linux-kernel - Re: [PATCH/RFT v2 02/17] ARM: davinci: da8xx: Add CFGCHIP syscon platform declaration.

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Date:   Wed, 26 Oct 2016 14:26:07 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     David Lechner <david@...hnology.com>,
        Axel Haslam <ahaslam@...libre.com>
CC:     Greg KH <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>, <robh+dt@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Kevin Hilman <khilman@...libre.com>,
        Sergei Shtylyov <sshtylyov@...mvista.com>,
        <manjunath.goudar@...aro.org>, Mark Brown <broonie@...nel.org>,
        Alexandre Bailon <abailon@...libre.com>,
        <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH/RFT v2 02/17] ARM: davinci: da8xx: Add CFGCHIP syscon
 platform declaration.

On Tuesday 25 October 2016 09:23 PM, David Lechner wrote:
> Hi Sekhar,
> 
> On 10/25/2016 05:17 AM, Sekhar Nori wrote:
>> On Tuesday 25 October 2016 03:07 PM, Axel Haslam wrote:
>>> Hi Sekar,
>>>
>>> On Tue, Oct 25, 2016 at 10:10 AM, Sekhar Nori <nsekhar@...com> wrote:
>>>> On Monday 24 October 2016 10:16 PM, ahaslam@...libre.com wrote:
>>>>> From: David Lechner <david@...hnology.com>
>>>>>
>>>>> The CFGCHIP registers are used by a number of devices, so using a
>>>>> syscon
>>>>> device to share them. The first consumer of this will by the
>>>>> phy-da8xx-usb
>>>>> driver.
>>>>>
>>>>> Signed-off-by: David Lechner <david@...hnology.com>
>>>>> [Axel: minor fix: change id to -1]
>>>>
>>>> Can you please clarify this change? There could be other syscon devices
>>>> on the chip for other common registers. Why use the singular device-id?
>>>>
>>>
>>> in the case of non DT boot, the phy driver is looking for "syscon" :
>>>
>>> d_phy->regmap = syscon_regmap_lookup_by_pdevname("syscon");
>>>
>>> if we register the syscon driver with id = 0, the actual name of the
>>> syscon
>>> device will be "syscon.0" and the phy driver will fail to probe, because
>>> the strncmp match in the syscon driver (syscon_match_pdevname)
>>> will fail.
>>>
>>> should i change the phy driver instead?
>>
>> Yes, please. Forcing only one syscon region for the whole chip will be
>> too restrictive, I am pretty sure.
>>
>> Thanks,
>> Sekhar
>>
> 
> In the previous review, you requested that this be changed to -1 [1].
> 
> If we change it back to 0, it will also require reverting a patch to the
> phy driver that has already been merged[2].

Sigh. Sorry about going around in circles on this one. Lets go with what
you have. If and when there is a need for another syscon node, the
driver and platform code can be updated. At least we will know why the
change is being done at that time.

Thanks,
Sekhar