linux-kernel - Re: [PATCH] ARM: davinci: da850: Fix pwm name matching

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Date:   Wed, 2 Nov 2016 23:20:42 -0500
From:   David Lechner <david@...hnology.com>
To:     Sekhar Nori <nsekhar@...com>, Kevin Hilman <khilman@...nel.org>
Cc:     Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: davinci: da850: Fix pwm name matching

On 11/01/2016 05:31 AM, Sekhar Nori wrote:
> On Monday 31 October 2016 08:18 PM, David Lechner wrote:
>> On 10/31/2016 05:18 AM, Sekhar Nori wrote:
>>> On Tuesday 25 October 2016 11:24 PM, David Lechner wrote:
>>>> This fixes pwm name matching for DA850 familiy devices. When using
>>>> device
>>>> tree, the da850_auxdata_lookup[] table caused pwm devices to have the
>>>> exact
>>>> same name, which caused errors when trying to register the devices.
>>>>
>>>> The names for clock matching in da850_clks[] also have to be updated to
>>>> to exactly match in order for the clock lookup to work correctly.
>>>>
>>>> Signed-off-by: David Lechner <david@...hnology.com>
>>>> ---
>>>>
>>>> Tested working on LEGO MINDSTORMS EV3.
>>>>
>>>>
>>>>  arch/arm/mach-davinci/da850.c    | 10 +++++++---
>>>>  arch/arm/mach-davinci/da8xx-dt.c | 10 +++++-----
>>>>  2 files changed, 12 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/arch/arm/mach-davinci/da850.c
>>>> b/arch/arm/mach-davinci/da850.c
>>>> index ed3d0e9..6b78a8f 100644
>>>> --- a/arch/arm/mach-davinci/da850.c
>>>> +++ b/arch/arm/mach-davinci/da850.c
>>>> @@ -510,9 +510,13 @@ static struct clk_lookup da850_clks[] = {
>>>>      CLK("vpif",        NULL,        &vpif_clk),
>>>>      CLK("ahci_da850",        NULL,        &sata_clk),
>>>>      CLK("davinci-rproc.0",    NULL,        &dsp_clk),
>>>> -    CLK("ehrpwm",        "fck",        &ehrpwm_clk),
>>>> -    CLK("ehrpwm",        "tbclk",    &ehrpwm_tbclk),
>>>> -    CLK("ecap",        "fck",        &ecap_clk),
>>>> +    CLK("ehrpwm.0",        "fck",        &ehrpwm_clk),
>>>> +    CLK("ehrpwm.0",        "tbclk",    &ehrpwm_tbclk),
>>>> +    CLK("ehrpwm.1",        "fck",        &ehrpwm_clk),
>>>> +    CLK("ehrpwm.1",        "tbclk",    &ehrpwm_tbclk),
>>>> +    CLK("ecap.0",        "fck",        &ecap_clk),
>>>> +    CLK("ecap.1",        "fck",        &ecap_clk),
>>>> +    CLK("ecap.2",        "fck",        &ecap_clk),
>>>
>>> This has exposed a limitation of DaVinci clock framework. The struct clk
>>> are stored as a linked list themselves. So a node repeating in the table
>>> above will create a loop in the linked list. This is easily seen on the
>>> LCDK board. davinci_clk_disable_unused() never returns. PWMs are unused
>>> on that board.
>>>
>>> There is no "simple" solution to this AFAICS. One solution is to
>>> separate the iterator from the clock hardware structure and use struct
>>> clk_hw available in struct clk_lookup.
>>>
>>> Or move DaVinci to common clock framework. This is of course preferred
>>> but much more involved as all 6 supported SoCs have to be moved together.
>>>
>>> Thanks,
>>> Sekhar
>>>
>>>
>>
>> The simple solution for now could be to make child clocks for each of
>> these that simply enable the parent clock. e.g. ehrpwm0_clk and
>> ehpwm1_clk are children of ehrpwm_clk, etc.
>
> That sounds good. I saw the v2 patch you sent and it looks good. I
> noticed that aemif clock is repeated in da850.c too. That needs fixing.

Same with emac clock.

>> Looking at da830.c, it looks like the solution was to make multiple
>> clocks that use the same LPSC, but this does not seem right to me.
>
> The PWM clock definitions there are definitely wrong. It should be
> fixed. Looks like its been like that forever.
>
> Thanks,
> Sekhar
>