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e2540da86e
linux-next/drivers/iio/adc
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David Lechner e2540da86e iio: adc: ti-ads7950: use SPI_CS_WORD to reduce CPU usage 
This changes how the SPI message for the triggered buffer is setup in
the TI ADS7950 A/DC driver. By using the SPI_CS_WORD flag, we can read
multiple samples in a single SPI transfer. If the SPI controller
supports DMA transfers, we can see a significant reduction in CPU usage.

For example, on an ARM9 system running at 456MHz reading just 4 channels
at 100Hz: before this change, top shows the CPU usage of the IRQ thread
of this driver to be ~7.7%. After this change, the CPU usage drops to
~3.8%.

The use of big-endian for the raw data was cargo culted from another
driver when this driver was originally written. It used an SPI word size
of 8 bits and big-endian byte ordering to effectively emulate 16 bit
words.

Now, in order to inject a CS toggle between each word, we need to use
the correct word size, otherwise we would get a CS toggle half way
through each word 16-bit. The SPI subsystem uses CPU byte ordering for
multi-byte words. So, the data we get back from the SPI is going to be
CPU endian now no matter what. Converting that to big endian will just
add overhead on little endian systems so we opt to change the raw data
format from big endian to CPU endian.

There is a small risk that this could break some lazy userspace programs
that use the raw data without checking the data format. We can address
this if/when it actually comes up.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
2018-09-22 10:09:47 +01:00
..
ad799x.c drivers: iio: Update MODULE AUTHOR email address 2018-08-19 17:23:39 +01:00
ad7266.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ad7291.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ad7298.c drivers: iio: Update MODULE AUTHOR email address 2018-08-19 17:23:39 +01:00
ad7476.c drivers: iio: Update MODULE AUTHOR email address 2018-08-19 17:23:39 +01:00
ad7766.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ad7791.c iio: adc: ad7791: implement IIO_CHAN_INFO_SAMP_FREQ 2018-03-17 20:47:21 +00:00
ad7793.c drivers: iio: Update MODULE AUTHOR email address 2018-08-19 17:23:39 +01:00
ad7887.c drivers: iio: Update MODULE AUTHOR email address 2018-08-19 17:23:39 +01:00
ad7923.c drivers: iio: Update MODULE AUTHOR email address 2018-08-19 17:23:39 +01:00
ad_sigma_delta.c iio: ad_sigma_delta: use unsigned long for timeout 2018-07-28 12:15:03 +01:00
aspeed_adc.c iio: adc: aspeed: Fix error handling path 2018-01-14 11:01:13 +00:00
at91_adc.c treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
at91-sama5d2_adc.c iio: adc: at91-sama5d2_adc: fix up casting in at91_adc_read_info_raw() 2018-07-23 19:18:12 +01:00
axp20x_adc.c iio: adc: axp20x_adc: remove !! in favor of ternary condition 2018-02-24 12:19:45 +00:00
axp288_adc.c iio: Add macro to populate struct iio_map array 2017-12-02 13:28:21 +00:00
bcm_iproc_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
berlin2-adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
cc10001_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
cpcap-adc.c iio: adc: cpcap: fix incorrect validation 2017-12-02 11:15:13 +00:00
da9150-gpadc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
dln2-adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
envelope-detector.c iio: envelope-detector: switch to SPDX license identifier 2018-08-20 19:27:05 +01:00
ep93xx_adc.c iio: ep93xx: remove redundant return value check of platform_get_resource() 2018-01-30 18:33:20 +00:00
exynos_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
fsl-imx25-gcq.c iio: adc: imx25-gcq: Fix module autoload 2017-01-10 19:54:56 +00:00
hi8435.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
hx711.c iio: hx711: add delay until DOUT is ready 2018-07-15 09:36:38 +01:00
imx7d_adc.c iio: adc: fix spelling mistake: "Freeacale" -> "Freescale" 2018-05-22 18:17:57 +01:00
ina2xx-adc.c iio: adc: ina2xx: avoid kthread_stop() with stale task_struct 2018-07-07 17:06:39 +01:00
Kconfig iio: adc: add support for mcp3911 2018-08-19 20:02:48 +01:00
lp8788_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
lpc18xx_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
lpc32xx_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ltc2471.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ltc2485.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ltc2497.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
