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

From: Franklin S Cooper Jr.
Date: Thu Mar 17 2016 - 17:30:41 EST




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@xxxxxx>
>>> ---
>>> 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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