| Message ID | 1376219071-29946-4-git-send-email-josh.wu@atmel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Josh, On Sun, Aug 11, 2013 at 07:04:30PM +0800, Josh Wu wrote: > Since in at91sam9x5, sama5d3x chip. the start up time calucation is > changed. This patch can choose different start up time calculation > formula for different chips. > > Signed-off-by: Josh Wu <josh.wu@atmel.com> > --- > v1 --> v2: > add a new variable for different start_time calculation. > > drivers/iio/adc/at91_adc.c | 42 +++++++++++++++++++++++++++++++++++------- > 1 file changed, 35 insertions(+), 7 deletions(-) > > diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c > index b41eb60..9b0ffff 100644 > --- a/drivers/iio/adc/at91_adc.c > +++ b/drivers/iio/adc/at91_adc.c > @@ -40,6 +40,7 @@ > (writel_relaxed(val, st->reg_base + reg)) > > struct at91_adc_caps { > + bool start_time_use_lookup_tab; > u32 mr_prescal_mask; > u32 mr_startup_mask; > }; > @@ -700,13 +701,39 @@ static int at91_adc_probe(struct platform_device *pdev) > goto error_disable_adc_clk; > } > > - /* > - * Number of ticks needed to cover the startup time of the ADC as > - * defined in the electrical characteristics of the board, divided by 8. > - * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock > - */ > - ticks = round_up((st->startup_time * adc_clk_khz / > - 1000) - 1, 8) / 8; > + if (!st->caps->start_time_use_lookup_tab) { > + /* > + * Number of ticks needed to cover the startup time of the ADC > + * as defined in the electrical characteristics of the board, > + * divided by 8. The formula thus is : > + * Startup Time = (ticks + 1) * 8 / ADC Clock > + */ > + ticks = round_up((st->startup_time * adc_clk_khz / > + 1000) - 1, 8) / 8; > + } else { > + /* > + * For sama5d3x and at91sam9x5, the formula changes to: > + * Startup Time = <lookup_table_value> / ADC Clock > + */ > + const int startup_lookup[] = { > + 0 , 8 , 16 , 24 , > + 64 , 80 , 96 , 112, > + 512, 576, 640, 704, > + 768, 832, 896, 960 > + }; > + > + int i, size = ARRAY_SIZE(startup_lookup); > + ticks = st->startup_time * adc_clk_khz / 1000; > + for (i = 0; i < size; i++) > + if (ticks < startup_lookup[i]) > + break; > + > + ticks = i; > + if (ticks == size) > + /* Reach the end of lookup table */ > + ticks = size - 1; > + } > + Maybe just declaring two different functions here to calculate the number of ticks, and just holding the function pointer in your structure would make things more readable and future-proof? Maxime
Hi, Maxime On 8/16/2013 3:27 AM, Maxime Ripard wrote: > Hi Josh, > > On Sun, Aug 11, 2013 at 07:04:30PM +0800, Josh Wu wrote: >> Since in at91sam9x5, sama5d3x chip. the start up time calucation is >> changed. This patch can choose different start up time calculation >> formula for different chips. >> >> Signed-off-by: Josh Wu <josh.wu@atmel.com> >> --- >> v1 --> v2: >> add a new variable for different start_time calculation. >> >> drivers/iio/adc/at91_adc.c | 42 +++++++++++++++++++++++++++++++++++------- >> 1 file changed, 35 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c >> index b41eb60..9b0ffff 100644 >> --- a/drivers/iio/adc/at91_adc.c >> +++ b/drivers/iio/adc/at91_adc.c >> @@ -40,6 +40,7 @@ >> (writel_relaxed(val, st->reg_base + reg)) >> >> struct at91_adc_caps { >> + bool start_time_use_lookup_tab; >> u32 mr_prescal_mask; >> u32 mr_startup_mask; >> }; >> @@ -700,13 +701,39 @@ static int at91_adc_probe(struct platform_device *pdev) >> goto error_disable_adc_clk; >> } >> >> - /* >> - * Number of ticks needed to cover the startup time of the ADC as >> - * defined in the electrical characteristics of the board, divided by 8. >> - * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock >> - */ >> - ticks = round_up((st->startup_time * adc_clk_khz / >> - 1000) - 1, 8) / 8; >> + if (!st->caps->start_time_use_lookup_tab) { >> + /* >> + * Number of ticks needed to cover the startup time of the ADC >> + * as defined in the electrical characteristics of the board, >> + * divided by 8. The formula thus is : >> + * Startup Time = (ticks + 1) * 8 / ADC Clock >> + */ >> + ticks = round_up((st->startup_time * adc_clk_khz / >> + 1000) - 1, 8) / 8; >> + } else { >> + /* >> + * For sama5d3x and at91sam9x5, the formula changes to: >> + * Startup Time = <lookup_table_value> / ADC Clock >> + */ >> + const int startup_lookup[] = { >> + 0 , 8 , 16 , 24 , >> + 64 , 80 , 96 , 112, >> + 512, 576, 640, 704, >> + 768, 832, 896, 960 >> + }; >> + >> + int i, size = ARRAY_SIZE(startup_lookup); >> + ticks = st->startup_time * adc_clk_khz / 1000; >> + for (i = 0; i < size; i++) >> + if (ticks < startup_lookup[i]) >> + break; >> + >> + ticks = i; >> + if (ticks == size) >> + /* Reach the end of lookup table */ >> + ticks = size - 1; >> + } >> + > Maybe just declaring two different functions here to calculate the > number of ticks, and just holding the function pointer in your structure > would make things more readable and future-proof? I'll do this in next version. thanks. > > Maxime > Best Regards, Josh Wu
diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c index b41eb60..9b0ffff 100644 --- a/drivers/iio/adc/at91_adc.c +++ b/drivers/iio/adc/at91_adc.c @@ -40,6 +40,7 @@ (writel_relaxed(val, st->reg_base + reg)) struct at91_adc_caps { + bool start_time_use_lookup_tab; u32 mr_prescal_mask; u32 mr_startup_mask; }; @@ -700,13 +701,39 @@ static int at91_adc_probe(struct platform_device *pdev) goto error_disable_adc_clk; } - /* - * Number of ticks needed to cover the startup time of the ADC as - * defined in the electrical characteristics of the board, divided by 8. - * The formula thus is : Startup Time = (ticks + 1) * 8 / ADC Clock - */ - ticks = round_up((st->startup_time * adc_clk_khz / - 1000) - 1, 8) / 8; + if (!st->caps->start_time_use_lookup_tab) { + /* + * Number of ticks needed to cover the startup time of the ADC + * as defined in the electrical characteristics of the board, + * divided by 8. The formula thus is : + * Startup Time = (ticks + 1) * 8 / ADC Clock + */ + ticks = round_up((st->startup_time * adc_clk_khz / + 1000) - 1, 8) / 8; + } else { + /* + * For sama5d3x and at91sam9x5, the formula changes to: + * Startup Time = <lookup_table_value> / ADC Clock + */ + const int startup_lookup[] = { + 0 , 8 , 16 , 24 , + 64 , 80 , 96 , 112, + 512, 576, 640, 704, + 768, 832, 896, 960 + }; + + int i, size = ARRAY_SIZE(startup_lookup); + ticks = st->startup_time * adc_clk_khz / 1000; + for (i = 0; i < size; i++) + if (ticks < startup_lookup[i]) + break; + + ticks = i; + if (ticks == size) + /* Reach the end of lookup table */ + ticks = size - 1; + } + /* * a minimal Sample and Hold Time is necessary for the ADC to guarantee * the best converted final value between two channels selection @@ -798,6 +825,7 @@ static struct at91_adc_caps at91sam9g45_caps = { }; static struct at91_adc_caps at91sam9x5_caps = { + .start_time_use_lookup_tab = true, .mr_prescal_mask = AT91_ADC_PRESCAL_9G45, /* same as 9G45 */ .mr_startup_mask = AT91_ADC_STARTUP_9X5, };
Since in at91sam9x5, sama5d3x chip. the start up time calucation is changed. This patch can choose different start up time calculation formula for different chips. Signed-off-by: Josh Wu <josh.wu@atmel.com> --- v1 --> v2: add a new variable for different start_time calculation. drivers/iio/adc/at91_adc.c | 42 +++++++++++++++++++++++++++++++++++------- 1 file changed, 35 insertions(+), 7 deletions(-)