Message-id: <12decf59-0486-9efd-63de-12fee95a8cea@samsung.com>
Date:   Tue, 28 Feb 2017 13:51:04 +0530
From:   Alim Akhtar <alim.akhtar@...sung.com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Alim Akhtar <alim.akhtar@...il.com>
Cc:     linux-scsi@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "James E.J. Bottomley" <JBottomley@...n.com>,
        vinayak holikatti <vinholikatti@...il.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Seungwon Jeon <essuuj@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Pankaj Dubey <pankaj.dubey@...sung.com>,
        vivek.gautam@...eaurora.org
Subject: Re: [PATCH v5 02/11] phy: exynos-ufs: add UFS PHY driver for EXYNOS SoC

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@...sung.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@...il.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@...il.com>
>>>>>>>>> Signed-off-by: Alim Akhtar <alim.akhtar@...sung.com>
>>>>>>>>> Cc: Kishon Vijay Abraham I <kishon@...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@...il.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
>
>
>

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