linux-kernel - Re: [PATCH 1/2] tty: amba-pl011: add support for clock frequency setting via dt

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Date:	Sat, 9 Jul 2016 08:42:30 +0200
From:	Jorge Ramirez <jorge.ramirez-ortiz@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Michael Turquette <mturquette@...libre.com>,
	linux@...linux.org.uk, xuwei5@...ilicon.com
Cc:	guodong.xu@...aro.org, xinliang.liu@...aro.org,
	john.stultz@...aro.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] tty: amba-pl011: add support for clock frequency
 setting via dt

On 07/09/2016 02:43 AM, Stephen Boyd wrote:
> On 07/08/2016 05:23 PM, Michael Turquette wrote:
>> Quoting Jorge Ramirez (2016-07-08 14:39:50)
>>> On 07/08/2016 07:14 PM, Michael Turquette wrote:
>>>> Quoting Jorge Ramirez-Ortiz (2016-07-08 01:11:06)
>>>>> Allow to specify the clock frequency for any given port via the
>>>>> assigned-clock-rates device tree property.
>>>>>
>>>>> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
>>>>> Tested-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>
>>>>> ---
>>>>>    drivers/tty/serial/amba-pl011.c | 5 +++++
>>>>>    1 file changed, 5 insertions(+)
>>>>>
>>>>> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
>>>>> index 1b7331e..51867ab 100644
>>>>> --- a/drivers/tty/serial/amba-pl011.c
>>>>> +++ b/drivers/tty/serial/amba-pl011.c
>>>>> @@ -55,6 +55,7 @@
>>>>>    #include <linux/types.h>
>>>>>    #include <linux/of.h>
>>>>>    #include <linux/of_device.h>
>>>>> +#include <linux/clk/clk-conf.h>
>>>>>    #include <linux/pinctrl/consumer.h>
>>>>>    #include <linux/sizes.h>
>>>>>    #include <linux/io.h>
>>>>> @@ -2472,6 +2473,10 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
>>>>>           if (IS_ERR(uap->clk))
>>>>>                   return PTR_ERR(uap->clk);
>>>>>    
>>>>> +       ret = of_clk_set_defaults(dev->dev.of_node, false);
>>>> Change looks good to me, but with one question: should this change be
>>>> put into more generic code instead of in this specific driver? For
>>>> instance, we call of_clk_set_defaults from the following files:
>>>>
>>>> drivers/base/platform.c
>>>> drivers/i2c/i2c-core.c
>>>> drivers/spi/spi.c
>>>>
>>>> And Stephen posted a patch to do this for devices on the AMBA bus:
>>>>
>>>> https://patchwork.kernel.org/patch/6501691/
>>>>
>>>> Does Stephen's patch mean that you do not need patch #1?
>>> I did a quick test (replaced my changes with the patch above) and the
>>> console broke and the BT stack couldn't communicate to the device over
>>> the uart...I guess something else needs doing on top of Stephen's change.
>>>
>> Let's give Stephen a chance to respond. If he doesn't soon then I'm OK
>> to merge your two patches.
>>
>
> Yeah we need to restart that patch. It's been in my "pending" list for a
> year now it seems.
>
> Curious why it broke things, perhaps device probe is failing when it
> didn't fail before?
>

um, I retested again this morning and it is all good - I was also a bit 
surprised when things failed yesterday  (it seems one of the wires on my 
board was loose, sorry).

So AFAIC your patch addresses the issue in a much generic (better) way 
and there are no regressions on a HiKey board running a 4.4 kernel.