On 7/22/2020 3:41 AM, Wolfram Sang wrote: > >>> + synchronize_irq(iproc_i2c->irq); >> >> If one takes a look at the I2C slave ISR routine, there are places where >> IRQ can be re-enabled in the ISR itself. What happens after we mask all >> slave interrupt and when 'synchronize_irq' is called, which I suppose is >> meant to wait for inflight interrupt to finish where there's a chance >> the interrupt can be re-enable again? How is one supposed to deal with that? > > I encountered the same problem with the i2c-rcar driver before I left > for my holidays. > I think the following sequence needs to be implemented to make this safe, i.e., after 'synchronize_irq', no further slave interrupt will be fired. In 'bcm_iproc_i2c_unreg_slave': 1. Set an atomic variable 'unreg_slave' (I'm bad in names so please come up with a better name than this) 2. Disable all slave interrupts 3. synchronize_irq 4. Set slave to NULL 5. Erase slave addresses In the ISR routine, it should always check against 'unreg_slave' before enabling any slave interrupt. If 'unreg_slave' is set, no slave interrupt should be re-enabled from within the ISR. I think the above sequence can ensure no further slave interrupt after 'synchronize_irq'. I suggested using an atomic variable instead of variable + spinlock due to the way how sync irq works, i.e., "If you use this function while holding a resource the IRQ handler may need you will deadlock.". Thanks, Ray >>> + iproc_i2c->slave = NULL; >>> + >>> /* Erase the slave address programmed */ >>> tmp = iproc_i2c_rd_reg(iproc_i2c, S_CFG_SMBUS_ADDR_OFFSET); >>> tmp &= ~BIT(S_CFG_EN_NIC_SMB_ADDR3_SHIFT); >>>
