linux-kernel - Re: [PATCH v2 2/5] phy: qcom: Add Qualcomm PCIe PHY

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Message-ID: <CAErSpo6Cv+XOjA+ddds4i4YXCC4f=igR4MTcRwFO5eWLg-=LVA@mail.gmail.com>
Date:	Fri, 22 May 2015 13:06:37 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Stanimir Varbanov <svarbanov@...sol.com>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Mark Rutland <mark.rutland@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Mathieu Olivari <mathieu@...eaurora.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Pratyush Anand <pratyush.anand@...il.com>
Subject: Re: [PATCH v2 2/5] phy: qcom: Add Qualcomm PCIe PHY

[+cc Jingoo, Pratyush]

On Fri, May 22, 2015 at 11:25 AM, Stanimir Varbanov
<svarbanov@...sol.com> wrote:
> On 05/20/2015 04:23 PM, Bjorn Helgaas wrote:
>> On Wed, May 20, 2015 at 8:08 AM, Kishon Vijay Abraham I <kishon@...com> wrote:
>>> Hi Bjorn,
>>>
>>>
>>> On Wednesday 20 May 2015 04:11 AM, Bjorn Helgaas wrote:
>>>>
>>>> On Mon, May 04, 2015 at 06:24:10PM +0300, Stanimir Varbanov wrote:
>>>>>
>>>>> On 05/04/2015 05:35 PM, Kishon Vijay Abraham I wrote:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> On Monday 04 May 2015 06:12 PM, Stanimir Varbanov wrote:
>>>>>>>
>>>>>>> Add a PCIe PHY driver used by PCIe host controller driver
>>>>>>> on Qualcomm SoCs like Snapdragon 805.
>>>>>>>
>>>>>>> Signed-off-by: Stanimir Varbanov <svarbanov@...sol.com>
>>>>>>> ---
>>>>>>>    drivers/phy/Kconfig         |    9 ++
>>>>>>>    drivers/phy/Makefile        |    1 +
>>>>>>>    drivers/phy/phy-qcom-pcie.c |  291
>>>>>>> +++++++++++++++++++++++++++++++++++++++++++
>>>>>>
>>>>>>
>>>>>> Why do you need a new PHY driver for this? Why not use the existing QCOM
>>>>>> PHY driver. I can see the registers used here in
>>>>>> phy-qcom-ufs-qmp-14nm.h?
>>>>>
>>>>>
>>>>> I agree that on first glance there are similarities, but I'm not sure
>>>>> does the PHYs are the same IP blocks. Or at least they are different
>>>>> revisions which have too many differences. So trying to combine them
>>>>> will lead to more code than now.
>>>>>
>>>>> Either way I will try to understand how many the differences are.
>>>>
>>>>
>>>> Ping, where are we with this?  Should I wait for something else, or are
>>>> you
>>>> convinced there's enough difference to warrant a new PHY driver, Kishon?
>>>
>>>
>>> I'd like to wait to see if Stanimir can use existing driver instead of
>>> creating a new driver.
>>
>> OK, I'm waiting for a v3 with either tweaks to the QCOM PHY driver, or
>> stronger justification as to why that's impossible.  It's hard to
>> quantify statements like "there are similarities, but there are too
>> many differences," so you might have to actually attempt a patch for
>> the QCOM code and we can see how ugly that would turn out to be.
>
> Kishon,
>
> I'm still checking the differences, sorry for the delay.
>
> Bjorn, is the pcie driver looks good enough to be merged?

I haven't looked at that (I was waiting until I could deal with the
whole series).  But it sounds like it would be useful to merge patches
3-5 by themselves?  I'll take a look at those.

It would be good to get Arnd and Rob to take a look, especially at the DT parts.

And Jingoo and Pratyush since you use the DesignWare core.

Bjorn
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