On 11/17/2015 11:46 AM, Kishon Vijay Abraham I wrote:
>>>>>>>>
>>>>>>>> Hi,
>>>>>>>>
>>>>>>>> On Monday 09 November 2015 10:56 AM, Alim Akhtar wrote:
>>>>>>>>>
>>>>>>>>> From: Seungwon Jeon <essuuj@gmail.com>
>>>>>>>>>
>>>>>>>>> This patch introduces Exynos UFS PHY driver. This driver
>>>>>>>>> supports to deal with phy calibration and power control
>>>>>>>>> according to UFS host driver's behavior.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Seungwon Jeon <essuuj@gmail.com>
>>>>>>>>> Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
>>>>>>>>> Cc: Kishon Vijay Abraham I <kishon@ti.com>
>>>>>>>>> ---
>>>>>>>>> drivers/phy/Kconfig | 7 ++
>>>>>>>>> drivers/phy/Makefile | 1 +
>>>>>>>>> drivers/phy/phy-exynos-ufs.c | 241
>>>>>>>>> ++++++++++++++++++++++++++++++++++++
>>>>>>>>> drivers/phy/phy-exynos-ufs.h | 85 +++++++++++++
>>>>>>>>> drivers/phy/phy-exynos7-ufs.h | 89 +++++++++++++
>>>>>>>>> include/linux/phy/phy-exynos-ufs.h | 85 +++++++++++++
>>>>>>>>> 6 files changed, 508 insertions(+)
>>>>>>>>> create mode 100644 drivers/phy/phy-exynos-ufs.c
>>>>>>>>> create mode 100644 drivers/phy/phy-exynos-ufs.h
>>>>>>>>> create mode 100644 drivers/phy/phy-exynos7-ufs.h
>>>>>>>>> create mode 100644 include/linux/phy/phy-exynos-ufs.h
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
>>>>>>>>> index 7eb5859dd035..7d38a92e0297 100644
>>>>>>>>> --- a/drivers/phy/Kconfig
>>>>>>>>> +++ b/drivers/phy/Kconfig
>>>>>>>>> @@ -389,4 +389,11 @@ config PHY_CYGNUS_PCIE
>>>>>>>>> Enable this to support the Broadcom Cygnus PCIe PHY.
>>>>>>>>> If unsure, say N.
>>>>>>>>>
>>>>>>>>> +config PHY_EXYNOS_UFS
>>>>>>>>> + tristate "EXYNOS SoC series UFS PHY driver"
>>>>>>>>> + depends on OF && ARCH_EXYNOS || COMPILE_TEST
>>>>>>>>> + select GENERIC_PHY
>>>>>>>>> + help
>>>>>>>>> + Support for UFS PHY on Samsung EXYNOS chipsets.
>>>>>>>>> +
>>>>>>>>> endmenu
>>>>>>>>> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
>>>>>>>>> index 075db1a81aa5..9bec4d1a89e1 100644
>>>>>>>>> --- a/drivers/phy/Makefile
>>>>>>>>> +++ b/drivers/phy/Makefile
>>>>>>>>> @@ -10,6 +10,7 @@ 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
>>>>>>>>> +obj-$(CONFIG_PHY_EXYNOS_UFS) += phy-exynos-ufs.o
>>>>>>>>> obj-$(CONFIG_PHY_LPC18XX_USB_OTG) += phy-lpc18xx-usb-otg.o
>>>>>>>>> obj-$(CONFIG_PHY_PXA_28NM_USB2) += phy-pxa-28nm-usb2.o
>>>>>>>>> obj-$(CONFIG_PHY_PXA_28NM_HSIC) += phy-pxa-28nm-hsic.o
>>>>>>>>> diff --git a/drivers/phy/phy-exynos-ufs.c
>>>>>>>>> b/drivers/phy/phy-exynos-ufs.c
>>>>>>>>> new file mode 100644
>>>>>>>>> index 000000000000..cb1aeaa3d4eb
>>>>>>>>> --- /dev/null
>>>>>>>>> +++ b/drivers/phy/phy-exynos-ufs.c
>>>>>>>>> @@ -0,0 +1,241 @@
>>>>>>>>> +/*
>>>>>>>>> + * UFS PHY driver for Samsung EXYNOS SoC
>>>>>>>>> + *
>>>>>>>>> + * Copyright (C) 2015 Samsung Electronics Co., Ltd.
>>>>>>>>> + * Author: Seungwon Jeon <essuuj@gmail.com>
>>>>>>>>> + *
>>>>>>>>> + * This program is free software; you can redistribute it and/or
>>>>>>>>> modify
>>>>>>>>> + * it under the terms of the GNU General Public License as published
>>>>>>>>> by
>>>>>>>>> + * the Free Software Foundation; either version 2 of the License, or
