Commit 4141cf67 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'i2c/for-4.16' of git://

Pull i2c updates from Wolfram Sang:
 "I2C has the following changes for you:

   - new flag to mark DMA safe buffers in i2c_msg. Also, some
     infrastructure around it. And docs.

   - huge refactoring of the at24 driver led by the new maintainer

   - update I2C bus recovery to send STOP after recovery

   - conversion from gpio to gpiod for I2C bus recovery

   - adding a fault-injector to the i2c-gpio driver

   - lots of small driver improvements, and bigger ones to

* 'i2c/for-4.16' of git:// (99 commits)
  i2c: mv64xxx: Add myself as maintainer for this driver
  i2c: mv64xxx: Fix clock resource by adding an optional bus clock
  i2c: mv64xxx: Remove useless test before clk_disable_unprepare
  i2c: mxs: use true and false for boolean values
  i2c: meson: update doc description to fix build warnings
  i2c: meson: add configurable divider factors
  dt-bindings: i2c: update documentation for the Meson-AXG
  i2c: imx-lpi2c: add runtime pm support
  i2c: rcar: fix some trivial typos in comments
  i2c: davinci: fix the cpufreq transition
  i2c: rk3x: add proper kerneldoc header
  i2c: rk3x: account for const type of
  i2c: acorn: remove outdated path from file header
  i2c: acorn: add MODULE_LICENSE tag
  i2c: rcar: implement bus recovery
  i2c: send STOP after successful bus recovery
  i2c: ensure SDA is released in recovery if SDA is controllable
  i2c: add 'set_sda' to bus_recovery_info
  i2c: add identifier in declarations for i2c_bus_recovery
  i2c: make kerneldoc about bus recovery more precise
parents 3462ac57 e38c8564
Required properties:
- compatible: Must be a "<manufacturer>,<model>" pair. The following <model>
values are supported (assuming "atmel" as manufacturer):
If <manufacturer> is not "atmel", then a fallback must be used
with the same <model> and "atmel" as manufacturer.
compatible = "microchip,24c128", "atmel,24c128";
Supported manufacturers are:
Some vendors use different model names for chips which are just
variants of the above. Known such exceptions are listed below:
"renesas,r1ex24002" - the fallback is "atmel,24c02"
- reg: The I2C address of the EEPROM.
Optional properties:
- pagesize: The length of the pagesize for writing. Please consult the
manual of your device, that value varies a lot. A wrong value
may result in data loss! If not specified, a safety value of
'1' is used which will be very slow.
- read-only: This parameterless property disables writes to the eeprom.
- size: Total eeprom size in bytes.
- no-read-rollover: This parameterless property indicates that the
multi-address eeprom does not automatically roll over
reads to the next slave address. Please consult the
manual of your device.
- wp-gpios: GPIO to which the write-protect pin of the chip is connected.
eeprom@52 {
compatible = "atmel,24c32";
reg = <0x52>;
pagesize = <32>;
wp-gpios = <&gpio1 3 0>;
Required properties:
- compatible : should be "<manufacturer>,<type>", like these:
"atmel,24c00", "atmel,24c01", "atmel,24c02", "atmel,24c04",
"atmel,24c08", "atmel,24c16", "atmel,24c32", "atmel,24c64",
"atmel,24c128", "atmel,24c256", "atmel,24c512", "atmel,24c1024"
The following manufacturers values have been deprecated:
"at", "at24"
If there is no specific driver for <manufacturer>, a generic
device with <type> and manufacturer "atmel" should be used.
Possible types are:
"24c00", "24c01", "24c02", "24c04", "24c08", "24c16", "24c32", "24c64",
"24c128", "24c256", "24c512", "24c1024", "spd"
- reg : the I2C address of the EEPROM
Optional properties:
- pagesize : the length of the pagesize for writing. Please consult the
manual of your device, that value varies a lot. A wrong value
may result in data loss! If not specified, a safety value of
'1' is used which will be very slow.
