Re: [PATCH V4 06/16] soc: tegra: pmc: Wait for powergate state to change

Jon Hunter
2016-01-15T09:06:37Z

On 14/01/16 14:01, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> On Fri, Dec 04, 2015 at 02:57:07PM +0000, Jon Hunter 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 macro has also been adding for checking the status of the powergate and
>
> "added"

Ok, thanks.

>> so update the tegra_powergate_is_powered() to use this macro as well.
>>
>> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
>> ---
>> arch/arm/mach-tegra/platsmp.c | 16 +++-------------
>> drivers/soc/tegra/pmc.c | 21 +++++++++++++++------
>> 2 files changed, 18 insertions(+), 19 deletions(-)
>>
>> diff --git a/arch/arm/mach-tegra/platsmp.c b/arch/arm/mach-tegra/platsmp.c
>> index b45086666648..40cb761e7c95 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. */
>
> I vaguely remember this being very brittle. I assume you've tested this
> extensively and made sure it doesn't regress?

I have boot tested several times, but if you are concerned about this
secondary boot failing specifically, I could setup a test over the
weekend to boot test say 1000 iterations for all boards.

>> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
>> index fdd1a8d0940f..f94d970089ce 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>
>> @@ -101,6 +102,8 @@
>>
>> #define GPU_RG_CNTRL 0x2d4
>>
>> +#define PMC_PWRGATE_STATE(status, id) ((status & BIT(id)) != 0)
>> +
>
> This looks suspiciously like a register or register field definition.
> Maybe turn this into a static inline function, such as:
>
> static inline bool tegra_powergate_state(u32 status, int id)
> {
> return (status & BIT(id)) != 0;
> }
>
> ?

Ok.

>> struct tegra_pmc_soc {
>> unsigned int num_powergates;
>> const char *const *powergates;
>> @@ -181,22 +184,27 @@ static void tegra_pmc_writel(u32 value, unsigned long offset)
>> */
>> static int tegra_powergate_set(int id, bool new_state)
>> {
>> - bool status;
>> + u32 status;
>> + int err = 0;
>
> Initialization to 0 doesn't seem necessary here.

Yes, ok.

Cheers
Jon