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f11a04464a
linux/drivers/i2c/busses
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Jan Kundrát f11a04464a i2c: gpio: Enable working over slow can_sleep GPIOs 
"Slow" GPIOs (usually those connected over an SPI or an I2C bus) are,
well, slow in their operation. It is generally a good idea to avoid
using them for time-critical operation, but sometimes the hardware just
sucks, and the software has to cope. In addition to that, the I2C bus
itself does not actually define any strict timing limits; the bus is
free to go all the way down to DC. The timeouts (and therefore the
slowest acceptable frequency) are present only in SMBus.

The `can_sleep` is IMHO a wrong concept to use here. My SPI-to-quad-UART
chip (MAX14830) is connected via a 26MHz SPI bus, and it happily drives
SCL at 200kHz (5µs pulses) during my benchmarks. That's faster than the
maximal allowed speed of the traditional I2C.

The previous version of this code did not really block operation over
slow GPIO pins, anyway. Instead, it just resorted to printing a warning
with a backtrace each time a GPIO pin was accessed, thereby slowing
things down even more.

Finally, it's not just me. A similar patch was originally submitted in
2015 [1].

[1] https://patchwork.ozlabs.org/patch/450956/

Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2018-01-04 01:02:55 +01:00
..
i2c-acorn.c
i2c-ali15x3.c Annotate hardware config module parameters in drivers/i2c/ 2017-04-20 12:02:32 +01:00
i2c-ali1535.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-ali1563.c i2c: ali1563: fix checkpatch.pl issues 2014-05-22 10:09:21 +02:00
i2c-altera.c i2c: altera: Add Altera I2C Controller driver 2017-09-13 23:37:16 +02:00
i2c-amd756-s4882.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-amd756.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-amd8111.c i2c: remove DEFINE_PCI_DEVICE_TABLE macro 2014-03-13 09:44:59 +01:00
i2c-aspeed.c i2c: aspeed: Deassert reset in probe 2017-11-06 19:15:31 +01:00
i2c-at91.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-au1550.c i2c: au1550: Convert to devm_kzalloc and devm_ioremap_resource 2015-10-23 23:31:11 +02:00
i2c-axxia.c i2c: constify i2c_adapter_quirks structures 2016-11-18 02:05:03 +01:00
i2c-bcm2835.c i2c: bcm2835: Avoid possible NULL ptr dereference 2017-02-20 19:19:54 +01:00
i2c-bcm-iproc.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-bcm-kona.c Merge branch 'i2c/for-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2016-10-07 14:12:21 -07:00
i2c-bfin-twi.c blackfin: merge the two TWI header files 2017-08-27 15:37:18 +02:00
i2c-brcmstb.c i2c: brcmstb: Fix START and STOP conditions 2017-03-08 18:00:49 +01:00
i2c-cadence.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-cbus-gpio.c i2c: busses: drop owner assignment from platform_drivers 2014-10-20 16:20:37 +02:00
i2c-cht-wc.c i2c-cht-wc: constify platform_device_id 2017-12-07 12:00:35 +01:00
i2c-cpm.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-cros-ec-tunnel.c i2c: i2c-cros-ec-tunnel: Reduce logging noise 2017-01-28 22:16:38 +01:00
i2c-davinci.c i2c/ARM: davinci: Deep refactoring of I2C recovery 2017-12-31 00:09:39 +01:00
i2c-designware-baytrail.c i2c: designware-baytrail: fix potential null pointer dereference on dev 2017-04-19 21:00:13 +02:00
i2c-designware-common.c i2c: designware: fix building driver as module 2017-11-28 10:44:19 +01:00
i2c-designware-core.h i2c: designware: add i2c gpio recovery option 2017-11-27 18:39:38 +01:00
i2c-designware-master.c i2c: designware: add i2c gpio recovery option 2017-11-27 18:39:38 +01:00
i2c-designware-pcidrv.c i2c: designware: MASTER mode as separated driver 2017-06-19 18:24:59 +02:00
i2c-designware-platdrv.c i2c: designware: rename i2c_dw_plat_prepare_clk to i2c_dw_prepare_clk 2017-11-27 18:39:30 +01:00
