Kalle Jokiniemi <kalle.jokiniemi@xxxxxxxxx> writes: > On Wed, 2009-09-30 at 19:36 +0300, Kevin Hilman wrote: >> Kalle Jokiniemi <kalle.jokiniemi@xxxxxxxxx> writes: >> >> > While waiting for completion of the i2c transfer, the >> > MPU could hit OFF mode and cause several msecs of >> > delay that made i2c transfers fail more often. The >> > extra delays and subsequent re-trys cause i2c clocks >> > to be active more often. This has also an negative >> > effect on power consumption. >> > >> > Added a constraint that allows MPU to wake up in few >> > hundred usecs, which is roughly the average i2c wait >> > period. >> > >> > The constraint function is passed as platform data from >> > plat-omap/i2c.c and applied only on OMAP34XX devices. >> >> Seems like the latency value should also be (optionally) passed in >> pdata so this can be experimented with per-platform. > > Well, it kind of is already, since we pass the function that sets the > latency from platform code. And that function has the latency > hard-coded. I see it now, I initially thought that hard-coded value was in the driver, not in plat-omap/i2c.c. > My though was to use little #ifdeffery in defining the > function (and latency) for say omap3, and omap4 platforms. > > If #ifdeffery is out of the question, we could define > omap3_i2c_set_mpu.. and omap4_i2c_set_mpu.. functions and pass one in > init according to some "if (cpu_is_omapxyz)" statement. I think omap1&2 > don't need any latency constraints (and cannot use them as there is no > pm-layer implementation for those). > > What do you think? I recommend setting the functions at runtime using cpu_is* and allowing the functino to be NULL on platforms that don't need it. Combined with the NULL check proposed by Jarkko that should work well. Kevin -- 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
