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| author | Yijie Yang <yijie.yang@oss.qualcomm.com> | 2026-08-11 16:46:47 +0800 |
|---|---|---|
| committer | Rob Herring (Arm) <robh@kernel.org> | 2026-08-15 15:46:52 -0500 |
| commit | e1c13aed4a1641550e8c9518c96f016e1d52d09b (patch) | |
| tree | 61c2297688373db165cc857b7c7adcb147a5c419 /Documentation/i2c/i2c-protocol.rst | |
| download | linux-stable-e1c13aed4a1641550e8c9518c96f016e1d52d09b.tar.gz linux-stable-e1c13aed4a1641550e8c9518c96f016e1d52d09b.zip | |
dt-bindings: interconnect: qcom-bwmon: Add Maili cpu-bwmon compatiblegrafted
Add the Qualcomm Maili SoC compatible string for the CPU bandwidth
monitor (BWMONv4). This falls back to the sdm845-bwmon compatible,
consistent with the existing pattern used by other recent SoCs such as
sm8750 and kaanapali.
Signed-off-by: Yijie Yang <yijie.yang@oss.qualcomm.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Reviewed-by: Jingyi Wang <jingyi.wang@oss.qualcomm.com>
Link: https://patch.msgid.link/20260811-bwmon-v2-1-80f7f150ab9e@oss.qualcomm.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Diffstat (limited to 'Documentation/i2c/i2c-protocol.rst')
| -rw-r--r-- | Documentation/i2c/i2c-protocol.rst | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/Documentation/i2c/i2c-protocol.rst b/Documentation/i2c/i2c-protocol.rst new file mode 100644 index 000000000..df0febfe6 --- /dev/null +++ b/Documentation/i2c/i2c-protocol.rst @@ -0,0 +1,96 @@ +================ +The I2C Protocol +================ + +This document is an overview of the basic I2C transactions and the kernel +APIs to perform them. + +Key to symbols +============== + +=============== ============================================================= +S Start condition +P Stop condition +Rd/Wr (1 bit) Read/Write bit. Rd equals 1, Wr equals 0. +A, NA (1 bit) Acknowledge (ACK) and Not Acknowledge (NACK) bit +Addr (7 bits) I2C 7 bit address. Note that this can be expanded to + get a 10 bit I2C address. +Data (8 bits) A plain data byte. + +[..] Data sent by I2C device, as opposed to data sent by the + host adapter. +=============== ============================================================= + + +Simple send transaction +======================= + +Implemented by i2c_master_send():: + + S Addr Wr [A] Data [A] Data [A] ... [A] Data [A] P + + +Simple receive transaction +========================== + +Implemented by i2c_master_recv():: + + S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P + + +Combined transactions +===================== + +Implemented by i2c_transfer(). + +They are just like the above transactions, but instead of a stop +condition P a start condition S is sent and the transaction continues. +An example of a byte read, followed by a byte write:: + + S Addr Rd [A] [Data] NA S Addr Wr [A] Data [A] P + + +Modified transactions +===================== + +The following modifications to the I2C protocol can also be generated by +setting these flags for I2C messages. With the exception of I2C_M_NOSTART, they +are usually only needed to work around device issues: + +I2C_M_IGNORE_NAK: + Normally message is interrupted immediately if there is [NA] from the + client. Setting this flag treats any [NA] as [A], and all of + message is sent. + These messages may still fail to SCL lo->hi timeout. + +I2C_M_NO_RD_ACK: + In a read message, master A/NA bit is skipped. + +I2C_M_NOSTART: + In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some + point. For example, setting I2C_M_NOSTART on the second partial message + generates something like:: + + S Addr Rd [A] [Data] NA Data [A] P + + If you set the I2C_M_NOSTART variable for the first partial message, + we do not generate Addr, but we do generate the start condition S. + This will probably confuse all other clients on your bus, so don't + try this. + + This is often used to gather transmits from multiple data buffers in + system memory into something that appears as a single transfer to the + I2C device but may also be used between direction changes by some + rare devices. + +I2C_M_REV_DIR_ADDR: + This toggles the Rd/Wr flag. That is, if you want to do a write, but + need to emit an Rd instead of a Wr, or vice versa, you set this + flag. For example:: + + S Addr Rd [A] Data [A] Data [A] ... [A] Data [A] P + +I2C_M_STOP: + Force a stop condition (P) after the message. Some I2C related protocols + like SCCB require that. Normally, you really don't want to get interrupted + between the messages of one transfer. |
