From: Sekhar Nori <nsekhar@ti.com>
To: Felipe Balbi <balbi@kernel.org>,
Peter Chen <hzpeterchen@gmail.com>, <pawell@cadence.com>
Cc: <rogerq@ti.com>, <devicetree@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
<linux-usb@vger.kernel.org>, lkml <linux-kernel@vger.kernel.org>,
<adouglas@cadence.com>, <jbergsagel@ti.com>, <nm@ti.com>,
<sureshp@cadence.com>, <peter.chen@nxp.com>, <pjez@cadence.com>,
<kurahul@cadence.com>
Subject: Re: [RFC PATCH v2 08/15] usb:cdns3: Implements device operations part of the API
Date: Fri, 14 Dec 2018 17:50:55 +0530 [thread overview]
Message-ID: <7e6ac47e-61e4-ecd3-73d3-9b1be2d81479@ti.com> (raw)
In-Reply-To: <875zvwl585.fsf@linux.intel.com>
On 14/12/18 4:56 PM, Felipe Balbi wrote:
> Hi,
>
> Sekhar Nori <nsekhar@ti.com> writes:
>>>>>>> All this should be part of comments in code along with information about
>>>>>>> controller versions which suffer from the errata.
>>>>>>>
>>>>>>> Is there a version of controller available which does not have the
>>>>>>> defect? Is there a future plan to fix this?
>>>>>>>
>>>>>>> If any of that is yes, you probably want to handle this with runtime
>>>>>>> detection of version (like done with DWC3_REVISION_XXX macros).
>>>>>>> Sometimes the hardware-read versions themselves are incorrect, so its
>>>>>>> better to introduce a version specific compatible too like
>>>>>>> "cdns,usb-1.0.0" (as hinted to by Rob Herring as well).
>>>>>>>
>>>>>>
>>>>>> custom match_ep is used and works with all versions of the gen1
>>>>>> controller. Future (gen2) releases of the controller won’t have such
>>>>>> limitation but there is no plan to change current (gen1) functionality
>>>>>> of the controller.
>>>>>>
>>>>>> I will add comment before cdns3_gadget_match_ep function.
>>>>>> Also I will change cdns,usb3 to cdns,usb3-1.0.0 and add additional
>>>>>> cdns,usb3-1.0.1 compatible.
>>>>>>
>>>>>> cdns,usb3-1.0.1 will be for current version of controller which I use.
>>>>>> cdns,usb3-1.0.0 will be for older version - Peter Chan platform.
>>>>>> I now that I have some changes in controller, and one of them require
>>>>>> some changes in DRD driver. It will be safer to add two separate
>>>>>> version in compatibles.
>>>>>>
>>>>>
>>>>> Pawel, could we have correct register to show controller version? It is
>>>>> better we could version judgement at runtime instead of static compatible.
>>>>
>>>> Agree with detecting IP version at runtime.
>>>>
>>>> But please have some indication of version in compatible string too,
>>>
>>> why? Runtime detection by revision register should be the way to go if
>>> the HW provides it. Why duplicate the information in compatible string?
>>>
>>>> especially since you already know there is going to be another revision
>>>> of hardware. It has the advantage that one can easily grep to see which
>>>> hardware is running current version of controller without having access
>>>> to the hardware itself. Becomes useful later on when its time to
>>>> clean-up unused code when boards become obsolete or for requesting
>>>> testing help.
>>>
>>> This doesn't sound like a very strong argument, actually. Specially when
>>> you consider that, since driver will do revision checking based on
>>> revision register, you already have strings to grep. Moreover, we don't
>>> usually drop support just like that.
>>
>> AFAICS, it is impossible to know just by grep'ing if there is any
>> hardware still supported in kernel and using DWC3_REVISION_194A, for
>> example.
>
> but why do you even care?
When, for example, its coming in the way of some clean-up I am
attempting to do.
>
>> If we are never going to drop support for any revision, this does not
>> matter much.
>>
>> Also, once you have the controller supported behind PCI, then I guess
>> you are pretty much tied to having to read hardware revision at runtime.
>
> that's another argument *for* using runtime detection, not against it.
I know :). I should have stated that in last e-mail itself, I am okay
with just runtime detection.
