linux-kernel - Re: [PATCH] clk: at91: modify PMC peripheral clock to deal with newer register layout

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Date:	Wed, 10 Jun 2015 16:39:40 +0200
From:	Nicolas Ferre <nicolas.ferre@...el.com>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
CC:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	"Ludovic Desroches" <ludovic.desroches@...el.com>,
	Josh Wu <josh.wu@...el.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	"Mike Turquette" <mturquette@...aro.org>
Subject: Re: [PATCH] clk: at91: modify PMC peripheral clock to deal with newer
 register layout

Le 10/06/2015 15:55, Boris Brezillon a écrit :
> Hi Nicolas,
> 
> On Wed, 10 Jun 2015 15:42:44 +0200
> Nicolas Ferre <nicolas.ferre@...el.com> wrote:
> 
>> As some more information is added to the PCR register, we'd better use
>> a copy of its content and modify just the peripheral-related bits.
>> Implement a read-modify-write for the enable() and disable() callbacks.
>>
>> Header file is also modified to have the PCR_DIV mask.
>>
>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
> 
> Apart from the below comment you can add my:
> 
> Acked-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> 
>> ---
>>  drivers/clk/at91/clk-peripheral.c | 19 +++++++++++++------
>>  include/linux/clk/at91_pmc.h      |  3 ++-
>>  2 files changed, 15 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/clk/at91/clk-peripheral.c b/drivers/clk/at91/clk-peripheral.c
>> index 597fed423d7d..37e2fea14890 100644
>> --- a/drivers/clk/at91/clk-peripheral.c
>> +++ b/drivers/clk/at91/clk-peripheral.c
>> @@ -161,14 +161,17 @@ static int clk_sam9x5_peripheral_enable(struct clk_hw *hw)
>>  {
>>  	struct clk_sam9x5_peripheral *periph = to_clk_sam9x5_peripheral(hw);
>>  	struct at91_pmc *pmc = periph->pmc;
>> +	u32 tmp;
>>  
>>  	if (periph->id < PERIPHERAL_ID_MIN)
>>  		return 0;
>>  
>> -	pmc_write(pmc, AT91_PMC_PCR, (periph->id & AT91_PMC_PCR_PID) |
>> -				     AT91_PMC_PCR_CMD |
>> -				     AT91_PMC_PCR_DIV(periph->div) |
>> -				     AT91_PMC_PCR_EN);
>> +	pmc_lock(pmc);
>> +	pmc_write(pmc, AT91_PMC_PCR, (periph->id & AT91_PMC_PCR_PID));
>> +	tmp = pmc_read(pmc, AT91_PMC_PCR) & ~AT91_PMC_PCR_P_DIV;
>> +	pmc_write(pmc, AT91_PMC_PCR, tmp | AT91_PMC_PCR_PDIV(periph->div)
>> +					 | AT91_PMC_PCR_EN);
>> +	pmc_unlock(pmc);
>>  	return 0;
>>  }
>>  
>> @@ -176,12 +179,16 @@ static void clk_sam9x5_peripheral_disable(struct clk_hw *hw)
>>  {
>>  	struct clk_sam9x5_peripheral *periph = to_clk_sam9x5_peripheral(hw);
>>  	struct at91_pmc *pmc = periph->pmc;
>> +	u32 tmp;
>>  
>>  	if (periph->id < PERIPHERAL_ID_MIN)
>>  		return;
>>  
>> -	pmc_write(pmc, AT91_PMC_PCR, (periph->id & AT91_PMC_PCR_PID) |
>> -				     AT91_PMC_PCR_CMD);
>> +	pmc_lock(pmc);
>> +	pmc_write(pmc, AT91_PMC_PCR, (periph->id & AT91_PMC_PCR_PID));
>> +	tmp = pmc_read(pmc, AT91_PMC_PCR) & ~AT91_PMC_PCR_EN;
>> +	pmc_write(pmc, AT91_PMC_PCR, tmp);
>> +	pmc_unlock(pmc);
>>  }
>>  
>>  static int clk_sam9x5_peripheral_is_enabled(struct clk_hw *hw)
>> diff --git a/include/linux/clk/at91_pmc.h b/include/linux/clk/at91_pmc.h
>> index 7669f7618f39..4685c3d62f94 100644
>> --- a/include/linux/clk/at91_pmc.h
>> +++ b/include/linux/clk/at91_pmc.h
>> @@ -184,7 +184,8 @@ extern void __iomem *at91_pmc_base;
>>  #define AT91_PMC_PCR		0x10c			/* Peripheral Control Register [some SAM9 and SAMA5] */
>>  #define		AT91_PMC_PCR_PID	(0x3f  <<  0)		/* Peripheral ID */
>>  #define		AT91_PMC_PCR_CMD	(0x1  <<  12)		/* Command (read=0, write=1) */
>> -#define		AT91_PMC_PCR_DIV(n)	((n)  <<  16)		/* Divisor Value */
>> +#define		AT91_PMC_PCR_P_DIV	(0x3  <<  16)		/* Divisor mask */
> 
> How about renaming this macro into AT91_PMC_PCR_PDIV_MSK ?
> I know the macro names in this file are not consistent, but maybe it's
> time to choose appropriate names for new AT91_PMC macros.

Well, this is what I tried to find: consistency ;-)
It seems that other macros are like I did for this one: the pure name of
the field for the mask and some kind of other form of the name for a
value macro or a (usually useless) list of macro-per-value things.

For this one I added a "P" for peripheral which is not in the real name
of the register field. This is to differentiate it from the upcoming
GCK_DIV field...

Bye,
-- 
Nicolas Ferre
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