It appears bus errors and NACK counts are frequently found in many I2C controllers; a few I2C bus drivers now export those counters to debugfs. There is some effort in attempting to monitor a large number of BMCs (board management controllers) and we are wondering if it is possible to have a more stable and unified interface for those counters to be exported to compared to the debugfs, so that a single command can be used to obtain the counters from different types of I2C controllers. One possible prototype is included in the patchset where debug counters are populated in /sys/class/i2c-adapter/i2c-X/stats/. By default only an empty stats folder is created, and it is up to the platform drivers to instantiate the counters and link the counters to the data structures internal to the bus drivers. >From the kernel data structure point of view, the statistics are a property of an i2c_adapter (and not an i2c_dev). From the driver type point of view, the counters should only be instantiated by a platform driver (such as bus drivers) and not a device driver (such as mux drivers.) In this example, the npcm7xx driver instantiates the counters. The patchset is intended to request comments on whether the goal makes sense and what a good approach looks like. Patch 1: add i2c statistics to i2c_adapter Patch 2: instantiate i2c statistics from the npcm7xx i2c bus driver TODO: - Decide on which counters to be included (maybe start with BER and NACK?) - Use enums and not strings as counter names - Make binding more flexible so a counter can be backed by some function and not only pointer to a value The desired effect can be tested by building and running an OpenBMC distribution targeted at the npcm7xx SoC and running the image in QEMU. The testing steps are as follows: 1. Clone the OpenBMC repository 2. `devtool modify`and apply patch to the linux-nuvoton recipe 3. Build image for quanta-gsj 4. Build QEMU 5. Run the image-bmc image in QEMU Results: root@gsj:/sys/class/i2c-adapter/i2c-1/stats# ls ber_cnt i2c_speed nack_cnt rec_fail_cnt rec_succ_cnt timeout_cnt root@gsj:/sys/class/i2c-adapter/i2c-1/stats# cat * 0 100000 0 0 0 0 Patch list: Sui Chen (2): i2c debug counters as sysfs attributes add npcm7xx debug counters as sysfs attributes drivers/i2c/busses/i2c-npcm7xx.c | 8 ++++++++ drivers/i2c/i2c-core-base.c | 3 +++ drivers/i2c/i2c-dev.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 21 +++++++++++++++++++++ 4 files changed, 131 insertions(+)
