linux-kernel - Re: [PATCH v2 1/3] mmc: sdhci: introduce sdhci_compute_clock

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Date:	Thu, 7 Apr 2016 10:47:38 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Ludovic Desroches <ludovic.desroches@...el.com>
Cc:	ulf.hansson@...aro.org, linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org, nicolas.ferre@...el.com
Subject: Re: [PATCH v2 1/3] mmc: sdhci: introduce sdhci_compute_clock_config

On 06/04/16 18:04, Ludovic Desroches wrote:
> On Wed, Apr 06, 2016 at 03:37:28PM +0300, Adrian Hunter wrote:
>> On 04/04/16 18:27, Ludovic Desroches wrote:
>>> In order to remove the SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST and to
>>> reduce code duplication, put the code relative to the SD clock
>>> configuration in a function which can be used by hosts for the
>>> implementation of the set_clock() callback.
>>>
>>> Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
>>> ---
>>>  drivers/mmc/host/sdhci.c | 33 ++++++++++++++++++++++-----------
>>>  drivers/mmc/host/sdhci.h |  1 +
>>>  2 files changed, 23 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 6bd3d17..2c3dede 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -1091,23 +1091,13 @@ static u16 sdhci_get_preset_value(struct sdhci_host *host)
>>>  	return preset;
>>>  }
>>>  
>>> -void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>>> +u16 sdhci_compute_clock_config(struct sdhci_host *host, unsigned int clock)
>>
>> The function name 'sdhci_compute_clock_config' seems a bit long.  How about
>> just sdhci_calc_clk.
> 
> Ok.
> 
>>
>> Also it needs to calculate 'actual_clock' too, so it needs to do that and
>> return the value.
>>
> 
> actual_clock is updated at the end of the function.
> 
> Which value has to be returned? actual_clock or clock configuration?

The function doesn't update the clock, so I don't think it should update
actual_clock either, just return it. i.e.

u16 sdhci_calc_clk(struct sdhci_host *host, unsigned int clock, unsigned int *actual_clock)
{
	...
	if (real_div)
		*actual_clock = (host->max_clk * clk_mul) / real_div;
	...
	return clk;
}

then

	clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);



> 
> Regards
> 
> Ludovic
> 
>>>  {
>>>  	int div = 0; /* Initialized for compiler warning */
>>>  	int real_div = div, clk_mul = 1;
>>>  	u16 clk = 0;
>>> -	unsigned long timeout;
>>>  	bool switch_base_clk = false;
>>>  
>>> -	host->mmc->actual_clock = 0;
>>> -
>>> -	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>>> -	if (host->quirks2 & SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST)
>>> -		mdelay(1);
>>> -
>>> -	if (clock == 0)
>>> -		return;
>>> -
>>>  	if (host->version >= SDHCI_SPEC_300) {
>>>  		if (host->preset_enabled) {
>>>  			u16 pre_val;
>>> @@ -1188,6 +1178,27 @@ clock_set:
>>>  	clk |= (div & SDHCI_DIV_MASK) << SDHCI_DIVIDER_SHIFT;
>>>  	clk |= ((div & SDHCI_DIV_HI_MASK) >> SDHCI_DIV_MASK_LEN)
>>>  		<< SDHCI_DIVIDER_HI_SHIFT;
>>> +
>>> +	return clk;
>>> +}
>>> +EXPORT_SYMBOL_GPL(sdhci_compute_clock_config);
>>> +
>>> +void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>>> +{
>>> +	u16 clk;
>>> +	unsigned long timeout;
>>> +
>>> +	host->mmc->actual_clock = 0;
>>> +
>>> +	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>>> +	if (host->quirks2 & SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST)
>>> +		mdelay(1);
>>> +
>>> +	if (clock == 0)
>>> +		return;
>>> +
>>> +	clk = sdhci_compute_clock_config(host, clock);
>>> +
>>>  	clk |= SDHCI_CLOCK_INT_EN;
>>>  	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
>>>  
>>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
>>> index 0f39f4f..23ddd6e 100644
>>> --- a/drivers/mmc/host/sdhci.h
>>> +++ b/drivers/mmc/host/sdhci.h
>>> @@ -661,6 +661,7 @@ static inline bool sdhci_sdio_irq_enabled(struct sdhci_host *host)
>>>  	return !!(host->flags & SDHCI_SDIO_IRQ_ENABLED);
>>>  }
>>>  
>>> +u16 sdhci_compute_clock_config(struct sdhci_host *host, unsigned int clock);
>>>  void sdhci_set_clock(struct sdhci_host *host, unsigned int clock);
>>>  void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
>>>  		     unsigned short vdd);
>>>
>>
>