[PATCH v1] meson saradc: fix clock divider mask length
George Stark
gnstark at sberdevices.ru
Thu Jun 1 13:52:17 PDT 2023
On 5/29/23 23:41, Martin Blumenstingl wrote:
> Hi George,
>
> On Mon, May 22, 2023 at 5:47 PM Старк Георгий Николаевич
> <GNStark at sberdevices.ru> wrote:
>> Hello Martin
>>
>> Actually you were right that my patch affects only meson8 family not the all new ones, my bad.
>> It's clear from the driver code meson_saradc.c and dts files.
>> I've made an experiment on a113l soc - changingclock_rate inmeson_sar_adc_param and measuring adc channel many times
>> and with low clockfrequency (priv->adc_clk) time of measurementis high
>> and vice versa. ADC_CLK_DIV field in SAR_ADC_REG3 is always zero.
> Thanks for sharing your findings!
>
>> I need to get s805 (meson8) board for example and made experiment on it.
> If you don't find any Meson8 (S802)/Meson8b (S805) or Meson8m2 (S812)
> board then please provide the code that you used for your experiment
> as a patch so I can give it a try on my Odroid-C1 (Meson8b).
>
>
> Best regards,
> Martin
>
Hello Martin
Here the test I promised:
Question: what's the real size of clock divder field in SAR_ADC_REG3 register in saradc in meson8 socs?
The current kernel code says 5 bits
The datasheet says 6 bit
The parent clock of adc clock is 24Mhz
I can check it here by:
# cat /sys/kernel/debug/clk/clk_summary
xtal 4 4 1 24000000 0 0 50000 Y
c1108680.adc#adc_div 1 1 0 1142858 0 0 50000 Y
c1108680.adc#adc_en 1 1 0 1142858 0 0 50000 Y
for divider width 5bit min adc clock is 24Mhz / 32 = 750KHZ
for divider width 6bit min adc clock is 24Mhz / 64 = 375KHz
I suppose that the lower adc clock rate the higher measurement time
so I need to get measurement time at both clk freqs and the times differ so
6bit divider is really applied
I performed test at Odroid-C1, kernel 6.2-rc8
Two kernel patches must be applied:
the topic starter patch and the helper patch at the end of the letter
In the helper patch I turn on CLOCK_ALLOW_WRITE_DEBUGFS to change clock rate from she shell
and use ktime_get_raw_ts64 to measure measurement time
So the the test itself:
cat /sys/devices/platform/soc/c1100000.cbus/c1108680.adc/iio:device0/in_voltage3_raw
[ 1781.226309] ==== freq: 1142858 time 42408000
# echo 750000 > /sys/kernel/debug/clk/c1108680.adc#adc_en/clk_rate
# cat /sys/devices/platform/soc/c1100000.cbus/c1108680.adc/iio:device0/in_voltage3_raw
[ 1790.728656] ==== freq: 750000 time 49173000
# echo 375000 > /sys/kernel/debug/clk/c1108680.adc#adc_en/clk_rate
# cat /sys/devices/platform/soc/c1100000.cbus/c1108680.adc/iio:device0/in_voltage3_raw
[ 1816.955477] ==== freq: 375000 time 68245000
# cat /sys/kernel/debug/clk/clk_summary
xtal 4 4 1 24000000 0 0 50000 Y
c1108680.adc#adc_div 1 1 0 375000 0 0 50000 Y
c1108680.adc#adc_en 1 1 0 375000 0 0 50000 Y
Helper patch:
diff --git a/drivers/clk/baikal-t1/ccu-pll.c
b/drivers/clk/baikal-t1/ccu-pll.c
index 13ef28001439..226e0d46a994 100644
--- a/drivers/clk/baikal-t1/ccu-pll.c
+++ b/drivers/clk/baikal-t1/ccu-pll.c
@@ -363,7 +363,7 @@ static const struct ccu_pll_dbgfs_fld ccu_pll_flds[] = {
* therefore we don't provide any kernel config based compile time
option for
* this feature to enable.
*/
-#undef CCU_PLL_ALLOW_WRITE_DEBUGFS
+#define CCU_PLL_ALLOW_WRITE_DEBUGFS
#ifdef CCU_PLL_ALLOW_WRITE_DEBUGFS
static int ccu_pll_dbgfs_bit_set(void *priv, u64 val)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index e62552a75f08..d552acdaa7bc 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3263,7 +3263,7 @@ static int clk_dump_show(struct seq_file *s, void
*data)
}
DEFINE_SHOW_ATTRIBUTE(clk_dump);
-#undef CLOCK_ALLOW_WRITE_DEBUGFS
+#define CLOCK_ALLOW_WRITE_DEBUGFS
#ifdef CLOCK_ALLOW_WRITE_DEBUGFS
/*
* This can be dangerous, therefore don't provide any real compile time
diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
index 6959a0064551..65132d3ca46a 100644
--- a/drivers/iio/adc/meson_saradc.c
+++ b/drivers/iio/adc/meson_saradc.c
@@ -24,6 +24,8 @@
#include <linux/regulator/consumer.h>
#include <linux/mfd/syscon.h>
+#include <linux/timekeeping.h>
+
#define MESON_SAR_ADC_REG0 0x00
#define MESON_SAR_ADC_REG0_PANEL_DETECT BIT(31)
#define MESON_SAR_ADC_REG0_BUSY_MASK GENMASK(30, 28)
@@ -599,6 +601,8 @@ static int meson_sar_adc_get_sample(struct iio_dev
*indio_dev,
struct device *dev = indio_dev->dev.parent;
int ret;
+ int i;
+
if (chan->type == IIO_TEMP && !priv->temperature_sensor_calibrated)
return -ENOTSUPP;
@@ -606,16 +610,28 @@ static int meson_sar_adc_get_sample(struct iio_dev
*indio_dev,
if (ret)
return ret;
- /* clear the FIFO to make sure we're not reading old values */
- meson_sar_adc_clear_fifo(indio_dev);
- meson_sar_adc_set_averaging(indio_dev, chan, avg_mode, avg_samples);
+ struct timespec64 ts0, ts1;
+ ktime_get_raw_ts64(&ts0);
- meson_sar_adc_enable_channel(indio_dev, chan);
+ for (i = 0; i < 1000; i++) {
- meson_sar_adc_start_sample_engine(indio_dev);
- ret = meson_sar_adc_read_raw_sample(indio_dev, chan, val);
- meson_sar_adc_stop_sample_engine(indio_dev);
+ /* clear the FIFO to make sure we're not reading old
values */
+ meson_sar_adc_clear_fifo(indio_dev);
+
+ meson_sar_adc_set_averaging(indio_dev, chan, avg_mode,
avg_samples);
+
+ meson_sar_adc_enable_channel(indio_dev, chan);
+
+ meson_sar_adc_start_sample_engine(indio_dev);
+ ret = meson_sar_adc_read_raw_sample(indio_dev, chan, val);
+ meson_sar_adc_stop_sample_engine(indio_dev);
+ }
+
+ ktime_get_raw_ts64(&ts1);
+ u64 t0 = NSEC_PER_SEC * ts0.tv_sec + ts0.tv_nsec;
+ u64 t1 = NSEC_PER_SEC * ts1.tv_sec + ts1.tv_nsec;
+ printk("==== freq: %lu time %lld\n",
clk_get_rate(priv->adc_clk), t1 - t0);
meson_sar_adc_unlock(indio_dev);
Best regards
George
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