Re: [PATCH 4/5] pwm: pwm-tipwmss: Update documentation to use empty range property

From: "Franklin S Cooper Jr." <fcooper@ti.com>
To: Rob Herring <robh@kernel.org>
Cc: <thierry.reding@gmail.com>, <pawel.moll@arm.com>,
	<mark.rutland@arm.com>, <ijc+devicetree@hellion.org.uk>,
	<galak@codeaurora.org>, <bcousson@baylibre.com>,
	<tony@atomide.com>, <linux@arm.linux.org.uk>, <t-kristo@ti.com>,
	<mturquette@baylibre.com>, <sboyd@codeaurora.org>,
	<linux-pwm@vger.kernel.org>, <devicetree@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <linux-omap@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-clk@vger.kernel.org>
Subject: Re: [PATCH 4/5] pwm: pwm-tipwmss: Update documentation to use empty range property
Date: Thu, 17 Mar 2016 16:29:39 -0500	[thread overview]
Message-ID: <56EB21C3.8000806@ti.com> (raw)
In-Reply-To: <56EAE1BD.9040601@ti.com>


On 03/17/2016 11:56 AM, Franklin S Cooper Jr. wrote:
>
> On 03/17/2016 10:01 AM, Rob Herring wrote:
>> On Mon, Mar 07, 2016 at 01:51:57PM -0600, Franklin S Cooper Jr wrote:
>>> Since the PWMSS and its subdevices (eCAP and ePWM) use the same address
>>> space then the range property should be empty. Update the documentation
>>> to show the correct usage.
>> Why does it matter? An empty ranges is generally not preferred.
> Someone pointed out that ranges should probably be empty. I
> double checked it with what is in the ePAPR doc and based on
> the definition it should be set to empty. I also checked
> against the am33xx.dtsi and saw that both USB and ethernet
> uses an empty value for ranges.
>
> Can you elaborate on why this isn't preferable?

I'm going to drop this patch and the previous patch for now
that messes with the ranges property. I can resubmit them
separately later on if that is the route we decide to take.
>
>>> Signed-off-by: Franklin S Cooper Jr <fcooper@ti.com>
>>> ---
>>>  Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt | 12 ++++--------
>>>  1 file changed, 4 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt b/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt
>>> index f7eae77..672fa71 100644
>>> --- a/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt
>>> +++ b/Documentation/devicetree/bindings/pwm/pwm-tipwmss.txt
>>> @@ -7,11 +7,9 @@ Required properties:
>>>  		  Should set to 1.
>>>  - size-cells: specify number of u32 entries needed to specify child nodes size
>>>  		in reg property. Should set to 1.
>>> -- ranges: describes the address mapping of a memory-mapped bus. Should set to
>>> -	   physical address map of child's base address, physical address within
>>> -	   parent's address  space and length of the address map. For am33xx,
>>> -	   3 set of child register maps present, ECAP register space, EQEP
>>> -	   register space, EHRPWM register space.
>>> +- ranges: describes the address mapping of a memory-mapped bus. Its value
>>> +	  should be empty since no address translation is needed between the
>>> +	  parent and the child.
>>>  
>>>  Also child nodes should also populated under PWMSS DT node.
>>>  
>>> @@ -23,9 +21,7 @@ pwmss0: pwmss@48300000 {
>>>  	#address-cells = <1>;
>>>  	#size-cells = <1>;
>>>  	status = "disabled";
>>> -	ranges = <0x48300100 0x48300100 0x80   /* ECAP */
>>> -		  0x48300180 0x48300180 0x80   /* EQEP */
>>> -		  0x48300200 0x48300200 0x80>; /* EHRPWM */
>>> +	ranges;
>>>  
>>>  	/* child nodes go here */
>>>  };
>>> -- 
>>> 2.7.0
>>>
> --
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