linux-kernel - Re: [PATCH v5 1/6] ARM: at91: add TCB registers definitions

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Date:   Thu, 28 Jun 2018 21:55:41 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexander Dahl <ada@...rsis.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/6] ARM: at91: add TCB registers definitions

On 28/06/2018 20:34, Alexandre Belloni wrote:
> On 28/06/2018 17:15:39+0200, Daniel Lezcano wrote:
>> On 19/06/2018 23:19, Alexandre Belloni wrote:
>>> Add registers and bits definitions for the timer counter blocks found on
>>> Atmel ARM SoCs.
>>>
>>> Tested-by: Alexander Dahl <ada@...rsis.com>
>>> Tested-by: Andras Szemzo <szemzo.andras@...il.com>
>>> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
>>> ---
>>>  include/soc/at91/atmel_tcb.h | 216 +++++++++++++++++++++++++++++++++++
>>
>> Is the header necessary ? Can it be moved in the .c ?
>>
> 
> Ultimately, the clocksource driver will not be the only one to use it.
> There is the pwm driver that will be converted (it was converted in the
> first version of the series). and then there is a counter driver that
> will be submitted once the subsystem is upstreamed.

Ok.

>>>  1 file changed, 216 insertions(+)
>>>  create mode 100644 include/soc/at91/atmel_tcb.h
>>>
>>> diff --git a/include/soc/at91/atmel_tcb.h b/include/soc/at91/atmel_tcb.h
>>> new file mode 100644
>>> index 000000000000..3ed66031fc76
>>> --- /dev/null
>>
>> [ ... ]
>>
>>> +static inline struct clk *tcb_clk_get(struct device_node *node, int channel)
>>> +{
>>> +	struct clk *clk;
>>> +	char clk_name[] = "t0_clk";
>>> +
>>> +	clk_name[1] += channel;
>>
>> clever :)
>>
>>> +	clk = of_clk_get_by_name(node->parent, clk_name);
>>> +	if (!IS_ERR(clk))
>>> +		return clk;
>>> +
>>> +	return of_clk_get_by_name(node->parent, "t0_clk");
>>
>> Why do you want to return clk from t0_clk if another channel is
>> requested ? This is prone to error.
> 
> The newer TCBs only have one peripheral clocks. The current DT binding only
> have t0_clk in that case so whatever the channel, t0_clk is the correct
> one.
> 
>>
>> I would clarify that at the caller level, if tcb_clk_get fails then try
>> with channel zero.
> 
> This was hidden from the individual drivers by tclib but this can be
> open coded in the drivers.
> 
>>
>>> +}
>>> +
>>> +static inline int tcb_irq_get(struct device_node *node, int channel)
>>
>> no inline
>>
> 
> IIRC, removing the inline will make linking the kernel fail when there
> is more than 2 drivers using the TCBs but I'll try again. Or I can
> remove both those functions and open code as you suggest.

Yes, preferable to remove these functions.

>>> +{
>>> +	int irq;
>>> +
>>> +	irq = of_irq_get(node->parent, channel);
>>> +	if (irq > 0)
>>> +		return irq;
>>> +
>>> +	return of_irq_get(node->parent, 0);
>>
>> Same comment than above.
>>
>>> +}
>>> +
>>> +static const u8 atmel_tc_divisors[5] = { 2, 8, 32, 128, 0, };
>>> +
>>> +struct atmel_tcb_info {
>>> +	int bits;
>>> +};
>>> +
>>> +static const struct atmel_tcb_info atmel_tcb_infos[] = {
>>> +	{ .bits = 16 },
>>> +	{ .bits = 32 },
>>> +};
>>
>> Structuring the code with structure is a good practice. However, this is
>> too much :)
>>
> 
> I was going to add the divisor there but as AVR32 is gone, this is
> indeed unnecessary.
> 
>>> +static const struct of_device_id atmel_tcb_dt_ids[] = {
>>> +	{
>>> +		.compatible = "atmel,at91rm9200-tcb",
>>> +		.data = &atmel_tcb_infos[0],
>>
>> 		.data = (void *)16;
>>
>>> +	}, {
>>> +		.compatible = "atmel,at91sam9x5-tcb",
>>> +		.data = &atmel_tcb_infos[1],
>>> +	}, {
>>> +		/* sentinel */
>>> +	}
>>> +};
>>> +
>>
>>
>>
>>> +#endif /* __SOC_ATMEL_TCB_H */
>>>
>>
>>
>> -- 
>>  <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
>>
>> Follow Linaro:  <http://www.facebook.com/pages/Linaro> Facebook |
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>>
> 


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