RE: [PATCH 16/17] OMAP3: PM: Write voltage and clock setup times dynamically in idle loop

Tero.Kristo
2009-10-21T09:56:03Z

>-----Original Message-----
>From: ext Kevin Hilman [mailto:khilman@deeprootsystems.com]
>Sent: 20 October, 2009 20:48
>To: Kristo Tero (Nokia-D/Tampere)
>Cc: linux-omap@vger.kernel.org
>Subject: Re: [PATCH 16/17] OMAP3: PM: Write voltage and clock
>setup times dynamically in idle loop
>
>Tero Kristo <tero.kristo@nokia.com> writes:
>
>> From: Tero Kristo <tero.kristo@nokia.com>
>>
>> It is suggested by TI (SWPA152 February 2009) to write clksetup,
>> voltsetup_time1, voltsetup_time2, voltsetup2 dynamically in
>idle loop.
>
>Can you summarize the reasons why?

Basically this optimizes the clksetup / voltsetup times according to the sleep mode. Currently the settings are too high in both retention and off-mode, because the hardware appears to use for example VOLTSETUP2 even if we are not in off-mode, adding extra delay to wakeup. Also, CLKSETUP is too high for retention mode because oscillator is not actually shut-off here.

However, now that I think about it, it might be better to change this in a way that it is user configurable whether we want to change the settings or not, maybe add new items in to the prm_setup struct for alternate settings for ret / off and only use these if available. Some boards might actually switch oscillator off in retention mode which would require higher setup time.

>
>> Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
>> ---
>> arch/arm/mach-omap2/pm34xx.c | 36
>+++++++++++++++++++++++++-----------
>> 1 files changed, 25 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/arm/mach-omap2/pm34xx.c
>b/arch/arm/mach-omap2/pm34xx.c
>> index f492142..ae83121 100644
>> --- a/arch/arm/mach-omap2/pm34xx.c
>> +++ b/arch/arm/mach-omap2/pm34xx.c
>> @@ -575,6 +575,30 @@ void omap_sram_idle(void)
>> if (regset_save_on_suspend)
>> pm_dbg_regset_save(1);
>>
>> + /* Write voltage setup times which are changed dynamically */
>
>AFAICT, we only set these values at init time and they are never
>changed. Are there some forthcoming patches that change these
>dynamically?

Following bit of the code actually changes them dynamically, you can see that e.g. CLKSETUP time is either prm_setup.clksetup or 0x1 depending on the sleep mode. But as previously said, I think these should probably be added as new items to the prm_setup struct.

>
>Kevin
>
>> + if (core_next_state == PWRDM_POWER_OFF) {
>> + prm_write_mod_reg(0, OMAP3430_GR_MOD,
>> + OMAP3_PRM_VOLTSETUP1_OFFSET);
>> + prm_write_mod_reg(prm_setup.voltsetup2, OMAP3430_GR_MOD,
>> + OMAP3_PRM_VOLTSETUP2_OFFSET);
>> + prm_write_mod_reg(prm_setup.clksetup, OMAP3430_GR_MOD,
>> + OMAP3_PRM_CLKSETUP_OFFSET);
>> + } else {
>> + prm_write_mod_reg((prm_setup.voltsetup_time2 <<
>> + OMAP3430_SETUP_TIME2_SHIFT) |
>> + (prm_setup.voltsetup_time1 <<
>> + OMAP3430_SETUP_TIME1_SHIFT),
>> + OMAP3430_GR_MOD,
>OMAP3_PRM_VOLTSETUP1_OFFSET);
>> + prm_write_mod_reg(0, OMAP3430_GR_MOD,
>> + OMAP3_PRM_VOLTSETUP2_OFFSET);
>> + /*
>> + * Use static 1 as only HF_CLKOUT is turned off.
>> + * Value taken from application note SWPA152
>> + */
>> + prm_write_mod_reg(0x1, OMAP3430_GR_MOD,
>> + OMAP3_PRM_CLKSETUP_OFFSET);
>> + }
>> +
>> /*
>> * omap3_arm_context is the location where ARM registers
>> * get saved. The restore path then reads from this
>> @@ -1379,19 +1403,9 @@ static void __init configure_vc(void)
>> OMAP3430_GR_MOD,
>> OMAP3_PRM_VC_I2C_CFG_OFFSET);
>>
>> - /* Write setup times */
>> - prm_write_mod_reg(prm_setup.clksetup, OMAP3430_GR_MOD,
>> - OMAP3_PRM_CLKSETUP_OFFSET);
>> - prm_write_mod_reg((prm_setup.voltsetup_time2 <<
>> - OMAP3430_SETUP_TIME2_SHIFT) |
>> - (prm_setup.voltsetup_time1 <<
>> - OMAP3430_SETUP_TIME1_SHIFT),
>> - OMAP3430_GR_MOD, OMAP3_PRM_VOLTSETUP1_OFFSET);
>> -
>> + /* Write static setup times */
>> prm_write_mod_reg(prm_setup.voltoffset, OMAP3430_GR_MOD,
>> OMAP3_PRM_VOLTOFFSET_OFFSET);
>> - prm_write_mod_reg(prm_setup.voltsetup2, OMAP3430_GR_MOD,
>> - OMAP3_PRM_VOLTSETUP2_OFFSET);
>>
>> pm_dbg_regset_init(1);
>> pm_dbg_regset_init(2);
>> --
>> 1.5.4.3
>>
>> --
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