- read-only: this parameterless property disables writes to the eeprom
- size: total eeprom size in bytes
eeprom@52 {
compatible = "atmel,24c32";
reg = <0x52>;
pagesize = <32>;
Amlogic Meson I2C controller
Required properties:
- compatible: must be "amlogic,meson6-i2c" or "amlogic,meson-gxbb-i2c"
- compatible: must be:
"amlogic,meson6-i2c" for Meson8 and compatible SoCs
"amlogic,meson-gxbb-i2c" for GXBB and compatible SoCs
"amlogic,meson-axg-i2c"for AXG and compatible SoCs
- reg: physical address and length of the device registers
- interrupts: a single interrupt specifier
- clocks: clock for the device
......@@ -5,6 +5,7 @@ The MediaTek's I2C controller is used to interface with I2C devices.
Required properties:
- compatible: value should be either of the following.
"mediatek,mt2701-i2c", "mediatek,mt6577-i2c": for MediaTek MT2701
"mediatek,mt2712-i2c": for MediaTek MT2712
"mediatek,mt6577-i2c": for MediaTek MT6577
"mediatek,mt6589-i2c": for MediaTek MT6589
"mediatek,mt7622-i2c": for MediaTek MT7622
* NXP PCA954x I2C bus switch
The driver supports NXP PCA954x and PCA984x I2C mux/switch devices.
Required Properties:
- compatible: Must contain one of the following.
"nxp,pca9540", "nxp,pca9542", "nxp,pca9543", "nxp,pca9544",
"nxp,pca9545", "nxp,pca9546", "nxp,pca9547", "nxp,pca9548"
"nxp,pca9546", "nxp,pca9846",
"nxp,pca9547", "nxp,pca9847",
"nxp,pca9548", "nxp,pca9848",
- reg: The I2C address of the device.
......@@ -25,6 +25,15 @@ default frequency is 100kHz
whenever you're using the "allwinner,sun6i-a31-i2c"
- clocks: : pointers to the reference clocks for this device, the
first one is the one used for the clock on the i2c bus,
the second one is the clock used to acces the registers
of the controller
- clock-names : names of used clocks, mandatory if the second clock is
used, the name must be "core", and "reg" (the latter is
only for Armada 7K/8K).
i2c@11000 {
......@@ -42,3 +51,14 @@ For the Armada XP:
interrupts = <29>;
clock-frequency = <100000>;
For the Armada 7040:
i2c@701000 {
compatible = "marvell,mv78230-i2c";
reg = <0x701000 0x20>;
interrupts = <29>;
clock-frequency = <100000>;
clock-names = "core", "reg";
clocks = <&core_clock>, <&reg_clock>;
Linux I2C and DMA
Given that i2c is a low-speed bus, over which the majority of messages
transferred are small, it is not considered a prime user of DMA access. At this
time of writing, only 10% of I2C bus master drivers have DMA support
implemented. And the vast majority of transactions are so small that setting up
DMA for it will likely add more overhead than a plain PIO transfer.
Therefore, it is *not* mandatory that the buffer of an I2C message is DMA safe.
It does not seem reasonable to apply additional burdens when the feature is so
rarely used. However, it is recommended to use a DMA-safe buffer if your
message size is likely applicable for DMA. Most drivers have this threshold
around 8 bytes (as of today, this is mostly an educated guess, however). For
any message of 16 byte or larger, it is probably a really good idea. Please
note that other subsystems you use might add requirements. E.g., if your
I2C bus master driver is using USB as a bridge, then you need to have DMA
safe buffers always, because USB requires it.
For clients, if you use a DMA safe buffer in i2c_msg, set the I2C_M_DMA_SAFE
flag with it. Then, the I2C core and drivers know they can safely operate DMA
on it. Note that using this flag is optional. I2C host drivers which are not
updated to use this flag will work like before. And like before, they risk
using an unsafe DMA buffer. To improve this situation, using I2C_M_DMA_SAFE in
more and more clients and host drivers is the planned way forward. Note also
that setting this flag makes only sense in kernel space. User space data is
copied into kernel space anyhow. The I2C core makes sure the destination
buffers in kernel space are always DMA capable. Also, when the core emulates
SMBus transactions via I2C, the buffers for block transfers are DMA safe. Users
of i2c_master_send() and i2c_master_recv() functions can now use DMA safe
variants (i2c_master_send_dmasafe() and i2c_master_recv_dmasafe()) once they
know their buffers are DMA safe. Users of i2c_transfer() must set the
I2C_M_DMA_SAFE flag manually.
