Subject: Re: [PATCH v5 02/11] phy: exynos-ufs: add UFS PHY driver for EXYNOS SoC
To: Kishon Vijay Abraham I <kishon@ti.com>,
        Alim Akhtar <alim.akhtar@gmail.com>
Cc: linux-scsi@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "James E.J. Bottomley" <JBottomley@odin.com>,
        vinayak holikatti <vinholikatti@gmail.com>,
        Jaehoon Chung <jh80.chung@samsung.com>,
        Seungwon Jeon <essuuj@gmail.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        Pankaj Dubey <pankaj.dubey@samsung.com>, vivek.gautam@codeaurora.org,
        subhashj@codeaurora.org
From: Alim Akhtar <alim.akhtar@samsung.com>
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Date: Mon, 06 Mar 2017 17:12:41 +0530
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Hi Kishon

On 03/01/2017 10:07 AM, Kishon Vijay Abraham I wrote:
> Hi,
>
> On Tuesday 28 February 2017 01:51 PM, Alim Akhtar wrote:
>> 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.
>
> Generally calibration has to be done at a single point. Having to do
> calibration in multiple places seems to be specific to Exynos.
>
Ok, calibration as such in not Exynos specific, calibration point may be.
> Can implementing a small state machine in exynos driver help?
>
Sorry I didn't get you here. What do mean by implement a state machine? 
when it can be easy handled with the proposed generic _calibration_ 
method. Why to complicate the thing?

You said, you "don't prefer passing a _priv_ pointer between driver", 
can you please explain why? what is the potential problem do you see 
with _priv_ pointer?

Look at the current implementation of 
"drivers/phy/phy-qcom-ufs-qmp-14nm.c" they have used "specific ops for 
Phy" and that too with the EXPORT_SYMBOL, don't you think this can be 
correct if we have a generic phy_calibration call back?

CCed Subhash Jadavani (who is doing most of the Qcom UFS stuffs) to get 
his input as well.


> Thanks
> Kishon
>
>
>