diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/devicetree/bindings/eeprom/at24.txt | 78 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/eeprom/eeprom.txt | 47 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-meson.txt | 6 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-mtk.txt | 1 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt | 13 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt | 20 | ||||
| -rw-r--r-- | Documentation/i2c/DMA-considerations | 67 | ||||
| -rw-r--r-- | Documentation/i2c/gpio-fault-injection | 54 |
8 files changed, 236 insertions, 50 deletions
diff --git a/Documentation/devicetree/bindings/eeprom/at24.txt b/Documentation/devicetree/bindings/eeprom/at24.txt new file mode 100644 index 0000000..1812c84 --- /dev/null +++ b/Documentation/devicetree/bindings/eeprom/at24.txt @@ -0,0 +1,78 @@ +EEPROMs (I2C) + +Required properties: + + - compatible: Must be a "<manufacturer>,<model>" pair. The following <model> + values are supported (assuming "atmel" as manufacturer): + + "atmel,24c00", + "atmel,24c01", + "atmel,24cs01", + "atmel,24c02", + "atmel,24cs02", + "atmel,24mac402", + "atmel,24mac602", + "atmel,spd", + "atmel,24c04", + "atmel,24cs04", + "atmel,24c08", + "atmel,24cs08", + "atmel,24c16", + "atmel,24cs16", + "atmel,24c32", + "atmel,24cs32", + "atmel,24c64", + "atmel,24cs64", + "atmel,24c128", + "atmel,24c256", + "atmel,24c512", + "atmel,24c1024", + + If <manufacturer> is not "atmel", then a fallback must be used + with the same <model> and "atmel" as manufacturer. + + Example: + compatible = "microchip,24c128", "atmel,24c128"; + + Supported manufacturers are: + + "catalyst", + "microchip", + "ramtron", + "renesas", + "nxp", + "st", + + 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. + +Example: + +eeprom@52 { + compatible = "atmel,24c32"; + reg = <0x52>; + pagesize = <32>; + wp-gpios = <&gpio1 3 0>; +}; diff --git a/Documentation/devicetree/bindings/eeprom/eeprom.txt b/Documentation/devicetree/bindings/eeprom/eeprom.txt deleted file mode 100644 index 27f2bc1..0000000 --- a/Documentation/devicetree/bindings/eeprom/eeprom.txt +++ /dev/null @@ -1,47 +0,0 @@ -EEPROMs (I2C) - -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" - - "catalyst,24c32" - - "microchip,24c128" - - "ramtron,24c64" - - "renesas,r1ex24002" - - 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 - -Example: - -eeprom@52 { - compatible = "atmel,24c32"; - reg = <0x52>; - pagesize = <32>; -}; diff --git a/Documentation/devicetree/bindings/i2c/i2c-meson.txt b/Documentation/devicetree/bindings/i2c/i2c-meson.txt index 611b934..13d410d 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-meson.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-meson.txt @@ -1,7 +1,11 @@ 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 diff --git a/Documentation/devicetree/bindings/i2c/i2c-mtk.txt b/Documentation/devicetree/bindings/i2c/i2c-mtk.txt index ff7bf37..e199695 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-mtk.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-mtk.txt @@ -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 diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt index aa09704..34d9150 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-mux-pca954x.txt @@ -1,10 +1,19 @@ * 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,pca9540", + "nxp,pca9542", + "nxp,pca9543", + "nxp,pca9544", + "nxp,pca9545", + "nxp,pca9546", "nxp,pca9846", + "nxp,pca9547", "nxp,pca9847", + "nxp,pca9548", "nxp,pca9848", + "nxp,pca9849" - reg: The I2C address of the device. diff --git a/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt b/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt index 5c30026..0ffe65a 100644 --- a/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt +++ b/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt @@ -25,6 +25,15 @@ default frequency is 100kHz whenever you're using the "allwinner,sun6i-a31-i2c" compatible. + - 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). + Examples: 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>, <®_clock>; + }; diff --git a/Documentation/i2c/DMA-considerations b/Documentation/i2c/DMA-considerations new file mode 100644 index 0000000..966610a --- /dev/null +++ b/Documentation/i2c/DMA-considerations @@ -0,0 +1,67 @@ +================= +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. + +Clients +------- + +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. + +Masters +------- + +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. diff --git a/Documentation/i2c/gpio-fault-injection b/Documentation/i2c/gpio-fault-injection new file mode 100644 index 0000000..e0c4f77 --- /dev/null +++ b/Documentation/i2c/gpio-fault-injection @@ -0,0 +1,54 @@ +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. + +"scl" +----- + +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 +layers. + +"sda" +----- + +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. + +"incomplete_transfer" +--------------------- + +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. |
