On Thu, 31 Mar 2022 18:57:33 +0200 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. > > 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. Hi Klaus, Just thought I'd mention I'm also interested in MCTP over I2C emulation for a couple of projects: 1) DMTF SPDM - mostly as a second transport for the kernel stack alongside PCI DOE. 2) CXL FM-API - adding support for the Fabric Manager interfaces on emulated CXL switches which is also typically carried over MCTP. I was thinking of emulating a MCTP over PCI VDM but this has saved me going to the effort of doing that for now at least :) I have hacked a really really basic MCTP device together using this series and it all seems to be working with the kernel stack (subject to a few kernel driver bugs that I'll report / send fixes for next week). I'm cheating all over the place so far, (lots of hard coded values) but would be interested in a more flexible solution that might perhaps share infrastructure with your NVMe-MI work. Thanks, Jonathan > > 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 >