>>>>>>>>> + * (at your option) any later version.
>>>>>>>>> + */
>>>>>>>>> +#include <linux/clk.h>
>>>>>>>>> +#include <linux/delay.h>
>>>>>>>>> +#include <linux/err.h>
>>>>>>>>> +#include <linux/io.h>
>>>>>>>>> +#include <linux/iopoll.h>
>>>>>>>>> +#include <linux/mfd/syscon.h>
>>>>>>>>> +#include <linux/module.h>
>>>>>>>>> +#include <linux/of.h>
>>>>>>>>> +#include <linux/phy/phy.h>
>>>>>>>>> +#include <linux/phy/phy-exynos-ufs.h>
>>>>>>>>> +#include <linux/platform_device.h>
>>>>>>>>> +#include <linux/regmap.h>
>>>>>>>>> +
>>>>>>>>> +#include "phy-exynos-ufs.h"
>>>>>>>>> +
>>>>>>>>> +#define for_each_phy_lane(phy, i) \
>>>>>>>>> + for (i = 0; i < (phy)->lane_cnt; i++)
>>>>>>>>> +#define for_each_phy_cfg(cfg) \
>>>>>>>>> + for (; (cfg)->id; (cfg)++)
>>>>>>>>> +
>>>>>>>>> +#define PHY_DEF_LANE_CNT 1
>>>>>>>>> +
>>>>>>>>> +static void exynos_ufs_phy_config(struct exynos_ufs_phy *phy,
>>>>>>>>> + const struct exynos_ufs_phy_cfg *cfg, u8 lane)
>>>>>>>>> +{
>>>>>>>>> + enum {LANE_0, LANE_1}; /* lane index */
>>>>>>>>> +
>>>>>>>>> + switch (lane) {
>>>>>>>>> + case LANE_0:
>>>>>>>>> + writel(cfg->val, (phy)->reg_pma + cfg->off_0);
>>>>>>>>> + break;
>>>>>>>>> + case LANE_1:
>>>>>>>>> + if (cfg->id == PHY_TRSV_BLK)
>>>>>>>>> + writel(cfg->val, (phy)->reg_pma + cfg->off_1);
>>>>>>>>> + break;
>>>>>>>>> + }
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +static bool match_cfg_to_pwr_mode(u8 desc, u8 required_pwr)
>>>>>>>>> +{
>>>>>>>>> + if (IS_PWR_MODE_ANY(desc))
>>>>>>>>> + return true;
>>>>>>>>> +
>>>>>>>>> + if (IS_PWR_MODE_HS(required_pwr) && IS_PWR_MODE_HS_ANY(desc))
>>>>>>>>> + return true;
>>>>>>>>> +
>>>>>>>>> + if (COMP_PWR_MODE(required_pwr, desc))
>>>>>>>>> + return true;
>>>>>>>>> +
>>>>>>>>> + if (COMP_PWR_MODE_MD(required_pwr, desc) &&
>>>>>>>>> + COMP_PWR_MODE_GEAR(required_pwr, desc) &&
>>>>>>>>> + COMP_PWR_MODE_SER(required_pwr, desc))
>>>>>>>>> + return true;
>>>>>>>>> +
>>>>>>>>> + return false;
>>>>>>>>> +}
>>>>>>>>> +
>>>>>>>>> +int exynos_ufs_phy_calibrate(struct phy *phy,
>>>>>>>>> + enum phy_cfg_tag tag, u8 pwr)
>>>>>>>>
>>>>>>>>
>>>>>>>> This is similar to the first version of your patch without
>>>>>>>> EXPORT_SYMBOL.
>>>>>>>>
>>>>>>>> I think you have to create a new generic PHY_OPS for calibrate PHY while
>>>>>>>> making
>>>>>>>> sure that it is as generic as possible (which means calibrate_phy
>>>>>>>> shouldn't
>>>>>>>> have tag and pwr arguments or a strong justification as to why those
>>>>>>>> arguments
>>>>>>>> are required in a generic API).
>>>>>>>
>>>>>>> I don't see the advantage to making this a generic phy_ops, this is
>>>>>>> exynos
>>>>>>> specific ufs-phy, please have a look at other implementations
>>>>>>
>>>>>>
>>>>>> only the implementation is specific to exynos. I've seen lot of other
>>>>>> vendors
>>>>>> want to do something like calibrate phy.
>>>>>>
>>>>>> So if we add something like (*calibrate)(struct phy *phy), then it can be
>>>>>> used
>>>>>> by others as well. Russell King also want to minimize the code to program
>>>>>> calibration settings. So it would be good to come up with a set of
>>>>>> standard
>>>>>> bindings like 'phy,tx-swing', 'phy,emphasis', 'phy,amplitude' etc.. to
