[RFC 08/11] ARM: dts: am33xx: Add prcm_resets node

[Dan Murphy]

Tony and Arnd

Thanks for the comments

On 04/29/2014 07:22 PM, Tony Lindgren wrote:
> * Arnd Bergmann <arnd at arndb.de> [140429 13:35]:
>> On Tuesday 29 April 2014 15:19:47 Dan Murphy wrote:
>>> + * AM33xx reset index for PRCM Module
>>> + *
>>> + * Copyright 2014 Texas Instruments Inc.
>>> + *
>>> + * This program is free software; you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + */
>>> +
>>> +#ifndef _DT_BINDINGS_RESET_TI_AM33XX_H
>>> +#define _DT_BINDINGS_RESET_TI_AM33XX_H
>>> +
>>> +#define RESET_DEVICE_RESET                     0
>>> +#define RESET_GFX_RESET                                1
>>> +#define RESET_PER_RESET                                2
>>> +
>>> +#endif
>> Interfaces like this should only be used if you can't use hardware
>> numbers, in general. If these numbers are in the data sheet, just
>> put them directly into the dts file, as we do for interrupt numbers,
>> gpio numbers, register offsets etc.
>>
>> If you have made them up to define an interface between the driver
>> and DT because there is no usable hardare ID, I'd suggest just using
>> a single file across all SoCs that have this driver, and have
>> a unified name space.
> Also, it's a bit unclear how the reset controller phandle is used
> referenced and used by the consumer device.. Maybe setting that up
> first in a Linux generic way is a good point starting point.
>
> Maybe something like this along the same way as clocks are set up
> (completely untested):
>
> &reset1 {
> 	iva_reset: reset1 {
> 		reg = /bits/ 8 <0>;
> 	};
> 	gfx_reset: reset1 {
> 		reg = /bits/ 8 <1>;
> 	};
> 	...
> };
>
> &iva {
> 	compatible = "ti,ivahd";
> 	resets = <&reset1 1>;
> 	...
> };

I had something very similar to this when I was developing this driver but moved away from this.

Following the clocks implementation I had a separate dtsi for resets for each device and had the data defined like so
for each SoC.

&prcm_resets {
       device_reset: device_reset {
               rstctrl_offs = <0x1104>;
               ctrl_bit-shift = <0>;
               rstst_offs      = <0x1114>;
               sts_bit-shift   = <0>;
       };

       gpu_reset: gpu_reset {
               rstctrl_offs = <0x0D00>;
               ctrl_bit-shift = <3>;
               rstst_offs      = <0x0D0C>;
               sts_bit-shift = <5>;
       };
};

And then any client interested in a specific reset driver would include this

resets = <&prcm_resets &gpu_reset>;
reset-names = "gpu_reset";

Our reset code would then retrieve the register data through the phandle instead of an index.

Thoughts?

Dan

> Regards,
>
> Tony


-- 
------------------
Dan Murphy