diff options
| -rw-r--r-- | drivers/iio/adc/xilinx-xadc-core.c | 78 |
1 files changed, 60 insertions, 18 deletions
diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-xadc-core.c index 1aeaeafce589..6fd06e4eff73 100644 --- a/drivers/iio/adc/xilinx-xadc-core.c +++ b/drivers/iio/adc/xilinx-xadc-core.c @@ -102,6 +102,16 @@ static const unsigned int XADC_ZYNQ_UNMASK_TIMEOUT = 500; #define XADC_FLAGS_BUFFERED BIT(0) +/* + * The XADC hardware supports a samplerate of up to 1MSPS. Unfortunately it does + * not have a hardware FIFO. Which means an interrupt is generated for each + * conversion sequence. At 1MSPS sample rate the CPU in ZYNQ7000 is completely + * overloaded by the interrupts that it soft-lockups. For this reason the driver + * limits the maximum samplerate 150kSPS. At this rate the CPU is fairly busy, + * but still responsive. + */ +#define XADC_MAX_SAMPLERATE 150000 + static void xadc_write_reg(struct xadc *xadc, unsigned int reg, uint32_t val) { @@ -834,11 +844,27 @@ static const struct iio_buffer_setup_ops xadc_buffer_ops = { .postdisable = &xadc_postdisable, }; +static int xadc_read_samplerate(struct xadc *xadc) +{ + unsigned int div; + uint16_t val16; + int ret; + + ret = xadc_read_adc_reg(xadc, XADC_REG_CONF2, &val16); + if (ret) + return ret; + + div = (val16 & XADC_CONF2_DIV_MASK) >> XADC_CONF2_DIV_OFFSET; + if (div < 2) + div = 2; + + return xadc_get_dclk_rate(xadc) / div / 26; +} + static int xadc_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan, int *val, int *val2, long info) { struct xadc *xadc = iio_priv(indio_dev); - unsigned int div; uint16_t val16; int ret; @@ -891,41 +917,31 @@ static int xadc_read_raw(struct iio_dev *indio_dev, *val = -((273150 << 12) / 503975); return IIO_VAL_INT; case IIO_CHAN_INFO_SAMP_FREQ: - ret = xadc_read_adc_reg(xadc, XADC_REG_CONF2, &val16); - if (ret) + ret = xadc_read_samplerate(xadc); + if (ret < 0) return ret; - div = (val16 & XADC_CONF2_DIV_MASK) >> XADC_CONF2_DIV_OFFSET; - if (div < 2) - div = 2; - - *val = xadc_get_dclk_rate(xadc) / div / 26; - + *val = ret; return IIO_VAL_INT; default: return -EINVAL; } } -static int xadc_write_raw(struct iio_dev *indio_dev, - struct iio_chan_spec const *chan, int val, int val2, long info) +static int xadc_write_samplerate(struct xadc *xadc, int val) { - struct xadc *xadc = iio_priv(indio_dev); unsigned long clk_rate = xadc_get_dclk_rate(xadc); unsigned int div; if (!clk_rate) return -EINVAL; - if (info != IIO_CHAN_INFO_SAMP_FREQ) - return -EINVAL; - if (val <= 0) return -EINVAL; /* Max. 150 kSPS */ - if (val > 150000) - val = 150000; + if (val > XADC_MAX_SAMPLERATE) + val = XADC_MAX_SAMPLERATE; val *= 26; @@ -938,7 +954,7 @@ static int xadc_write_raw(struct iio_dev *indio_dev, * limit. */ div = clk_rate / val; - if (clk_rate / div / 26 > 150000) + if (clk_rate / div / 26 > XADC_MAX_SAMPLERATE) div++; if (div < 2) div = 2; @@ -949,6 +965,17 @@ static int xadc_write_raw(struct iio_dev *indio_dev, div << XADC_CONF2_DIV_OFFSET); } +static int xadc_write_raw(struct iio_dev *indio_dev, + struct iio_chan_spec const *chan, int val, int val2, long info) +{ + struct xadc *xadc = iio_priv(indio_dev); + + if (info != IIO_CHAN_INFO_SAMP_FREQ) + return -EINVAL; + + return xadc_write_samplerate(xadc, val); +} + static const struct iio_event_spec xadc_temp_events[] = { { .type = IIO_EV_TYPE_THRESH, @@ -1234,6 +1261,21 @@ static int xadc_probe(struct platform_device *pdev) if (ret) goto err_free_samplerate_trigger; + /* + * Make sure not to exceed the maximum samplerate since otherwise the + * resulting interrupt storm will soft-lock the system. + */ + if (xadc->ops->flags & XADC_FLAGS_BUFFERED) { + ret = xadc_read_samplerate(xadc); + if (ret < 0) + goto err_free_samplerate_trigger; + if (ret > XADC_MAX_SAMPLERATE) { + ret = xadc_write_samplerate(xadc, XADC_MAX_SAMPLERATE); + if (ret < 0) + goto err_free_samplerate_trigger; + } + } + ret = request_irq(xadc->irq, xadc->ops->interrupt_handler, 0, dev_name(&pdev->dev), indio_dev); if (ret) |