diff options
Diffstat (limited to 'drivers/iio/imu/adis16475.c')
| -rw-r--r-- | drivers/iio/imu/adis16475.c | 118 |
1 files changed, 90 insertions, 28 deletions
diff --git a/drivers/iio/imu/adis16475.c b/drivers/iio/imu/adis16475.c index 197d48240991..8f6bea4b6608 100644 --- a/drivers/iio/imu/adis16475.c +++ b/drivers/iio/imu/adis16475.c @@ -17,6 +17,8 @@ #include <linux/iio/sysfs.h> #include <linux/iio/trigger_consumer.h> #include <linux/irq.h> +#include <linux/lcm.h> +#include <linux/math.h> #include <linux/module.h> #include <linux/mod_devicetable.h> #include <linux/property.h> @@ -101,6 +103,7 @@ struct adis16475 { u32 clk_freq; bool burst32; unsigned long lsb_flag; + u16 sync_mode; /* Alignment needed for the timestamp */ __be16 data[ADIS16475_MAX_SCAN_DATA] __aligned(8); }; @@ -117,6 +120,11 @@ enum { ADIS16475_SCAN_CRC_FAILURE, }; +static bool low_rate_allow; +module_param(low_rate_allow, bool, 0444); +MODULE_PARM_DESC(low_rate_allow, + "Allow IMU rates below the minimum advisable when external clk is used in SCALED mode (default: N)"); + #ifdef CONFIG_DEBUG_FS static ssize_t adis16475_show_firmware_revision(struct file *file, char __user *userbuf, @@ -253,25 +261,92 @@ static int adis16475_get_freq(struct adis16475 *st, u32 *freq) { int ret; u16 dec; + u32 sample_rate = st->clk_freq; + + adis_dev_lock(&st->adis); + + if (st->sync_mode == ADIS16475_SYNC_SCALED) { + u16 sync_scale; + + ret = __adis_read_reg_16(&st->adis, ADIS16475_REG_UP_SCALE, &sync_scale); + if (ret) + goto error; + + sample_rate = st->clk_freq * sync_scale; + } - ret = adis_read_reg_16(&st->adis, ADIS16475_REG_DEC_RATE, &dec); + ret = __adis_read_reg_16(&st->adis, ADIS16475_REG_DEC_RATE, &dec); if (ret) - return -EINVAL; + goto error; - *freq = DIV_ROUND_CLOSEST(st->clk_freq, dec + 1); + adis_dev_unlock(&st->adis); + + *freq = DIV_ROUND_CLOSEST(sample_rate, dec + 1); return 0; +error: + adis_dev_unlock(&st->adis); + return ret; } static int adis16475_set_freq(struct adis16475 *st, const u32 freq) { u16 dec; int ret; + u32 sample_rate = st->clk_freq; if (!freq) return -EINVAL; - dec = DIV_ROUND_CLOSEST(st->clk_freq, freq); + adis_dev_lock(&st->adis); + /* + * When using sync scaled mode, the input clock needs to be scaled so that we have + * an IMU sample rate between (optimally) 1900 and 2100. After this, we can use the + * decimation filter to lower the sampling rate in order to get what the user wants. + * Optimally, the user sample rate is a multiple of both the IMU sample rate and + * the input clock. Hence, calculating the sync_scale dynamically gives us better + * chances of achieving a perfect/integer value for DEC_RATE. The math here is: + * 1. lcm of the input clock and the desired output rate. + * 2. get the highest multiple of the previous result lower than the adis max rate. + * 3. The last result becomes the IMU sample rate. Use that to calculate SYNC_SCALE + * and DEC_RATE (to get the user output rate) + */ + if (st->sync_mode == ADIS16475_SYNC_SCALED) { + unsigned long scaled_rate = lcm(st->clk_freq, freq); + int sync_scale; + + /* + * If lcm is bigger than the IMU maximum sampling rate there's no perfect + * solution. In this case, we get the highest multiple of the input clock + * lower than the IMU max sample rate. + */ + if (scaled_rate > 2100000) + scaled_rate = 2100000 / st->clk_freq * st->clk_freq; + else + scaled_rate = 2100000 / scaled_rate * scaled_rate; + + /* + * This is not an hard requirement but it's not advised to run the IMU + * with a sample rate lower than 4000Hz due to possible undersampling + * issues. However, there are users that might really want to take the risk. + * Hence, we provide a module parameter for them. If set, we allow sample + * rates lower than 4KHz. By default, we won't allow this and we just roundup + * the rate to the next multiple of the input clock bigger than 4KHz. This + * is done like this as in some cases (when DEC_RATE is 0) might give + * us the closest value to the one desired by the user... + */ + if (scaled_rate < 1900000 && !low_rate_allow) + scaled_rate = roundup(1900000, st->clk_freq); + + sync_scale = scaled_rate / st->clk_freq; + ret = __adis_write_reg_16(&st->adis, ADIS16475_REG_UP_SCALE, sync_scale); + if (ret) + goto error; + + sample_rate = scaled_rate; + } + + dec = DIV_ROUND_CLOSEST(sample_rate, freq); if (dec) dec--; @@ -281,7 +356,7 @@ static int adis16475_set_freq(struct adis16475 *st, const u32 freq) ret = adis_write_reg_16(&st->adis, ADIS16475_REG_DEC_RATE, dec); if (ret) - return ret; + goto error; /* * If decimation is used, then gyro and accel data will have meaningful @@ -290,6 +365,9 @@ static int adis16475_set_freq(struct adis16475 *st, const u32 freq) assign_bit(ADIS16475_LSB_DEC_MASK, &st->lsb_flag, dec); return 0; +error: + adis_dev_unlock(&st->adis); + return ret; } /* The values are approximated. */ @@ -1085,6 +1163,7 @@ static int adis16475_config_sync_mode(struct adis16475 *st) } sync = &st->info->sync[sync_mode]; + st->sync_mode = sync->sync_mode; /* All the other modes require external input signal */ if (sync->sync_mode != ADIS16475_SYNC_OUTPUT) { @@ -1112,37 +1191,20 @@ static int adis16475_config_sync_mode(struct adis16475 *st) if (sync->sync_mode == ADIS16475_SYNC_SCALED) { u16 up_scale; - u32 scaled_out_freq = 0; + /* - * If we are in scaled mode, we must have an up_scale. - * In scaled mode the allowable input clock range is - * 1 Hz to 128 Hz, and the allowable output range is - * 1900 to 2100 Hz. Hence, a scale must be given to - * get the allowable output. + * In sync scaled mode, the IMU sample rate is the clk_freq * sync_scale. + * Hence, default the IMU sample rate to the highest multiple of the input + * clock lower than the IMU max sample rate. The optimal range is + * 1900-2100 sps... */ - ret = device_property_read_u32(dev, - "adi,scaled-output-hz", - &scaled_out_freq); - if (ret) { - dev_err(dev, "adi,scaled-output-hz must be given when in scaled sync mode"); - return -EINVAL; - } else if (scaled_out_freq < 1900 || - scaled_out_freq > 2100) { - dev_err(dev, "Invalid value: %u for adi,scaled-output-hz", - scaled_out_freq); - return -EINVAL; - } - - up_scale = DIV_ROUND_CLOSEST(scaled_out_freq, - st->clk_freq); + up_scale = 2100 / st->clk_freq; ret = __adis_write_reg_16(&st->adis, ADIS16475_REG_UP_SCALE, up_scale); if (ret) return ret; - - st->clk_freq = scaled_out_freq; } st->clk_freq *= 1000; |