i2c-designware-slave.c i2c: designware: Don't set SCL timings and speed mode when in slave mode 2017-11-27 18:30:13 +01:00
i2c-digicolor.c i2c: digicolor: use clk_disable_unprepare instead of clk_unprepare 2016-11-18 01:48:01 +01:00
i2c-diolan-u2c.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-dln2.c i2c: constify i2c_adapter_quirks structures 2016-11-18 02:05:03 +01:00
i2c-efm32.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-eg20t.c i2c: busses: constify i2c_algorithm structures 2017-02-09 17:06:52 +01:00
i2c-elektor.c Annotate hardware config module parameters in drivers/i2c/ 2017-04-20 12:02:32 +01:00
i2c-emev2.c i2c: emev2: Handle return value of clk_prepare_enable 2017-06-19 22:18:55 +02:00
i2c-exynos5.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-gpio.c i2c: gpio: Enable working over slow can_sleep GPIOs 2018-01-04 01:02:55 +01:00
i2c-highlander.c i2c: busses: drop owner assignment from platform_drivers 2014-10-20 16:20:37 +02:00
i2c-hix5hd2.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-hydra.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-i801.c i2c: i801: Fix Failed to allocate irq -2147483648 error 2017-11-27 19:11:27 +01:00
i2c-ibm_iic.c sched/headers: Prepare to move signal wakeup & sigpending methods from <linux/sched.h> into <linux/sched/signal.h> 2017-03-02 08:42:32 +01:00
i2c-ibm_iic.h
i2c-img-scb.c i2c: img-scb: Add runtime PM 2017-10-28 14:03:45 +02:00
i2c-imx-lpi2c.c Merge branch 'i2c/for-4.11' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2017-02-25 14:21:18 -08:00
i2c-imx.c i2c: imx: Include the right GPIO header 2017-12-12 23:31:45 +01:00
i2c-iop3xx.c i2c: iop3xx: use new 8 bit address helper function 2016-04-11 18:54:59 +02:00
i2c-iop3xx.h i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-isch.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-ismt.c i2c: ismt: Use %pad specifier for dma_addr_t variables 2017-12-31 00:19:16 +01:00
i2c-jz4780.c i2c: jz4780: Fix module autoload 2016-10-25 11:48:58 +02:00
i2c-kempld.c i2c: busses: make i2c_adapter const 2017-08-29 22:26:08 +02:00
i2c-lpc2k.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-meson.c i2c: meson: improve and simplify interrupt handler 2017-03-30 17:31:29 +02:00
i2c-mlxcpld.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-mpc.c i2c: mpc: remove useless variable initialization 2017-11-01 23:51:49 +01:00
i2c-mt65xx.c i2c: mediatek: Enable i2c module clock before i2c registers access. 2018-01-04 00:54:02 +01:00
i2c-mv64xxx.c i2c: mv64xxx: explicitly request exclusive reset control 2017-08-14 21:40:07 +02:00
i2c-mxs.c i2c: mxs: change error printing to debug for mxs_i2c_pio_wait_xfer_end 2017-06-02 22:57:14 +02:00
i2c-nforce2-s4985.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-nforce2.c i2c: busses: constify i2c_algorithm structures 2017-02-09 17:06:52 +01:00
i2c-nomadik.c i2c: nomadik: constify amba_id 2017-08-29 22:35:14 +02:00
i2c-ocores.c i2c: busses: make i2c_adapter const 2017-08-29 22:26:08 +02:00
i2c-octeon-core.c i2c: octeon: thunderx: Limit register access retries 2016-12-17 19:27:44 +01:00
i2c-octeon-core.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
i2c-octeon-platdrv.c i2c: busses: make i2c_adapter const 2017-08-29 22:26:08 +02:00
i2c-omap.c i2c: omap: Trigger bus recovery in lockup case 2017-10-30 15:18:31 +01:00
i2c-opal.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-parport-light.c i2c: i2c-smbus: Use threaded irq for smbalert 2017-10-28 23:42:26 +02:00
i2c-parport.c i2c: i2c-smbus: Use threaded irq for smbalert 2017-10-28 23:42:26 +02:00
i2c-parport.h i2c: parport: Add VCT-jig adapter 2015-08-10 08:37:34 +02:00
i2c-pasemi.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-pca-isa.c Annotate hardware config module parameters in drivers/i2c/ 2017-04-20 12:02:32 +01:00
i2c-pca-platform.c i2c: pca-platform: propagate error from i2c_pca_add_numbered_bus 2017-07-04 16:03:42 +02:00