Bus master drivers wishing to implement safe DMA can use helper functions from
the I2C core. One gives you a DMA-safe buffer for a given i2c_msg as long as a
certain threshold is met::
dma_buf = i2c_get_dma_safe_msg_buf(msg, threshold_in_byte);
If a buffer is returned, it is either msg->buf for the I2C_M_DMA_SAFE case or a
bounce buffer. But you don't need to care about that detail, just use the
returned buffer. If NULL is returned, the threshold was not met or a bounce
buffer could not be allocated. Fall back to PIO in that case.
In any case, a buffer obtained from above needs to be released. It ensures data
is copied back to the message and a potentially used bounce buffer is freed::
i2c_release_dma_safe_msg_buf(msg, dma_buf);
The bounce buffer handling from the core is generic and simple. It will always
allocate a new bounce buffer. If you want a more sophisticated handling (e.g.
reusing pre-allocated buffers), you are free to implement your own.
Please also check the in-kernel documentation for details. The i2c-sh_mobile
driver can be used as a reference example how to use the above helpers.
Final note: If you plan to use DMA with I2C (or with anything else, actually)
make sure you have CONFIG_DMA_API_DEBUG enabled during development. It can help
you find various issues which can be complex to debug otherwise.
Linux I2C fault injection
The GPIO based I2C bus master driver can be configured to provide fault
injection capabilities. It is then meant to be connected to another I2C bus
which is driven by the I2C bus master driver under test. The GPIO fault
injection driver can create special states on the bus which the other I2C bus
master driver should handle gracefully.
Once the Kconfig option I2C_GPIO_FAULT_INJECTOR is enabled, there will be an
'i2c-fault-injector' subdirectory in the Kernel debugfs filesystem, usually
mounted at /sys/kernel/debug. There will be a separate subdirectory per GPIO
driven I2C bus. Each subdirectory will contain files to trigger the fault
injection. They will be described now along with their intended use-cases.
By reading this file, you get the current state of SCL. By writing, you can
change its state to either force it low or to release it again. So, by using
"echo 0 > scl" you force SCL low and thus, no communication will be possible
because the bus master under test will not be able to clock. It should detect
the condition of SCL being unresponsive and report an error to the upper
By reading this file, you get the current state of SDA. By writing, you can
change its state to either force it low or to release it again. So, by using
"echo 0 > sda" you force SDA low and thus, data cannot be transmitted. The bus
master under test should detect this condition and trigger a bus recovery (see
I2C specification version 4, section 3.1.16) using the helpers of the Linux I2C
core (see 'struct bus_recovery_info'). However, the bus recovery will not
succeed because SDA is still pinned low until you manually release it again
with "echo 1 > sda". A test with an automatic release can be done with the
'incomplete_transfer' file.
This file is write only and you need to write the address of an existing I2C
client device to it. Then, a transfer to this device will be started, but it
will stop at the ACK phase after the address of the client has been
transmitted. Because the device will ACK its presence, this results in SDA
being pulled low by the device while SCL is high. So, similar to the "sda" file
above, the bus master under test should detect this condition and try a bus
recovery. This time, however, it should succeed and the device should release
SDA after toggling SCL. Please note: there are I2C client devices which detect
a stuck SDA on their side and release it on their own after a few milliseconds.
Also, there are external devices deglitching and monitoring the I2C bus. They
can also detect a stuck SDA and will init a bus recovery on their own. If you
want to implement bus recovery in a bus master driver, make sure you checked
your hardware setup carefully before.
