Re: [PATCH] rtc: omap: Support scratch registers

[Keerthy]

On Wednesday 08 November 2017 02:01 PM, Keerthy wrote:
> 
> 
> On Wednesday 08 November 2017 01:51 PM, Alexandre Belloni wrote:
>> On 08/11/2017 at 13:36:15 +0530, Keerthy wrote:
>>>
>>>
>>> On Wednesday 08 November 2017 12:46 PM, Alexandre Belloni wrote:
>>>> On 08/11/2017 at 12:38:05 +0530, Keerthy wrote:
>>>>>
>>>>>
>>>>> On Wednesday 08 November 2017 11:57 AM, Alexandre Belloni wrote:
>>>>>> Hi,
>>>>>>
>>>>>> On 08/11/2017 at 11:30:45 +0530, Keerthy wrote:
>>>>>>>>>> +static int omap_rtc_scratch_read(void *priv, unsigned int offset, void *_val,
>>>>>>>>>> +				 size_t bytes)
>>>>>>>>>> +{
>>>>>>>>>> +	struct omap_rtc	*rtc = priv;
>>>>>>>>>> +	u32 *val = _val;
>>>>>>>>>> +	int i;
>>>>>>>>>> +
>>>>>>>>>> +	for (i = 0; i < bytes / 4; i++)
>>>>>>>>>> +		val[i] = rtc_readl(rtc,
>>>>>>>>>> +				   OMAP_RTC_SCRATCH0_REG + offset + (i * 4));
>>>>>>>
>>>>>>> Can the offset be the Scratch register number instead of bytes offset?
>>>>>>> More intuitive to me.
>>>>>>>
>>>>>>> So that one can request using offset as 0, 1, 2 instead of 0, 4, 8?
>>>>>>>
>>>>>>
>>>>>> Well, the offset is coming from the nvmem core, itself getting it from
>>>>>> the Linux file API (and it is in bytes). However, you have the guarantee
>>>>>> that it will be aligned on a word, see:
>>>>>> http://elixir.free-electrons.com/linux/latest/source/drivers/nvmem/core.c#L88
>>>>>
>>>>> Okay Alexandre. Thanks for clarifying. Looks good to me.
>>>>> I have tested on AM437X-GP-EVM.
>>>>>
>>>>
>>>> If needed, you can define nvmem cells (and I guess that is what you
>>>> want):
>>>> http://elixir.free-electrons.com/linux/latest/source/Documentation/devicetree/bindings/nvmem/nvmem.txt
>>>
>>> With this patch we cannot still use nvmem_device_write and
>>> nvmem_device_read as the nvmem_device is still not registered.
>>>
>>> How can a driver write to scratch pad registers? Should we be calling
>>> nvmem_register in the probe?
>>
>> It is not needed, it is registered by rtc_nvmem_register().
> 
> Let me go through the chain:
> 
> rtc_register_device -> __rtc_register_device --> rtc_nvmem_register ->
> rtc_nvram_register
> 
> I am seeing that for rtc-omap driver there is rtc_register_device call

I mean there NO rtc_register_device call.

> and i see that rtc_nvmem_register is not getting called.
> 
> Should we add rtc_register_device in probe of rtc-omap?
> 
>>
>> nvmem_device_read/write are working because that is what I'm using to
>> implement the old sysfs ABI with rtc_nvram_read/write.
>>