On 08/02/2013 02:09 AM, Joseph Lo wrote: > On Tue, 2013-07-30 at 06:51 +0800, Stephen Warren wrote: >> On 07/26/2013 03:15 AM, Joseph Lo wrote: >>> When the system suspends to LP1, the clock of the CPU would be switched to >>> CLK_M (12MHz Oscillator) during suspend/resume flow. The clock driver >>> needs to restore the clock of CPU after LP1 resume. >> >> It's unclear to me how the code change implements "restore the clock of >> the CPU". A register name of CCLKG_BURST_POLICY doesn't sound like it's >> anything to do with enabled/disabling the CPU clock, nor configuring its >> rate. What exactly does this register do, and hence what does this new >> code actually restore? >> > When system suspend to LP1, most of the PLLs was clock gated. Because we > didn't cut off the core power, the settings of PLL still keep there. But > we switch the clock source of CPU to CLK_M before shut off PLLs by > CCLKG_BURSY_POLICY register. So we need to resume it back to original > clock source by CCLKG_BURST_POLICY register. Or it would be keep in low > rate (CLK_M) after resume. OK, I guess the register name was badly chosen by HW. I'd like to see part of your description above in the patch description. How about replacing the patch description with: ---------- When the system suspends to LP1, the CPU clock source is switched to CLK_M (12MHz Oscillator) during suspend/resume flow[1]. The CPU clock source is controlled by the CCLKG_BURST_POLICY register, and hence this register must be restored during LP1 resume. ---------- [1] Question: where does this happen? This patch doesn't make that change. I wonder why the suspend path can't save this register, rather than implementing a separate suspend syscore op in the clock driver. Does the HW auto-switch the value in the register itself? >> Why don't Tegra20/30 need a similar change? > > For Tegra20/30, the same code had been implemented in the suspend/resume > function of tegra_cpu_car_ops. It restores the CPU clock ASAP when CPU > resume from a suspend state to get quick performance I believe. > > For Tegra114, the resume performance is cool (although we can't see it > in upstream kernel now, it still need some other functions.). We can > implement all the clock related suspend/resume function in the clock > driver. OK, I do see something similar in tegra20/30_cpu_clock_suspend/resume. Why can't this new code be part of the equivalent functions; does the Tegra114 suspend/resume code in mach-tegra/ not call tegra_cpu_car_ops.suspend/resume() in the same way it does on Tegra20/30? -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
