On 15.12.2017 00:41, Lucas Stach wrote: > Am Montag, den 11.12.2017, 18:26 +0300 schrieb Dmitry Osipenko: >> On 11.12.2017 17:27, Thierry Reding wrote: >>> On Mon, Dec 11, 2017 at 04:53:56PM +0300, Dmitry Osipenko wrote: >>>> On 11.12.2017 13:13, Thierry Reding wrote: >>>>> On Mon, Dec 11, 2017 at 02:19:44AM +0300, Dmitry Osipenko >>>>> wrote: >>>>>> Add manual HW power management to drivers probe/remove in >>>>>> order to >>>>>> not fail in a case of runtime power management being disabled >>>>>> in kernel >>>>>> config. >>>>>> >>>>>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx> >>>>>> --- >>>>>> drivers/gpu/drm/tegra/dc.c | 164 >>>>>> +++++++++++++++++++++++++++---------------- >>>>>> drivers/gpu/drm/tegra/dsi.c | 138 +++++++++++++++++++++-- >>>>>> ------------- >>>>>> drivers/gpu/drm/tegra/hdmi.c | 90 ++++++++++++++++-------- >>>>>> drivers/gpu/drm/tegra/sor.c | 103 +++++++++++++++++------ >>>>>> ---- >>>>>> 4 files changed, 310 insertions(+), 185 deletions(-) >>>>> >>>>> I think that's the wrong way around. We unconditionally select >>>>> PM on >>>>> 64-bit ARM already, and I think we should do the same on 32-bit >>>>> ARM. >>>>> There's really no excuse not to enable runtime PM these days. >>>> >>>> What is the rational behind enabling PM unconditionally? It is >>>> actually a very >>>> useful debug feature when there is something wrong with the PM. >>>> It looks like >>>> Tegra DRM driver is the only driver on Tegra that doesn't work >>>> properly with PM >>>> being disabled. Please, let's just fix it. >>> >>> What's useful about disabling PM? The problem with allowing !PM is >>> that >>> it adds one more combination that needs to be build- and runtime >>> tested. >> >> As I already stated, disabling PM is very useful for debugging when >> system hangs >> unexpectedly. I found it very helpful several times. > > This assumes that the bootloader/firmware left the power domains > powered up. Without PM_GENERIC_DOMAINS, which depends on CONFIG_PM the > kernel has no means to control the state of the power domains. Probe > deferral based on the power domain will also not work, so driver may > probe and try to access power-gated devices, leading to system hangs in > the common case. Pre-186 Tegra's do not use generic PM domains, but a custom API. Meanwhile T186 always has CONFIG_PM enabled. -- 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
