linux-kernel - Re: [PATCH v4 2/3] Broadcom USB DRD Phy driver for Northstar2

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Message-ID: <5f6d688b-7bbc-7b3c-2be8-fcea7853aae3@ti.com>
Date:   Wed, 5 Apr 2017 19:04:48 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Raviteja Garimella <raviteja.garimella@...adcom.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        Jon Mason <jonmason@...adcom.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/3] Broadcom USB DRD Phy driver for Northstar2

Hi Ravi,

On Wednesday 05 April 2017 06:30 PM, Raviteja Garimella wrote:
> Hi Kishon,
> 
> On Wed, Apr 5, 2017 at 4:30 PM, Kishon Vijay Abraham I <kishon@...com> wrote:
>> Hi,
>>
>> On Tuesday 28 March 2017 05:57 PM, Raviteja Garimella wrote:
>>> This is driver for USB DRD Phy used in Broadcom's Northstar2
>>> SoC. The phy can be configured to be in Device mode or Host
>>> mode based on the type of cable connected to the port. The
>>> driver registers to  extcon framework to get appropriate
>>> connect events for Host/Device cables connect/disconnect
>>> states based on VBUS and ID interrupts.
>>
>> $patch should be phy: phy-bcm-ns2-usbdrd: USB DRD Phy driver for Broadcoms
>> Northstar2.
>>
> 
> Will do.
> 
>> Sorry for not letting you know this earlier. But I feel the design of the
>> driver should be changed. Extcon shouldn't be used here. The extcon
>> notifications should be sent to the consumer driver and the consumer driver
>> should be responsible for invoking the phy ops.
>>
> 
> The consumer drivers here would be a UDC driver (USB device
> controller), EHCI and OHCI host controller drivers.
> I was already suggested in UDC driver review to deal with extcon in Phy driver.
> 
> This phy connects to 2 host controllers, and one device controller.
> That's the design in Broadcom Northstar2
> platform. The values of the VBUS and ID pins of this port are
> determined based on the type of the cable (device cable
> or host cable). And. phy has to be configured accordingly.
> 
>> The phy ops being invoked during extcon events doesn't look right.
> 
> Could you please elaborate on the concern, so that we can think of
> mitigating those issues in this driver?
> Since we are dealing with phy init/shutdown in this driver itself, are
> you okay with moving the extcon handling code
> out of phy ops ?

yeah, For e.g., ns2_drd_phy_init is part of phy_ops and is being invoked from
extcon events too. Can a phy which is initialized by a phy consumer (say your
UDC invokes phy_init) can be shutdown by an extcon event?

Maybe a clear explanation of when phy_ops here will be invoked and when it will
set using extcon events might help.

Thanks
Kishon