On 29/01/16 16:58, Mathieu Poirier wrote: > On 28 January 2016 at 09:33, Jon Hunter <jonathanh@xxxxxxxxxx> wrote: >> Currently, the function tegra_powergate_set() simply sets the desired >> powergate state but does not wait for the state to change. In most cases >> we should wait for the state to change before proceeding. Currently, there >> is a case for tegra114 and tegra124 devices where we do not wait when >> starting the secondary CPU as this is not necessary. However, this is only >> done at boot time and so waiting here will only have a small impact on >> boot time. Therefore, update tegra_powergate_set() to wait when setting >> the powergate. >> >> By adding this feature, we can also eliminate the polling loop from >> tegra30_boot_secondary(). >> >> A function has been added for checking the status of the powergate and >> so update the tegra_powergate_is_powered() to use this macro as well. >> >> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> >> --- >> arch/arm/mach-tegra/platsmp.c | 16 +++------------- >> drivers/soc/tegra/pmc.c | 9 ++++++++- >> 2 files changed, 11 insertions(+), 14 deletions(-) >> >> diff --git a/arch/arm/mach-tegra/platsmp.c b/arch/arm/mach-tegra/platsmp.c >> index f3f61dbbda97..75620ae73913 100644 >> --- a/arch/arm/mach-tegra/platsmp.c >> +++ b/arch/arm/mach-tegra/platsmp.c >> @@ -108,19 +108,9 @@ static int tegra30_boot_secondary(unsigned int cpu, struct task_struct *idle) >> * be un-gated by un-toggling the power gate register >> * manually. >> */ >> - if (!tegra_pmc_cpu_is_powered(cpu)) { >> - ret = tegra_pmc_cpu_power_on(cpu); >> - if (ret) >> - return ret; >> - >> - /* Wait for the power to come up. */ >> - timeout = jiffies + msecs_to_jiffies(100); >> - while (!tegra_pmc_cpu_is_powered(cpu)) { >> - if (time_after(jiffies, timeout)) >> - return -ETIMEDOUT; >> - udelay(10); >> - } >> - } >> + ret = tegra_pmc_cpu_power_on(cpu); >> + if (ret) >> + return ret; >> >> remove_clamps: >> /* CPU partition is powered. Enable the CPU clock. */ >> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c >> index 99cb2fdd29e1..35ee60fd17be 100644 >> --- a/drivers/soc/tegra/pmc.c >> +++ b/drivers/soc/tegra/pmc.c >> @@ -28,6 +28,7 @@ >> #include <linux/export.h> >> #include <linux/init.h> >> #include <linux/io.h> >> +#include <linux/iopoll.h> >> #include <linux/of.h> >> #include <linux/of_address.h> >> #include <linux/platform_device.h> >> @@ -186,6 +187,9 @@ static inline bool tegra_powergate_state(int id) >> */ >> static int tegra_powergate_set(unsigned int id, bool new_state) >> { >> + bool status; >> + int err; >> + >> mutex_lock(&pmc->powergates_lock); >> >> if (tegra_powergate_state(id) == new_state) { >> @@ -195,9 +199,12 @@ static int tegra_powergate_set(unsigned int id, bool new_state) >> >> tegra_pmc_writel(PWRGATE_TOGGLE_START | id, PWRGATE_TOGGLE); >> >> + err = readx_poll_timeout(tegra_powergate_state, id, status, >> + status == new_state, 10, 100000); >> + > > I understand (and agree) with the goal of this patch but I wonder (and > I don't know much about the system/context) if holding a mutex while > sleeping won't incur adverse effect on other parts of the system that > weren't use to see this wait. One way to fix this might be to use > "mutex_trylock()" and let callers retry as they see fit if an > operation is already in progress. I could unlock the mutex after writing the TOGGLE_START register. I don't believe that we need to waiting for a powergate to change before writing again. Jon -- 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