Dear Mika, On Mon, 18 May 2015 11:28:23 +0300 Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> wrote: > On Fri, May 15, 2015 at 08:31:39PM +0800, Jisheng Zhang wrote: > > Commit 1fc2fe204cb9 ("i2c: designware: Add runtime PM hooks") adds > > runtime pm support using the same ops for system sleep and runtime pm. > > When suspend to ram, the i2c host may have been runtime suspended, thus > > i2c_dw_disable() hangs. > > It hangs because it has already been powered off, right? Either be powered off or clock gated or even both. > > > This patch fixes this issue by separating ops for system sleep pm and > > runtime pm, and in the system suspend/resume path, runtime pm apis are > > used to ensure the device is at correct state. > > I can see that this fixes the issue with the platform driver (as the > platform bus core doesn't power on the device automatically as opposed > to other buses, like PCI). However, I'm thinking that can we do better > here. > > Instead of powering the device on again, can't we leave it in low power > state? Recently added 'dev->power.direct_complete' may be used to > achieve that, I think. how to handle runtime suspended via just being clock gated? Currently the only solution is using the runtime pm apis to ensure the device is in a working state during s2ram. What's your opinion? Thanks, Jisheng -- 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