Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxx> writes: > On 05/29/2013 08:22 PM, Kevin Hilman wrote: >> Oleksandr Dmytryshyn <oleksandr.dmytryshyn@xxxxxx> writes: >> >>> Starting from the OMAP chips with version2 registers scheme there are >>> 2 registers (I2C_IRQENABLE_SET and I2C_IRQENABLE_CLR) to manage >>> interrupts instead of the older OMAP chips with old scheme which have >>> only one register (I2C_IE). Now we should use I2C_IRQENABLE_SET >>> register for enabling interrupts and I2C_IRQENABLE_CLR register for >>> disabling interrupts. >> Why? (changelogs should always answer the "why" question) >> >> IOW, what is broken without this change, how does it fail? And equally >> important, how is it currently working? >> >> Kevin >> >> > Hi, Kevin. > > If the i2c controller during suspend will generate an interrupt, it > can lead to unpredictable behaviour in the kernel. > > Based on the logic of the kernel code interrupts from i2c should be > prohibited during suspend. Kernel writes 0 to the I2C_IE register in > the omap_i2c_runtime_suspend() function. In the other side kernel > writes saved interrupt flags to the I2C_IE register in > omap_i2c_runtime_resume() function. I.e. interrupts should be disabled > during suspend. > > This works for chips with version1 registers scheme. Interrupts are > disabled during suspend. For chips with version2 scheme registers > writting 0 to the I2C_IE register does nothing (because now the > I2C_IRQENABLE_SET register is located at this address ). This register > is used to enable interrupts. For disabling interrupts > I2C_IRQENABLE_CLR register should be used. > > I've checked that interrupts in the i2c controller are still enabled > after writting 0 to the I2C_IE register. But with my patch interrupts > are disabled in the omap_i2c_runtime_suspend() function. Yes, I understand why your patch works, and it looks correct to me. My main concern is that the changelog is missing a detailed description of the problem that is being solved, as well as a summary of why this has ever worked. I guess we've just been lucky and not seen interrupts during suspend? Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
