On Mon, 17 Jan 2011, Russell King wrote: > On Mon, Jan 17, 2011 at 02:00:17PM -0700, Paul Walmsley wrote: > > On Mon, 17 Jan 2011, Russell King wrote: > > > On Mon, Jan 17, 2011 at 01:31:47PM -0700, Paul Walmsley wrote: > > > > > > > > OMAP15xx uses the MPU timer for its clocksource, since OMAP15xx doesn't > > > > have GPTIMERs or the 32k sync timer, and the MPU timer code in > > > > mach-omap1/time.c wasn't updated for sched_clock() support. > > > > > > > > Adding an init_fixed_sched_clock() into omap_init_clocksource() should > > > > fix the boot on OMAP15xx/7xx. > > > > > > No, it needs fixing properly. There's no reason the gpt clocksource > > > can't be used for sched_clock. > > > > There's a very good reason why it can't on OMAP15xx/7xx. GPTIMER/DMTIMER > > IP blocks are only present on OMAP1610 and later[1]. Nor is a > > SYNCTIMER_32K IP block present on OMAP15xx/7xx[2]. > > Yes I realise that. That doesn't negate what I said though. Let me > show you how to do it: ... > Both a GPT _and_ 32K sched_clock implementation together, selectable > at runtime or build time depending on what is selected. I'll give you > that it isn't nice code, but it does what's required. Right. I agree that it is possible to support both GPTIMER and 32KiHz clocksources at runtime. But there should be a third case in that code also, a case for the OMAP1 MPU Timer IP blocks. Of course, it would be technically possible to define "GPT"/"GPTIMER" to mean "MPU Timer" on OMAP15xx/OMAP7xx. However, later OMAP1 chips contain all three of the above-mentioned timer IP blocks: GPTIMERs[1], a SYNCTIMER_32K[2], and the MPU Timers[3]. Each of these timers also has distinct power, interconnect, and register access properties. So it seems less confusing to keep the MPU Timer case distinct from the GPTIMER/GPT case. - Paul 1. OMAP1611/12 Multimedia Processor Technical Reference Manual [SWPU066B], section 13.5, "Dual-Mode Timer" 2. OMAP1611/12 Multimedia Processor Technical Reference Manual [SWPU066B], section 13.6, "32-kHz Synchronized Timer" 3. OMAP1611/12 Multimedia Processor Technical Reference Manual [SWPU066B], section 13.4, "OMAP3.2 Operating System Timer" -- 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