>>>>>> program
>>>>>> these settings.
>>>>>>>
>>>>>>> drivers/phy/phy-qcom-ufs.c (which I belive mereged recently)
>>>>>>
>>>>>>
>>>>>> Thats why I hate when someone else merge PHY drivers :-( That driver can
>>>>>> as
>>>>>> well be in drivers/misc as it doesn't use PHY framework as it is supposed
>>>>>> to be
>>>>>> used. It just exports a dozen of API's to be used by controller drivers.
>>>>>> ick..
>>>>>>
>>>>>>> may be other vendors might come with there own implementation of phy.
>>>>>>
>>>>>>
>>>>>> right, it's all about providing the correct callback functions.
>>>>>>>
>>>>>>> I am using what is currently provided by the generic phy framework.
>>>>>>
>>>>>>
>>>>>> I think for your use case, what is currently provided in the PHY framework
>>>>>> is
>>>>>> not sufficient.
>>>>>>
>>>>> Its little over a year since last time we discuss about adding a generic
>>>>> calibration API. I can see in the past people tried adding *calibration* API
>>>>> [1] but not sure why [1] was not landed in mainline.
>>>>> Anyway now we have many users of phy_calibration API, like UFS, USB and may
>>>>> be PCIe, there is a real need to add this functionality. So, here is my
>>>>> approach:
>>>
>>> Agree, there are quite a few users that require calibration of phy parameters.
>>> I think previously it was accommodated in phy_init, hence it was not merged.
>> Ok, thanks for this information.
>>
>>>>> * Along with [1], we can add a void *priv for handling device specific phy
>>>>> private data, and before calling phy_calibration() from phy consumer,
>>>>> phy->priv is populated with private data.
>>>
>>> Not sure how you plan to use priv here?
>>>
>> From ufs driver I am populating PHY _priv_ data and calling phy_calibrate()
>>
>> e.g
>> ----------------------- from ufs-exynos.c
>> Instead of using below code earlier
>> - exynos_ufs_phy_calibrate(generic_phy,CFG_PRE_INIT,PWR_MODE_ANY);
>>
>> Now I am using below from ufs-exynos driver
>>
>> + generic_phy->priv =(void*)CFG_PRE_INIT;
>> + phy_calibrate(generic_phy);
>>
>> and in drivers/phy/phy-exynos-ufs.c
>> using phy->priv in calibration function.
>
> Don't prefer passing of such private pointers between drivers. Why is this needed?
>
As already explained before, this is needed to pass the calibration
point (when you want to do the calibration?, like before init, after
init or before/after _mode_ change etc).

I Don't think we have much option here, if we want to make
phy_calibration generic enough.

We have few options:
1> One way is to have phy_calibration takes some argument like
calibration point (which was part of my v3~v5), but looking at the
current implementation of phy-qcom-ufs.c, this approach might not be
generic enough.

2> And using EXPORT_SYMBOL way is not encourage (as in my V1, even
though others in phy drivers uses it).

3> the current proposal of using _priv_ data.

Out of the above 3 option, I feel using _priv_ data is more generic way
(and most of the major sub-system in Linux uses it).

lets see what other people think about __priv__ approach.

Please suggest your prefer way to handle this.

> Thanks
> Kishon
>
>
>