On nie, 2014-11-30 at 21:19 +0900, Tomasz Figa wrote: > Hi Krzysztof, > > 2014-11-28 23:08 GMT+09:00 Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>: > > On pią, 2014-11-28 at 15:04 +0100, Linus Walleij wrote: > >> On Wed, Nov 26, 2014 at 3:24 PM, Krzysztof Kozlowski > >> <k.kozlowski@xxxxxxxxxxx> wrote: > >> > >> > The audio subsystem on Exynos 5420 has separate clocks and GPIO. To > >> > operate properly on GPIOs the main block clock 'mau_epll' must be > >> > enabled. > >> > > >> > This was observed on Peach Pi/Pit and Arndale Octa (after enabling i2s0) > >> > after introducing runtime PM to pl330 DMA driver. After that commit the > >> > 'mau_epll' was gated, because the "amba" clock was disabled and there > >> > were no more users of mau_epll. > >> > > >> > The system hang just before probing i2s0 because > >> > samsung_pinmux_setup() tried to access memory from audss block which was > >> > gated. > >> > > >> > Add a clock property to the pinctrl driver and enable the clock during > >> > GPIO setup. During normal GPIO operations (set, get, set_direction) the > >> > clock is not enabled. > > Could you make sure that possibility of gating this clock is worth the > effort of adding gating code to all affected drivers? If there is no > significant change in power consumption maybe it could be simply keep > running all the time? I had an impression that last time you disliked such idea: http://www.spinics.net/lists/arm-kernel/msg338127.html That's why I developed these patches. Because keeping a clock always on, even when it is unused, is undesirable. Anyway, I did some simple measurements (after booting Arndale Octa to /bin/sh, idle): - with mau_epll gated: ~523 mA - with mau_epll always on: ~531 mA Keeping it on increases energy usage by 1.5% in idle (with measurement uncertainty ~0.4%). > Also isn't a similar problem happening due to power domains? I believe > the whole maudio block is located in a separate power domain but > somehow it doesn't get turned off? There is Maudio power domain... but I think it is not related here. Pinctrl driver does not have runtime PM and is not attached to a domain. I thought about other solution to this problem (with utilization of power domains): - add runtime PM to pinctrl and audss clocks, - attach pinctrl and audss clocks to maudio power domain, - enable the clock when power domain is turned on. However almost the same changes had to be added to pinctrl and audss clocks drivers (replace clock_enable() with pm_runtime_get_sync()). Best regards, Krzysztof -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