i2c-piix4.c i2c: piix4: Fix port number check on release 2017-12-12 23:27:04 +01:00
i2c-pmcmsp.c i2c: constify internal structures 2017-08-12 13:25:17 +02:00
i2c-pnx.c i2c/busses: Convert timers to use timer_setup() 2017-10-27 15:53:30 +02:00
i2c-powermac.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-puv3.c i2c: busses: make i2c_algorithm const 2017-08-29 22:20:20 +02:00
i2c-pxa-pci.c i2c: i2c-pxa-pci; make explicitly non-modular 2016-11-18 01:44:38 +01:00
i2c-pxa.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-qup.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-rcar.c i2c: rcar: skip DMA if buffer is not safe 2017-12-03 21:25:00 +01:00
i2c-riic.c i2c: riic: remove clock and frequency restrictions 2017-10-27 21:39:29 +02:00
i2c-rk3x.c i2c: rk3x: add support for rv1108 2017-08-12 16:39:47 +02:00
i2c-robotfuzz-osif.c i2c: busses: constify i2c_algorithm structures 2017-02-09 17:06:52 +01:00
i2c-s3c2410.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-scmi.c i2c: i2c-scmi: add a MS HID 2017-04-16 21:48:06 +02:00
i2c-sh7760.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-sh_mobile.c i2c: sh_mobile: use core helper to decide when to use DMA 2017-12-03 21:24:59 +01:00
i2c-sibyte.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-simtec.c i2c: simtec: use release_mem_region instead of release_resource 2017-08-14 21:39:21 +02:00
i2c-sirf.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-sis96x.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-sis630.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-sis5595.c Annotate hardware config module parameters in drivers/i2c/ 2017-04-20 12:02:32 +01:00
i2c-sprd.c i2c: ensure termination of *_device_id tables 2017-10-05 14:44:57 +02:00
i2c-st.c i2c: use dev_get_drvdata() to get private data in suspend/resume hooks 2017-07-31 17:03:32 +02:00
i2c-stm32.h i2c: stm32: Fix copyrights 2017-12-12 23:16:04 +01:00
i2c-stm32f4.c i2c: stm32: Fix copyrights 2017-12-12 23:16:04 +01:00
i2c-stm32f7.c i2c: stm32: Fix copyrights 2017-12-12 23:16:04 +01:00
i2c-stu300.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-sun6i-p2wi.c i2c: sun6i-pw2i: explicitly request exclusive reset control 2017-08-14 21:40:21 +02:00
i2c-taos-evm.c i2c: taos-evm: Remove duplicate NULL check 2017-11-02 00:01:21 +01:00
i2c-tegra-bpmp.c i2c: tegra: fix spelling mistake: "contoller" -> "controller" 2017-04-21 14:04:57 +02:00
i2c-tegra.c i2c: busses: make i2c_adapter_quirks const 2017-08-29 22:32:47 +02:00
i2c-thunderx-pcidrv.c i2c: thunderx: Remove duplicate NULL check 2017-11-02 00:01:31 +01:00
i2c-tiny-usb.c i2c: i2c-tiny-usb: fix buffer not being DMA capable 2017-05-22 10:33:42 +02:00
i2c-uniphier-f.c i2c: uniphier-f: add suspend / resume support 2017-08-12 15:38:23 +02:00
i2c-uniphier.c i2c: uniphier: add suspend / resume support 2017-08-12 15:38:13 +02:00
i2c-versatile.c i2c: versatile: Make i2c_algo_bit_data const 2017-08-29 22:34:12 +02:00
i2c-via.c i2c: remove FSF address 2014-11-07 18:35:33 +01:00
i2c-viapro.c Annotate hardware config module parameters in drivers/i2c/ 2017-04-20 12:02:32 +01:00
i2c-viperboard.c i2c: constify i2c_adapter_quirks structures 2016-11-18 02:05:03 +01:00
i2c-wmt.c i2c: don't print error when adding adapter fails 2016-08-22 08:19:55 +02:00
i2c-xgene-slimpro.c i2c: xgene-slimpro: Support v2 2017-11-01 23:54:53 +01:00
i2c-xiic.c i2c: busses: make i2c_adapter const 2017-08-29 22:26:08 +02:00
i2c-xlp9xx.c i2c: xlp9xx: Handle I2C_M_RECV_LEN in msg->flags 2017-10-17 23:53:28 +02:00
i2c-xlr.c i2c: busses: constify i2c_algorithm structures 2017-02-09 17:06:52 +01:00
i2c-zx2967.c i2c: zx2967: always use the same device when printing errors 2017-06-27 23:21:00 +02:00
Kconfig i2c: gpio: add fault injector 2017-12-03 20:33:29 +01:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
scx200_acb.c Annotate hardware config module parameters in drivers/i2c/ 2017-04-20 12:02:32 +01:00