......@@ -2288,7 +2288,9 @@ F: include/linux/async_tx.h
M: Bartosz Golaszewski <>
T: git git://
S: Maintained
F: Documentation/devicetree/bindings/eeprom/at24.txt
F: drivers/misc/eeprom/at24.c
F: include/linux/platform_data/at24.h
......@@ -6580,6 +6582,12 @@ F: drivers/i2c/i2c-mux.c
F: drivers/i2c/muxes/
F: include/linux/i2c-mux.h
M: Gregory CLEMENT <>
S: Maintained
F: drivers/i2c/busses/i2c-mv64xxx.c
M: Jean Delvare <>
......@@ -17,6 +17,7 @@
#include <linux/mtd/rawnand.h>
#include <linux/i2c.h>
#include <linux/gpio.h>
#include <linux/gpio/machine.h>
#include <linux/clk.h>
#include <linux/videodev2.h>
#include <media/i2c/tvp514x.h>
......@@ -108,11 +109,20 @@ static struct platform_device davinci_nand_device = {
static struct gpiod_lookup_table i2c_recovery_gpiod_table = {
.dev_id = "i2c_davinci",
.table = {
GPIO_LOOKUP("davinci_gpio", 15, "sda",
GPIO_LOOKUP("davinci_gpio", 14, "scl",
static struct davinci_i2c_platform_data i2c_pdata = {
.bus_freq = 400 /* kHz */,
.bus_delay = 0 /* usec */,
.sda_pin = 15,
.scl_pin = 14,
.gpio_recovery = true,
static int dm355evm_mmc_gpios = -EINVAL;
......@@ -141,6 +151,7 @@ static struct i2c_board_info dm355evm_i2c_info[] = {
static void __init evm_init_i2c(void)
gpio_request(5, "dm355evm_msp");
......@@ -13,6 +13,7 @@
#include <linux/dma-mapping.h>
#include <linux/platform_device.h>
#include <linux/gpio.h>
#include <linux/gpio/machine.h>
#include <linux/i2c.h>
#include <linux/platform_data/pcf857x.h>
#include <linux/platform_data/at24.h>
......@@ -595,18 +596,28 @@ static struct i2c_board_info __initdata i2c_info[] = {
static struct gpiod_lookup_table i2c_recovery_gpiod_table = {
.dev_id = "i2c_davinci",
.table = {
GPIO_LOOKUP("davinci_gpio", 44, "sda",
GPIO_LOOKUP("davinci_gpio", 43, "scl",
/* The msp430 uses a slow bitbanged I2C implementation (ergo 20 KHz),
* which requires 100 usec of idle bus after i2c writes sent to it.
static struct davinci_i2c_platform_data i2c_pdata = {
.bus_freq = 20 /* kHz */,
.bus_delay = 100 /* usec */,
.sda_pin = 44,
.scl_pin = 43,
.gpio_recovery = true,
static void __init evm_init_i2c(void)
i2c_register_board_info(1, i2c_info, ARRAY_SIZE(i2c_info));
......@@ -649,6 +649,11 @@ static int __i2c_bit_add_bus(struct i2c_adapter *adap,
if (bit_adap->getscl == NULL)
adap->quirks = &i2c_bit_quirk_no_clk_stretch;
/* Bring bus to a known state. Looks like STOP if bus is not free yet */
setscl(bit_adap, 1);
setsda(bit_adap, 1);
ret = add_adapter(adap);
if (ret < 0)
return ret;
......@@ -603,6 +603,14 @@ config I2C_GPIO
This is a very simple bitbanging I2C driver utilizing the
arch-neutral GPIO API to control the SCL and SDA lines.
bool "GPIO-based fault injector"
depends on I2C_GPIO
This adds some functionality to the i2c-gpio driver which can inject
faults to an I2C bus, so another bus master can be stress-tested.
This is for debugging. If unsure, say 'no'.
tristate "Highlander FPGA SMBus interface"
depends on SH_HIGHLANDER
* linux/drivers/acorn/char/i2c.c
* ARM IOC/IOMD i2c driver.
* Copyright (C) 2000 Russell King
......@@ -7,8 +7,6 @@
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
* ARM IOC/IOMD i2c driver.
