Hi
On 06/26/2018 07:58 PM, Jae Hyun Yoo wrote:
BMC firmware should support some multi-master use cases such as multi-node,
IPMB, BMC-ME link and so on but the current ASPEED I2C driver is a bit
unstable for the multi-master use case. So this patch improves ASPEED I2C
driver to support the multi-master use case stably.
Changes:
* Added XFER_MODE status register checking logic into
aspeed_i2c_master_xfer to improve the current bus busy checking logic.
* Changed the order of enum aspeed_i2c_master_state and
enum aspeed_i2c_slave_state defines to make their initial values set to
ASPEED_I2C_MASTER_INACTIVE and ASPEED_I2C_SLAVE_STOP respectively.
In case of multi-master use with previous code, if a slave data comes
ahead of the first master xfer, master_state starts from an invalid
state. This change fixed the issue.
* Adjusted spin_lock scope to make it wrap the whole irq handler using
a single lock and unlock pair covers both master and slave handlers.
* Added irq_status variable as a member of the struct aspeed_i2c_bus to
collect handled interrupt bits throughout the master and the slave irq
handlers.
* Added control logic to put an order on calling the master and the slave
irq handlers based on their current states.
This does many unrelated looking changes in one patch making it more
vulnerable for potential multiple regressions. For instance busy
checking goes from single read to loop with 250 ms timeout in this patch
while changing also spin lock logic and interrupt handling.
Now if there is some regression it might be difficult to find what
change in this patch is causing it and more over things goes more
complicated if some other kind of regressions are found pointing into
the same commit.
I suggest splitting this into multiple smaller patches. For instance
having first simple conversions patches that are unlikely to cause a
regression like one patch adding '\n' to error print, another moving
irq_status variable into struct aspeed_i2c_bus and so on followed by
patches that change logic like busy checking, spin lock change and then
patch or more for multi-master support.
--
Jarkko
