Re: [PATCH 05/15] ARM: at91: sam9m10g45ek: Add touchscreen support through at91_adc

From: Alexandre Belloni
Date: Sun Mar 16 2014 - 16:01:21 EST


On 16/03/2014 at 18:18:41 +0000, Jonathan Cameron wrote :
> On 05/03/14 17:35, Alexandre Belloni wrote:
> >at91_adc now supports reading a touchscreen for ADCs without a TSMR register.
> >Enable touchscreen support through at91_adc. This allows to use both a
> >touchscreen and the remaining ADC channel at the same time.
> >
> >Also, lower the clock for the ADC as it allows to have more stable reads and
> >this is the speed used by atmel_tsadcc.
> Are there any side effects on the adc read if that functionality was previously
> being used? I doubt it matters, but probably wants to be mentioned here if there
> is.

Hum, it lowers the throughput rate but I really doubt anyone is trying
to achieve 440000 samples per second under linux ;) At that frequency,
we are still able to achieve 12958 samples per second so I guess this is
fine as from my experience, the CPU can't really keep up when reading
500 samples per seconds. I will include that in the commit log.

> >Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx>
> >---
> > arch/arm/mach-at91/at91sam9g45.c | 2 +-
> > arch/arm/mach-at91/board-sam9m10g45ek.c | 1 +
> > 2 files changed, 2 insertions(+), 1 deletion(-)
> >
> >diff --git a/arch/arm/mach-at91/at91sam9g45.c b/arch/arm/mach-at91/at91sam9g45.c
> >index 2f455ce35268..3c519a7a938f 100644
> >--- a/arch/arm/mach-at91/at91sam9g45.c
> >+++ b/arch/arm/mach-at91/at91sam9g45.c
> >@@ -181,7 +181,7 @@ static struct clk vdec_clk = {
> > static struct clk adc_op_clk = {
> > .name = "adc_op_clk",
> > .type = CLK_TYPE_PERIPHERAL,
> >- .rate_hz = 13200000,
> >+ .rate_hz = 300000,
> > };
> >
> > /* AES/TDES/SHA clock - Only for sam9m11/sam9g56 */
> >diff --git a/arch/arm/mach-at91/board-sam9m10g45ek.c b/arch/arm/mach-at91/board-sam9m10g45ek.c
> >index ef39078c8ce2..4d775b796ce4 100644
> >--- a/arch/arm/mach-at91/board-sam9m10g45ek.c
> >+++ b/arch/arm/mach-at91/board-sam9m10g45ek.c
> >@@ -315,6 +315,7 @@ static struct at91_adc_data ek_adc_data = {
> > .channels_used = BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5) | BIT(6) | BIT(7),
> > .use_external_triggers = true,
> > .vref = 3300,
> >+ .touchscreen_type = ATMEL_ADC_TOUCHSCREEN_4WIRE,
> > };
> >
> > /*
> >
>

--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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