[PATCH 2/2] ARM: plat-mxc: Fix pwm frequency

[PATCH 2/2] ARM: plat-mxc: Fix pwm frequency

[Sascha Hauer]

On Thu, Jun 30, 2011 at 06:50:35PM -0700, Troy Kisky wrote:
> The PWMPR register is number of clocks + 2, so include
> a -2 when setting the register. There is currently no rounding
> up, so this may give a higher frequency than requested.

Have you checked this applies to mx2/3 aswell?

Sascha

> 
> Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
> ---
>  arch/arm/plat-mxc/pwm.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/arm/plat-mxc/pwm.c b/arch/arm/plat-mxc/pwm.c
> index 73f17b2..844415e 100644
> --- a/arch/arm/plat-mxc/pwm.c
> +++ b/arch/arm/plat-mxc/pwm.c
> @@ -76,7 +76,13 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
>  		duty_cycles = c;
>  
>  		writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
> -		writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
> +		if (period_cycles < 2)
> +			period_cycles = 2;
> +		/*
> +		 * manual says - "A value of zero in the PWMPR will result in
> +		 * a period of two clock cycles for the output signal.
> +		 */
> +		writel(period_cycles - 2, pwm->mmio_base + MX3_PWMPR);
>  
>  		cr = MX3_PWMCR_PRESCALER(prescale) | MX3_PWMCR_EN;
>  
> -- 
> 1.7.0.4
> 
> 

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[PATCH 2/2] ARM: plat-mxc: Fix pwm frequency

[Troy Kisky]

On 7/1/2011 1:03 AM, Sascha Hauer wrote:
> On Thu, Jun 30, 2011 at 06:50:35PM -0700, Troy Kisky wrote:
>> The PWMPR register is number of clocks + 2, so include
>> a -2 when setting the register. There is currently no rounding
>> up, so this may give a higher frequency than requested.
> 
> Have you checked this applies to mx2/3 aswell?
> 
> Sascha
> 
>>
>> Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
>> ---
>>  arch/arm/plat-mxc/pwm.c |    8 +++++++-
>>  1 files changed, 7 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/arm/plat-mxc/pwm.c b/arch/arm/plat-mxc/pwm.c
>> index 73f17b2..844415e 100644
>> --- a/arch/arm/plat-mxc/pwm.c
>> +++ b/arch/arm/plat-mxc/pwm.c
>> @@ -76,7 +76,13 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
>>  		duty_cycles = c;
>>  
>>  		writel(duty_cycles, pwm->mmio_base + MX3_PWMSAR);
>> -		writel(period_cycles, pwm->mmio_base + MX3_PWMPR);
>> +		if (period_cycles < 2)
>> +			period_cycles = 2;
>> +		/*
>> +		 * manual says - "A value of zero in the PWMPR will result in
>> +		 * a period of two clock cycles for the output signal.
>> +		 */
>> +		writel(period_cycles - 2, pwm->mmio_base + MX3_PWMPR);
>>  
>>  		cr = MX3_PWMCR_PRESCALER(prescale) | MX3_PWMCR_EN;
>>  
>> -- 
>> 1.7.0.4
>>
>>
> 
I just checked. It applies to mx27, mx31, mx25, mx51, mx53.

Thanks for the reminder.

Troy