linux-kernel - Re: [PATCH V3 4/4] soc/tegra: pmc: Use the new reset APIs to manage reset controllers

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Date:   Tue, 25 Apr 2017 23:20:08 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        Stephen Warren <swarren@...dotorg.org>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        Linux USB Mailing List <linux-usb@...r.kernel.org>,
        "thierry.reding" <thierry.reding@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org, Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH V3 4/4] soc/tegra: pmc: Use the new reset APIs to manage
 reset controllers

On Tue, Apr 25, 2017 at 4:41 PM, Jon Hunter <jonathanh@...dia.com> wrote:
>
> On 25/04/17 12:06, Vivek Gautam wrote:
>> On 04/25/2017 04:24 PM, Jon Hunter wrote:
>>> On 25/04/17 11:33, Philipp Zabel wrote:
>>>> On Tue, 2017-04-25 at 11:05 +0100, Jon Hunter wrote:
>>>>> On 25/04/17 05:15, Vivek Gautam wrote:
>>>>>> On 04/24/2017 06:15 PM, Jon Hunter wrote:
>>>>>>> On 18/04/17 12:21, Vivek Gautam wrote:
>>>>>>>> Make use of reset_control_array_*() set of APIs to manage
>>>>>>>> an array of reset controllers available with the device.
>>>>>>> Before we apply this patch, I need to check to see if the order of
>>>>>>> the
>>>>>>> resets managed by the PMC driver matter. Today the order of the
>>>>>>> resets
>>>>>>> is determined by the order they appear in the DT node and although
>>>>>>> the
>>>>>>> new APIs work in the same way they do not guarantee this. So let me
>>>>>>> check to see if we can any concerns about ordering here. Otherwise
>>>>>>> would
>>>>>>> be nice to use these APIs.
>>>>>> Right, that will be perfect.
>>>>> So I don't see any restrictions here and so I think this change is
>>>>> fine.
>>>> Thank you for checking.
>>>>
>>>>> BTW, for the DT case, is there any reason why we don't just say the
>>>>> order will be determine by the order the resets are list in the DT
>>>>> node?
>>>> I'd rather not make any promises, so I don't have to care about keeping
>>>> them. This makes it easier to think about and allows for more freedom in
>>>> changing the core code if needed.
>>>>
>>>> What if in the future there is a use case for enabling a bunch of resets
>>>> by flipping a number of bits in a single register at the same time? Or
>>>> if people accidentally depend on the ordering when in reality there is a
>>>> small delay necessary between assertions that just happens to be hidden
>>>> by the framework overhead?
>>>>
>>>> If there is a use case for an array of reset controls that must be
>>>> (de)asserted in a fixed order and doesn't need any delay between the
>>>> steps and is not suitable to be described by named resets for some
>>>> reason, we can discuss this. Until then, I'm happy that tegra pmc can
>>>> handle arrays without any particular ordering.
>>> OK, makes sense.
>>
>> Thanks Jon for testing this.
>
> Not tested yet :-)
>
> However, I will test this just to confirm. Are you planning on sending
> out a v4 soon?

Yes, I will send a v4 soon this week.

Thanks
Vivek


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