Makefile iio: adc: add support for mcp3911 2018-08-19 20:02:48 +01:00
max1027.c treewide: devm_kmalloc() -> devm_kmalloc_array() 2018-06-12 16:19:22 -07:00
max1118.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
max1363.c iio: adc: max1363: merge calls to of_match_device and of_device_get_match_data 2018-07-08 10:35:17 +01:00
max9611.c iio: adc: max9611: explicitly cast gain_selectors 2018-08-19 17:48:04 +01:00
max11100.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
mcp320x.c iio: adc: mcp320x: Add support for mcp3550/1/3 2017-10-09 21:01:36 +01:00
mcp3422.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
mcp3911.c iio: adc: add support for mcp3911 2018-08-19 20:02:48 +01:00
men_z188_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
meson_saradc.c iio: adc: meson-saradc: add support for the Meson8m2 SoCs 2018-07-23 19:18:13 +01:00
mt6577_auxadc.c iio: adc: mt2712: Add compatible node for mt2712. 2017-09-24 16:45:38 +01:00
mxs-lradc-adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
nau7802.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
palmas_gpadc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
qcom-pm8xxx-xoadc.c iio: Convert to using %pOFn instead of device_node.name 2018-09-02 18:54:31 +01:00
qcom-spmi-adc5.c iio: adc: qcom-spmi-adc5: Verify channel numbers from DT 2018-09-02 18:52:04 +01:00
qcom-spmi-iadc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
qcom-spmi-vadc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
qcom-vadc-common.c iio: adc: Add QCOM SPMI PMIC5 ADC driver 2018-08-18 18:11:43 +01:00
qcom-vadc-common.h iio: adc: Add QCOM SPMI PMIC5 ADC driver 2018-08-18 18:11:43 +01:00
rcar-gyroadc.c iio: Convert to using %pOFn instead of device_node.name 2018-09-02 18:54:31 +01:00
rockchip_saradc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
sc27xx_adc.c iio: adc: sc27xx: Add ADC scale calibration 2018-09-02 09:52:55 +01:00
sd_adc_modulator.c IIO: ADC: add sigma delta modulator support 2018-01-10 10:30:09 +00:00
spear_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
stm32-adc-core.c iio: adc: stm32-adc: add support for STM32MP1 2018-05-07 18:21:00 +01:00
stm32-adc-core.h iio: stm32: Adopt SPDX identifier 2018-01-08 16:03:41 +01:00
stm32-adc.c iio: adc: stm32-adc: add support for STM32MP1 2018-05-07 18:21:00 +01:00
stm32-dfsdm-adc.c Staging/IIO patches for 4.18-rc1 2018-06-09 10:32:39 -07:00
stm32-dfsdm-core.c iio: adc: stm32-dfsdm: Add support for stm32mp1 2018-05-12 10:22:17 +01:00
stm32-dfsdm.h IIO: ADC: add stm32 DFSDM core support 2018-01-10 10:30:11 +00:00
stx104.c iio: stx104: Implement get_multiple callback 2018-03-17 16:21:27 +00:00
sun4i-gpadc-iio.c iio: adc: sun4i-gpadc: use of_device_get_match_data 2017-10-21 18:48:00 +01:00
ti_am335x_adc.c Drivers:iio:adc:ti_am335x_adc remove comparison to bool 2018-01-08 16:03:43 +01:00
ti-adc081c.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ti-adc084s021.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ti-adc108s102.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ti-adc128s052.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ti-adc161s626.c iio: add SPDX identifier for various drivers 2018-02-18 11:55:19 +00:00
ti-adc0832.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
ti-adc12138.c iio: adc: adc12138: make array ch_to_mux static, makes object code smaller 2017-10-21 17:56:09 +01:00
ti-ads1015.c Merge 4.14-rc4 into staging-next 2017-10-09 09:02:35 +02:00
ti-ads7950.c iio: adc: ti-ads7950: use SPI_CS_WORD to reduce CPU usage 2018-09-22 10:09:47 +01:00
ti-ads8688.c iio: adc: ti-ads8688: add trigger and buffer support 2018-05-12 12:00:30 +01:00
ti-tlc4541.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
twl4030-madc.c Merge 4.14-rc4 into staging-next 2017-10-09 09:02:35 +02:00
twl6030-gpadc.c treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
vf610_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
viperboard_adc.c iio:adc: drop assign iio_info.driver_module and iio_trigger_ops.owner 2017-08-22 21:22:25 +01:00
xilinx-xadc-core.c iio: adc: xilinx: Move request_irq before enabling interrupts 2018-07-29 13:30:35 +01:00
xilinx-xadc-events.c iio: adc: xadc: Fix coding style violations 2017-08-12 13:10:30 +01:00
xilinx-xadc.h iio: adc: xilinx: Remove platform_get_irq from xadc_remove function 2018-07-29 12:52:21 +01:00