On 7/22/2020 8:51 AM, Ray Jui wrote: > > 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 Actually, thinking about it more, 1. and 2. here need to be an atomic operation so it needs to be wrapped by a spin lock/unlock (and it is safe to do so here before calling synchronize_irq below). Same applies to the two read-modify-write sequneces to enable some of the slave interrupts in the 'bcm_iproc_i2c_slave_isr' routine. > > 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); >>>>
