From: Klaus Jensen <k.jen...@samsung.com> Hi all,
This RFC series adds I2C "slave mode" support for the Aspeed I2C controller as well as the necessary infrastructure in the i2c core to support this. Background ~~~~~~~~~~ We are working on an emulated NVM Express Management Interface[1] for testing and validation purposes. NVMe-MI is based on the MCTP protocol[2] which may use a variety of underlying transports. The one we are interested in is I2C[3]. The first general trickery here is that all MCTP transactions are based on the SMBus Block Write bus protocol[4]. This means that the slave must be able to master the bus to communicate. As you know, hw/i2c/core.c currently does not support this use case. The second issue is how to interact with these mastering devices. Jeremy and Matt (CC'ed) have been working on an MCTP stack for the Linux Kernel (already upstream) and an I2C binding driver[5] is currently under review. This binding driver relies on I2C slave mode support in the I2C controller. This series ~~~~~~~~~~~ Patch 1 adds support for multiple masters in the i2c core, allowing slaves to master the bus and safely issue i2c_send/recv(). Patch 2 adds an asynchronous send i2c_send_async(I2CBus *, uint8) on the bus that must be paired with an explicit ack using i2c_ack(I2CBus *). Patch 3 adds the slave mode functionality to the emulated Aspeed I2C controller. The implementation is probably buggy since I had to rely on the implementation of the kernel driver to reverse engineer the behavior of the controller slave mode (I do not have access to a spec sheet for the Aspeed, but maybe someone can help me out with that?). Finally, patch 4 adds an example device using this new API. The device is a simple "echo" device that upon being sent a set of bytes uses the first byte as the address of the slave to echo to. With this combined I am able to boot up Linux on an emulated Aspeed 2600 evaluation board and have the i2c echo device write into a Linux slave EEPROM. Assuming the echo device is on address 0x42: # echo slave-24c02 0x1064 > /sys/bus/i2c/devices/i2c-15/new_device i2c i2c-15: new_device: Instantiated device slave-24c02 at 0x64 # i2cset -y 15 0x42 0x64 0x00 0xaa i # hexdump /sys/bus/i2c/devices/15-1064/slave-eeprom 0000000 ffaa ffff ffff ffff ffff ffff ffff ffff 0000010 ffff ffff ffff ffff ffff ffff ffff ffff * 0000100 [1]: https://nvmexpress.org/developers/nvme-mi-specification/ [2]: https://www.dmtf.org/sites/default/files/standards/documents/DSP0236_1.3.1.pdf [3]: https://www.dmtf.org/sites/default/files/standards/documents/DSP0237_1.2.0.pdf [4]: http://www.smbus.org/specs/SMBus_3_1_20180319.pdf [5]: https://lore.kernel.org/linux-i2c/20220218055106.1944485-1-m...@codeconstruct.com.au/ Klaus Jensen (4): hw/i2c: support multiple masters hw/i2c: add async send hw/i2c: add slave mode for aspeed_i2c hw/misc: add a toy i2c echo device hw/i2c/aspeed_i2c.c | 95 +++++++++++++++++++++--- hw/i2c/core.c | 57 +++++++++++++- hw/i2c/trace-events | 2 +- hw/misc/i2c-echo.c | 144 ++++++++++++++++++++++++++++++++++++ hw/misc/meson.build | 2 + include/hw/i2c/aspeed_i2c.h | 8 ++ include/hw/i2c/i2c.h | 19 +++++ 7 files changed, 316 insertions(+), 11 deletions(-) create mode 100644 hw/misc/i2c-echo.c -- 2.35.1