* On Acorn machines, the following i2c devices are on the bus:
* - PCF8583 real time clock & static RAM
......@@ -94,3 +92,7 @@ static int __init i2c_ioc_init(void)
MODULE_AUTHOR("Russell King <>");
......@@ -33,7 +33,7 @@
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/cpufreq.h>
#include <linux/gpio.h>
#include <linux/gpio/consumer.h>
#include <linux/of_device.h>
#include <linux/platform_data/i2c-davinci.h>
#include <linux/pm_runtime.h>
......@@ -139,7 +139,6 @@ struct davinci_i2c_dev {
u8 terminate;
struct i2c_adapter adapter;
struct completion xfr_complete;
struct notifier_block freq_transition;
struct davinci_i2c_platform_data *pdata;
......@@ -294,7 +293,7 @@ static int i2c_davinci_init(struct davinci_i2c_dev *dev)
* This routine does i2c bus recovery by using i2c_generic_gpio_recovery
* This routine does i2c bus recovery by using i2c_generic_scl_recovery
* which is provided by I2C Bus recovery infrastructure.
static void davinci_i2c_prepare_recovery(struct i2c_adapter *adap)
......@@ -316,7 +315,7 @@ static void davinci_i2c_unprepare_recovery(struct i2c_adapter *adap)
static struct i2c_bus_recovery_info davinci_i2c_gpio_recovery_info = {
.recover_bus = i2c_generic_gpio_recovery,
.recover_bus = i2c_generic_scl_recovery,
.prepare_recovery = davinci_i2c_prepare_recovery,
.unprepare_recovery = davinci_i2c_unprepare_recovery,
......@@ -567,9 +566,6 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
ret = num;
......@@ -717,13 +713,15 @@ static int i2c_davinci_cpufreq_transition(struct notifier_block *nb,
struct davinci_i2c_dev *dev;
dev = container_of(nb, struct davinci_i2c_dev, freq_transition);
davinci_i2c_reset_ctrl(dev, 0);
} else if (val == CPUFREQ_POSTCHANGE) {
davinci_i2c_reset_ctrl(dev, 1);
return 0;
......@@ -769,6 +767,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
struct davinci_i2c_dev *dev;
struct i2c_adapter *adap;
struct resource *mem;
struct i2c_bus_recovery_info *rinfo;
int r, irq;
irq = platform_get_irq(pdev, 0);
......@@ -789,9 +788,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
dev->dev = &pdev->dev;
dev->irq = irq;
dev->pdata = dev_get_platdata(&pdev->dev);
......@@ -868,10 +865,20 @@ static int davinci_i2c_probe(struct platform_device *pdev)
if (dev->pdata->has_pfunc)
adap->bus_recovery_info = &davinci_i2c_scl_recovery_info;
else if (dev->pdata->scl_pin) {
adap->bus_recovery_info = &davinci_i2c_gpio_recovery_info;
adap->bus_recovery_info->scl_gpio = dev->pdata->scl_pin;
adap->bus_recovery_info->sda_gpio = dev->pdata->sda_pin;
else if (dev->pdata->gpio_recovery) {
rinfo = &davinci_i2c_gpio_recovery_info;
adap->bus_recovery_info = rinfo;
rinfo->scl_gpiod = devm_gpiod_get(&pdev->dev, "scl",
if (IS_ERR(rinfo->scl_gpiod)) {
r = PTR_ERR(rinfo->scl_gpiod);
goto err_unuse_clocks;
rinfo->sda_gpiod = devm_gpiod_get(&pdev->dev, "sda", GPIOD_IN);
if (IS_ERR(rinfo->sda_gpiod)) {
r = PTR_ERR(rinfo->sda_gpiod);
goto err_unuse_clocks;
adap->nr = pdev->id;
......@@ -21,6 +21,7 @@
* ----------------------------------------------------------------------------
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <linux/errno.h>
......@@ -185,6 +186,19 @@ unsigned long i2c_dw_clk_rate(struct dw_i2c_dev *dev)
return dev->get_clk_rate_khz(dev);
int i2c_dw_prepare_clk(struct dw_i2c_dev *dev, bool prepare)
if (IS_ERR(dev->clk))
return PTR_ERR(dev->clk);
if (prepare)
return clk_prepare_enable(dev->clk);
return 0;
int i2c_dw_acquire_lock(struct dw_i2c_dev *dev)
int ret;
......@@ -217,7 +231,11 @@ int i2c_dw_wait_bus_not_busy(struct dw_i2c_dev *dev)
while (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY) {
if (timeout <= 0) {
dev_warn(dev->dev, "timeout waiting for bus ready\n");
return -ETIMEDOUT;
if (dw_readl(dev, DW_IC_STATUS) & DW_IC_STATUS_ACTIVITY)
return -ETIMEDOUT;
return 0;