> On Mar 31, 2022, at 9:57 AM, Klaus Jensen <i...@irrelevant.dk> wrote: > > 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.
This is great, I’m attempting to use your changes right now for the same thing (MCTP). > > 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 When I try this with my system, it seems like the i2c-echo device takes over the bus but never echoes the data to the EEPROM. Am I missing something to make this work? It seems like the “i2c_send_async” calls aren’t happening, which must be because the bottom half isn’t being scheduled, right? After the i2c_do_start_transfer, how is the bottom half supposed to be scheduled again? Is the slave receiving (the EEPROM) supposed to call i2c_ack or something? root@bmc-oob:~# echo 24c02 0x1064 > /sys/bus/i2c/devices/i2c-8/new_device [ 135.559719] at24 8-1064: 256 byte 24c02 EEPROM, writable, 1 bytes/write [ 135.562661] i2c i2c-8: new_device: Instantiated device 24c02 at 0x64 root@bmc-oob:~# i2cset -y 8 0x42 0x64 0x00 0xaa i i2c_echo_event: start send i2c_echo_send: data[0] = 0x64 i2c_echo_send: data[1] = 0x00 i2c_echo_send: data[2] = 0xaa i2c_echo_event: scheduling bottom-half i2c_echo_bh: attempting to gain mastery of bus i2c_echo_bh: starting a send to address 0x64 root@bmc-oob:~# hexdump -C /sys/bus/i2c/devices/8-1064/eeprom 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000100 Thanks again for this, it’s exactly what I needed. > > [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 > >
