iio:adc:at91-sama5d2: cleanup mode register use

Do not erase previous configuration of the mode register when setting
the sampling frequency.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index 5bc038f2360967a14c26ade825d1a565a9ebf16e..01ba1068613e0f7245b83e4e822e5cb1a894f37e 100644 (file)
--- a/drivers/iio/adc/at91-sama5d2_adc.c
+++ b/drivers/iio/adc/at91-sama5d2_adc.c
@@ -66,8 +66,10 @@
 #define        AT91_SAMA5D2_MR_PRESCAL(v)      ((v) << AT91_SAMA5D2_MR_PRESCAL_OFFSET)
 #define        AT91_SAMA5D2_MR_PRESCAL_OFFSET  8
 #define        AT91_SAMA5D2_MR_PRESCAL_MAX     0xff
+#define AT91_SAMA5D2_MR_PRESCAL_MASK   GENMASK(15, 8)
 /* Startup Time */
 #define        AT91_SAMA5D2_MR_STARTUP(v)      ((v) << 16)
+#define AT91_SAMA5D2_MR_STARTUP_MASK   GENMASK(19, 16)
 /* Analog Change */
 #define        AT91_SAMA5D2_MR_ANACH           BIT(23)
 /* Tracking Time */
@@ -226,7 +228,7 @@ static unsigned at91_adc_startup_time(unsigned startup_time_min,
 static void at91_adc_setup_samp_freq(struct at91_adc_state *st, unsigned freq)
 {
        struct iio_dev *indio_dev = iio_priv_to_dev(st);
-       unsigned f_per, prescal, startup;
+       unsigned f_per, prescal, startup, mr;
 
        f_per = clk_get_rate(st->per_clk);
        prescal = (f_per / (2 * freq)) - 1;
@@ -234,10 +236,11 @@ static void at91_adc_setup_samp_freq(struct at91_adc_state *st, unsigned freq)
        startup = at91_adc_startup_time(st->soc_info.startup_time,
                                        freq / 1000);
 
-       at91_adc_writel(st, AT91_SAMA5D2_MR,
-                       AT91_SAMA5D2_MR_TRANSFER(2)
-                       | AT91_SAMA5D2_MR_STARTUP(startup)
-                       | AT91_SAMA5D2_MR_PRESCAL(prescal));
+       mr = at91_adc_readl(st, AT91_SAMA5D2_MR);
+       mr &= ~(AT91_SAMA5D2_MR_STARTUP_MASK | AT91_SAMA5D2_MR_PRESCAL_MASK);
+       mr |= AT91_SAMA5D2_MR_STARTUP(startup);
+       mr |= AT91_SAMA5D2_MR_PRESCAL(prescal);
+       at91_adc_writel(st, AT91_SAMA5D2_MR, mr);
 
        dev_dbg(&indio_dev->dev, "freq: %u, startup: %u, prescal: %u\n",
                freq, startup, prescal);
@@ -444,6 +447,8 @@ static int at91_adc_probe(struct platform_device *pdev)
 
        at91_adc_writel(st, AT91_SAMA5D2_CR, AT91_SAMA5D2_CR_SWRST);
        at91_adc_writel(st, AT91_SAMA5D2_IDR, 0xffffffff);
+       /* Transfer field must be set to 2 according to the datasheet. */
+       at91_adc_writel(st, AT91_SAMA5D2_MR, AT91_SAMA5D2_MR_TRANSFER(2));
 
        at91_adc_setup_samp_freq(st, st->soc_info.min_sample_rate);