linux-kernel - Re: [v2, 1/4] ARM: davinci: da8xx-dt: Add ti-aemif lookup for clock matching

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Message-ID: <40a6fd6d-9107-1620-014a-fa2f22d5cc23@lechnology.com>
Date:   Tue, 3 Jan 2017 11:05:33 -0600
From:   David Lechner <david@...hnology.com>
To:     Sekhar Nori <nsekhar@...com>
Cc:     Karl Beldan <karl.beldan+oss@...il.com>,
        Axel Haslam <ahaslam@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        linux-kernel@...r.kernel.org,
        Bartosz Gołaszewski <bgolaszewski@...libre.com>,
        Alexandre Bailon <abailon@...libre.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [v2, 1/4] ARM: davinci: da8xx-dt: Add ti-aemif lookup for clock
 matching

On 01/03/2017 02:58 AM, Sekhar Nori wrote:
> On Monday 02 January 2017 01:34 PM, Sekhar Nori wrote:
>> On Saturday 31 December 2016 06:22 AM, David Lechner wrote:
>>> On 08/10/2016 06:00 AM, Karl Beldan wrote:
>>>> Many davinci boards (da830 and da850 families) don't have their clocks
>>>> in DT yet and won't be successful in getting an unnamed aemif clock
>>>> without explicitly registering them via clk_lookups, failing the
>>>> ti-aemif memory driver probe.
>>>>
>>>> The current aemif lookup entry resolving to the same clock:
>>>>     'CLK(NULL,               "aemif",        &aemif_clk)'
>>>> remains, as it is currently used (davinci_nand is getting a named clock
>>>> "aemif").
>>>>
>>>> This change will allow to switch from the mach-davinci aemif code to
>>>> the ti-aemif memory driver.
>>>>
>>>> Signed-off-by: Karl Beldan <kbeldan@...libre.com>
>>>> ---
>>>
>>> FYI, I can't boot LEGO MINDSTORMS EV3 (AM1908) with a v4.9 mainline
>>> kernel. I did a git bisect and traced it down to this patch. I'm
>>> guessing that simply reverting it will break other things.
>>>
>>> The problem is that &aemif_clk is a node in a linked list and points to
>>> itself, which creates an infinite loop when looking up the usb clocks
>>> that are later in the list.
>>>
>>> I thought there was a patch to fix this properly from one of the Bay
>>> Libre guys to fix this already, but I can't seem to find it at the
>>> moment. When it is found, it would be good to have it applied to the 4.9
>>> stable and 4.10 mainline trees.
>>
>> Yes, a patch was submitted. It is pending in my queue since I need to do
>> a few experiments myself to determine if its the best solution possible.
>> Thanks for the heads-up on need to mark it for v4.9 stable. Will do.
>
> The master branch of my tree should have the patch included. If you can
> test and confirm it works fine on the lego platform, it will be great.
>

Tested "ARM: davinci: da850: fix infinite loop in clk_set_rate()" 
working on LEGO Mindstorms with a 4.9.0 kernel.