linux-kernel - Re: [PATCH v5 2/2] phy: zynqmp: Add phy driver for xilinx zynqmp phy core

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Date:   Mon, 21 Jan 2019 11:15:35 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Anurag Kumar Vulisha <anuragku@...inx.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "vivek.gautam@...eaurora.org" <vivek.gautam@...eaurora.org>
CC:     Michal Simek <michals@...inx.com>,
        "v.anuragkumar@...il.com" <v.anuragkumar@...il.com>,
        sundeep subbaraya <sundeep.lkml@...il.com>,
        Ajay Yugalkishore Pandey <APANDEY@...inx.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] phy: zynqmp: Add phy driver for xilinx zynqmp phy
 core

Hi Anurag,

On 17/01/19 9:39 PM, Anurag Kumar Vulisha wrote:
> Hi Kishon,
> 
>> -----Original Message-----
>> From: Kishon Vijay Abraham I [mailto:kishon@...com]
>> Sent: Wednesday, January 16, 2019 1:38 PM
>> To: Anurag Kumar Vulisha <anuragku@...inx.com>; robh+dt@...nel.org; Mark
>> Rutland <mark.rutland@....com>; vivek.gautam@...eaurora.org
>> Cc: Michal Simek <michals@...inx.com>; v.anuragkumar@...il.com; sundeep
>> subbaraya <sundeep.lkml@...il.com>; Ajay Yugalkishore Pandey
>> <APANDEY@...inx.com>; linux-kernel@...r.kernel.org; linux-arm-
>> kernel@...ts.infradead.org; devicetree@...r.kernel.org
>> Subject: Re: [PATCH v5 2/2] phy: zynqmp: Add phy driver for xilinx zynqmp phy core
>>
>> Hi,
>>
>> On 18/12/18 7:15 PM, Anurag Kumar Vulisha wrote:
>>> ZynqMP SoC has a Gigabit Transceiver with four lanes. All the high
>>> speed peripherals such as USB, SATA, PCIE, Display Port and Ethernet
>>> SGMII can rely on any of the four GT lanes for PHY layer. This patch
>>> adds driver for that ZynqMP GT core.
>>>
>>> Signed-off-by: Anurag Kumar Vulisha <anurag.kumar.vulisha@...inx.com>
>>> ---
>>> Changes in v5:
>>> 	1. No functional changes. Added missing Author name
>>>
>>> Changes in v4:
>>> 	1. Moved include/dt-bindings/phy/phy.h into patch 1 as suggested by
>>> 	   "Rob Herring"
>>>
>>> Changes in v3:
>>> 	1. Corrected the Documentation as suggested by "Vivek Gautam"
>>>
>>> Changes in v2:
>>> 	1. Fixed the compilation error when compiled phy-zynqmp.c as a module
>>> 	2. Added CONFIG_PM macro in phy-zynqmp.c driver
>>> ---
>>>  drivers/phy/Kconfig            |    8 +
>>>  drivers/phy/Makefile           |    1 +
>>>  drivers/phy/phy-zynqmp.c       | 1582
>> ++++++++++++++++++++++++++++++++++++++++
>>>  include/linux/phy/phy-zynqmp.h |   52 ++
>>>  4 files changed, 1643 insertions(+)
>>>  create mode 100644 drivers/phy/phy-zynqmp.c  create mode 100644
>>> include/linux/phy/phy-zynqmp.h
>>>
>>> diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig index
>>> 60f949e..7a3c900 100644
>>> --- a/drivers/phy/Kconfig
>>> +++ b/drivers/phy/Kconfig
>>> @@ -40,6 +40,14 @@ config PHY_XGENE
>>>  	help
>>>  	  This option enables support for APM X-Gene SoC multi-purpose PHY.
>>>
>>> +config PHY_XILINX_ZYNQMP
>>> +	tristate "Xilinx ZynqMP PHY driver"
>>> +	depends on ARCH_ZYNQMP
>>> +	select GENERIC_PHY
>>> +	help
>>> +	  Enable this to support ZynqMP High Speed Gigabit Transceiver
>>> +	  that is part of ZynqMP SoC.
>>> +
>>>  source "drivers/phy/allwinner/Kconfig"
>>>  source "drivers/phy/amlogic/Kconfig"
>>>  source "drivers/phy/broadcom/Kconfig"
>>> diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile index
>>> 0301e25..2335e85 100644
>>> --- a/drivers/phy/Makefile
>>> +++ b/drivers/phy/Makefile
>>> +/**
>>> +
>>> +/**
>>> + * xpsgtr_override_deemph - override PIPE TX de-emphasis
>>> + * @phy: pointer to phy
>>> + * @plvl: pre-emphasis level
>>> + * @vlvl: voltage swing level
>>> + *
>>> + * Return: None
>>> + */
>>> +void xpsgtr_override_deemph(struct phy *phy, u8 plvl, u8 vlvl) {
>>> +	struct xpsgtr_phy *gtr_phy = phy_get_drvdata(phy);
>>> +	struct xpsgtr_dev *gtr_dev = gtr_phy->data;
>>> +	static u8 pe[4][4] = { { 0x2, 0x2, 0x2, 0x2 },
>>> +			       { 0x1, 0x1, 0x1, 0xFF },
>>> +			       { 0x0, 0x0, 0xFF, 0xFF },
>>> +			       { 0xFF, 0xFF, 0xFF, 0xFF } };
>>> +
>>> +	writel(pe[plvl][vlvl],
>>> +	       gtr_dev->serdes + gtr_phy->lane * L0_TX_ANA_TM_18_OFFSET +
>>> +	       L0_TX_ANA_TM_18);
>>> +}
>>> +EXPORT_SYMBOL_GPL(xpsgtr_override_deemph);
>>
>> I thought I gave a feedback to get rid of export symbol. This will make the consumer
>> driver tied to this PHY driver.
>>
> 
> Thanks a lot for spending your time in reviewing this patch. With the current implementation,
> if phy-zynqmp.c driver is not compiled and consumer driver calls xpsgtr_override_deemph()
> routine, static inline function in phy-zynqmp.h gets called and error -ENODEV is returned. So,
> with the current implementation the consumer driver is already depending on phy-zynqmp.c
> driver. Please correct me if  my understanding is wrong

If the same consumer is used with 5 different PHYs, we would be adding 5
different APIs for PHY functionality. We would also like to avoid the compiling
out option if we use something like a multi_v7_defconfig where a single image
is used for multiple platforms.

Thanks
Kishon

> 
> Best Regards,
> Anurag Kumar Vulisha
>