On Tue, 2011-05-24 at 16:45 -0700, Kevin Hilman wrote: > Hi Tomi, > > Tomi Valkeinen <tomi.valkeinen@xxxxxx> writes: > > > On Wed, 2011-05-18 at 17:41 +0300, Tomi Valkeinen wrote: > >> On Wed, 2011-05-18 at 16:24 +0200, Kevin Hilman wrote: > >> > >> > Looking closer at the code, a zero return happens only when > >> > > >> > 1) no hwmod associated to omap_device > >> > 2) no power domain associated to hwmod > >> > 3) power domain has not (yet) lost context > >> > > >> > None of these are actually error conditions per-se, and in all cases, it > >> > indidates that context has not been lost (or we can't tell if context > >> > has been lost.) > >> > >> If the pm code cannot tell whether the context has been lost or not, the > >> driver must assume it has been lost, do you agree? If so, the driver > >> must handle zero return value differently, and always restore context. > >> > >> > So I think the current code is correct. > >> > >> How is it correct if it returns an error even if no error has happened > >> =)? Either the code or the documentation is wrong. > >> > >> How about the wrap-around case? Does the loss count go back to zero? > > > > Any conclusion on this? > > Sorry for the lag... been travelling, and finally back home... > > You're right, the code is just wrong here and would lead to strange > return value checking in the callers to be correct. > > I think the best fix for this problem is to use a signed return value > which can wrap as expected, and then use return negative error codes > (e.g. -ENODEV). When I first saw this context_loss_count in Nokia's kernel tree, it was returning int and was called get_last_off_on_transaction_id. I wonder why it ended up returning u32 in mainline... > Care to send a patch? or do you have any other suggestions for a fix? Sure, I'll cook up a patch. Looking at other users of get_context_loss_count, I see that omap hsmmc is also using it. Interestingly hsmmc code uses the value returned from omap_pm_get_dev_context_loss_count() as int, and checks if the returned value is < 0. So changing omap_pm_get_dev_context_loss_count() to return an int would also "fix" hsmmc code =). Tomi -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
