linux-kernel - Re: [PATCH 5/5] pwm: pwm-tiehrpwm: Update dt binding document to use generic node name

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Date:	Thu, 17 Mar 2016 13:56:16 -0500
From:	Rob Herring <robh@...nel.org>
To:	"Franklin S Cooper Jr." <fcooper@...com>
Cc:	Thierry Reding <thierry.reding@...il.com>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Benoit Cousson <bcousson@...libre.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Tero Kristo <t-kristo@...com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Linux PWM List <linux-pwm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-omap <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 5/5] pwm: pwm-tiehrpwm: Update dt binding document to use
 generic node name

On Thu, Mar 17, 2016 at 1:20 PM, Franklin S Cooper Jr. <fcooper@...com> wrote:
>
>
> On 03/17/2016 01:00 PM, Rob Herring wrote:
>> On Thu, Mar 17, 2016 at 11:49 AM, Franklin S Cooper Jr. <fcooper@...com> wrote:
>>>
>>> On 03/17/2016 10:03 AM, Rob Herring wrote:
>>>> On Mon, Mar 07, 2016 at 01:51:58PM -0600, Franklin S Cooper Jr wrote:
>>>>> Now that the node name has been changed from ehrpwm to pwm the document
>>>>> should show this proper usage. Also change the unit address in the example
>>>>> from 0 to the proper physical address value that should be used.
>>>>>
>>>>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
>>>>> ---
>>>>>  Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt | 4 ++--
>>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt b/Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt
>>>>> index 9c100b2..20211ed 100644
>>>>> --- a/Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt
>>>>> +++ b/Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt
>>>>> @@ -15,14 +15,14 @@ Optional properties:
>>>>>
>>>>>  Example:
>>>>>
>>>>> -ehrpwm0: ehrpwm@0 { /* EHRPWM on am33xx */
>>>>> +ehrpwm0: pwm@...00200 { /* EHRPWM on am33xx */
>>>>>      compatible = "ti,am33xx-ehrpwm";
>>>>>      #pwm-cells = <3>;
>>>>>      reg = <0x48300200 0x100>;
>>>>>      ti,hwmods = "ehrpwm0";
>>>>>  };
>>>>>
>>>>> -ehrpwm0: ehrpwm@0 { /* EHRPWM on da850 */
>>>>> +ehrpwm0: pwm@...00000 { /* EHRPWM on da850 */
>>>> No leading 0s, but more importantly the address is wrong.
>>> I will remove the leading 0. However, this value was taken
>>> from the .dtsi and I just double checked and I see the same
>>> value in the datasheet. I believe DA850,OMAP-L138 and AM18x
>>> all have the same memory mapping. I'm looking at
>>> http://www.ti.com/lit/ds/symlink/am1808.pdf page 233 and the
>>> addresses match up what is seen here and in the .dtsi.
>>>
>>> Can you point me to which document your looking at that
>>> shows a different value?
>> Ummm, ...
>>
>>>>>      compatible = "ti,da850-ehrpwm", "ti,am33xx-ehrpwm";
>>>>>      #pwm-cells = <3>;
>>>>>      reg = <0x300000 0x2000>;
>> right here.
>
> So I don't know the history but the SOC node specifies a
> ranges value of ranges = <0x0 0x01c00000 0x400000>;. It
> seems that all child nodes of SOC have a reg property then
> is based on an offset of 0x01c00000. So this is true for
> UART, rtc, i2c, wdt, mmc, spi etc... So using a base offset
> of 0x01c00000 + 0x300000 (reg value of the pwm) equals the
> physical address of the ehrpwm0 register 0x1f00000.
>
> For the child nodes within the SOC node, the unit-address is
> always based on the physical address not based on the offset
> address.

They are all wrong and should be fixed. Unit address should match the
reg property unless the bus has defined something different (e.g.
PCI).

Rob