Thanks,
Sekhar
next prev parent reply other threads:[~2018-12-14 12:21 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-18 10:08 [RFC PATCH v2 00/15] Introduced new Cadence USBSS DRD Driver Pawel Laszczak
2018-11-18 10:08 ` [RFC PATCH v2 01/15] usb:cdns3: add pci to platform driver wrapper Pawel Laszczak
2018-11-23 10:44 ` Roger Quadros
2018-11-18 10:08 ` [RFC PATCH v2 02/15] usb:cdns3: Device side header file Pawel Laszczak
2018-11-30 6:48 ` PETER CHEN
2018-12-02 19:27 ` Pawel Laszczak
2018-11-18 10:08 ` [RFC PATCH v2 03/15] dt-bindings: add binding for USBSS-DRD controller Pawel Laszczak
2018-11-23 10:53 ` Roger Quadros
2018-11-25 7:33 ` Pawel Laszczak
2018-12-04 22:41 ` Rob Herring
2018-12-06 10:26 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 04/15] usb:cdns3: Driver initialization code Pawel Laszczak
2018-11-23 11:35 ` Roger Quadros
2018-11-25 12:35 ` Pawel Laszczak
2018-12-04 9:09 ` Peter Chen
2018-12-06 7:00 ` Pawel Laszczak
2018-12-04 8:50 ` Peter Chen
2018-12-04 10:46 ` Roger Quadros
2018-12-05 8:57 ` Peter Chen
2018-12-06 9:31 ` Pawel Laszczak
2018-12-05 19:24 ` Pawel Laszczak
2018-12-05 19:42 ` Pawel Laszczak
2018-12-06 10:02 ` Pawel Laszczak
2018-11-30 7:32 ` Peter Chen
2018-12-02 20:34 ` Pawel Laszczak
2018-12-04 7:11 ` Peter Chen
2018-12-05 7:19 ` Pawel Laszczak
2018-12-05 8:55 ` Alan Douglas
2018-12-05 9:07 ` Peter Chen
2018-11-18 10:09 ` [RFC PATCH v2 05/15] usb:cdns3: Added DRD support Pawel Laszczak
2018-11-23 14:51 ` Roger Quadros
2018-11-26 7:23 ` Pawel Laszczak
2018-11-26 8:07 ` Roger Quadros
2018-11-26 8:39 ` Pawel Laszczak
2018-11-26 9:39 ` Roger Quadros
2018-11-26 10:09 ` Pawel Laszczak
2018-11-26 10:15 ` Roger Quadros
2018-11-27 11:29 ` Pawel Laszczak
2018-11-27 12:10 ` Roger Quadros
2018-12-04 9:18 ` Peter Chen
2018-12-06 7:25 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 06/15] usb:cdns3: Adds Host support Pawel Laszczak
2018-11-23 14:23 ` Roger Quadros
2018-11-26 8:24 ` Pawel Laszczak
2018-11-26 9:50 ` Roger Quadros
2018-11-26 10:17 ` Pawel Laszczak
2018-12-05 8:41 ` Peter Chen
2018-11-18 10:09 ` [RFC PATCH v2 07/15] usb:cdns3: Adds Device mode support - initialization Pawel Laszczak
2018-11-28 11:34 ` Roger Quadros
2018-11-28 11:40 ` Felipe Balbi
2018-11-30 4:20 ` PETER CHEN
2018-11-30 6:29 ` Pawel Laszczak
2018-11-30 14:36 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 08/15] usb:cdns3: Implements device operations part of the API Pawel Laszczak
2018-11-28 12:22 ` Roger Quadros
2018-12-01 11:11 ` Pawel Laszczak
2018-12-03 10:19 ` Pawel Laszczak
2018-12-10 2:12 ` Peter Chen
2018-12-11 11:26 ` Sekhar Nori
2018-12-11 19:49 ` Pawel Laszczak
2018-12-14 1:34 ` Peter Chen
2018-12-14 6:49 ` Pawel Laszczak
2018-12-14 10:39 ` Sekhar Nori
2018-12-14 10:47 ` Felipe Balbi
2018-12-14 11:13 ` Sekhar Nori
2018-12-14 11:26 ` Felipe Balbi
2018-12-14 12:20 ` Sekhar Nori [this message]
2018-12-14 12:30 ` Felipe Balbi
2018-12-16 13:31 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 09/15] usb:cdns3: EpX " Pawel Laszczak
2018-11-28 12:46 ` Roger Quadros
2018-12-01 13:30 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 10/15] usb:cdns3: Ep0 " Pawel Laszczak
2018-11-28 14:31 ` Roger Quadros
2018-12-02 10:34 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 11/15] usb:cdns3: Implements ISR functionality Pawel Laszczak
2018-11-28 14:54 ` Roger Quadros
2018-12-02 11:49 ` Pawel Laszczak
2018-12-02 12:52 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 12/15] usb:cdns3: Adds enumeration related function Pawel Laszczak
2018-11-28 15:50 ` Roger Quadros
2018-12-02 16:39 ` Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 13/15] usb:cdns3: Adds transfer " Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 14/15] usb:cdns3: Adds debugging function Pawel Laszczak
2018-11-18 10:09 ` [RFC PATCH v2 15/15] usb:cdns3: Feature for changing role Pawel Laszczak
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