| Message ID | 1447624032-16503-1-git-send-email-mhei@heimpold.de |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | Stefano Babic |
| Headers | show |
On Sunday, November 15, 2015 at 10:47:12 PM, Michael Heimpold wrote: > At the moment, the desired brownout is at 1.0V. However, > this setting cannot be realized by hardware since we have > only 3 bits to represent the voltage difference from the > target value. > > Target value is 1500 mV, brownout target is 1000 mV, > voltage steps are 25 mV. > > Register content calculation: > (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14 > > Register takes only 3 bits, that is 0x4. > > But 0x4 * 25 [mV] = 100 [mV], that means that actual > brownout level is 1500 [mV] - 100 [mV] = 1.4 V. > > Minimum possible BO level is > 1500 [mV] - 0x7 * 25 [mV] = 1315 [mV]. > > So lets use this value as desired BO value (which is > also the same as FSL bootlets use). > > Signed-off-by: Michael Heimpold <mhei@heimpold.de> > Cc: Marek Vasut <marex@denx.de> > Cc: Otavio Salvador <otavio@ossystems.com.br> > Cc: Fabio Estevam <fabio.estevam@freescale.com> Uh, nice find. How did you find it? Acked-by: Marek Vasut <marex@denx.de> Best regards, Marek Vasut
Hi Marek, Am Monday 16 November 2015, 12:01:36 schrieben Sie: > On Sunday, November 15, 2015 at 10:47:12 PM, Michael Heimpold wrote: > > At the moment, the desired brownout is at 1.0V. However, > > this setting cannot be realized by hardware since we have > > only 3 bits to represent the voltage difference from the > > target value. > > > > Target value is 1500 mV, brownout target is 1000 mV, > > voltage steps are 25 mV. > > > > Register content calculation: > > (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14 > > > > Register takes only 3 bits, that is 0x4. > > > > But 0x4 * 25 [mV] = 100 [mV], that means that actual > > brownout level is 1500 [mV] - 100 [mV] = 1.4 V. > > > > Minimum possible BO level is > > > > 1500 [mV] - 0x7 * 25 [mV] = 1315 [mV]. > > > > So lets use this value as desired BO value (which is > > also the same as FSL bootlets use). > > > > Signed-off-by: Michael Heimpold <mhei@heimpold.de> > > Cc: Marek Vasut <marex@denx.de> > > Cc: Otavio Salvador <otavio@ossystems.com.br> > > Cc: Fabio Estevam <fabio.estevam@freescale.com> > > Uh, nice find. How did you find it? I was investigating a boot stall with I2SE's Duckbill devices and since we're about to switch from FSL bootlets to U-Boot, I compared the register settings. Then I stumbled about the comment and wondered whether 1.0V BO level makes sense for 1.5V target voltage... Best regards, Michael Heimpold > > Acked-by: Marek Vasut <marex@denx.de> > > Best regards, > Marek Vasut
On Monday, November 16, 2015 at 08:47:38 PM, Michael Heimpold wrote: > Hi Marek, Hi! > Am Monday 16 November 2015, 12:01:36 schrieben Sie: > > On Sunday, November 15, 2015 at 10:47:12 PM, Michael Heimpold wrote: > > > At the moment, the desired brownout is at 1.0V. However, > > > this setting cannot be realized by hardware since we have > > > only 3 bits to represent the voltage difference from the > > > target value. > > > > > > Target value is 1500 mV, brownout target is 1000 mV, > > > voltage steps are 25 mV. > > > > > > Register content calculation: > > > (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14 > > > > > > Register takes only 3 bits, that is 0x4. > > > > > > But 0x4 * 25 [mV] = 100 [mV], that means that actual > > > brownout level is 1500 [mV] - 100 [mV] = 1.4 V. > > > > > > Minimum possible BO level is > > > > > > 1500 [mV] - 0x7 * 25 [mV] = 1315 [mV]. > > > > > > So lets use this value as desired BO value (which is > > > also the same as FSL bootlets use). > > > > > > Signed-off-by: Michael Heimpold <mhei@heimpold.de> > > > Cc: Marek Vasut <marex@denx.de> > > > Cc: Otavio Salvador <otavio@ossystems.com.br> > > > Cc: Fabio Estevam <fabio.estevam@freescale.com> > > > > Uh, nice find. How did you find it? > > I was investigating a boot stall with I2SE's Duckbill devices and since > we're about to switch from FSL bootlets to U-Boot, I compared the register > settings. Then I stumbled about the comment and wondered whether > 1.0V BO level makes sense for 1.5V target voltage... Heh, nice. Thanks! Best regards, Marek Vasut
On 15/11/2015 22:47, Michael Heimpold wrote: > At the moment, the desired brownout is at 1.0V. However, > this setting cannot be realized by hardware since we have > only 3 bits to represent the voltage difference from the > target value. > > Target value is 1500 mV, brownout target is 1000 mV, > voltage steps are 25 mV. > > Register content calculation: > (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14 > > Register takes only 3 bits, that is 0x4. > > But 0x4 * 25 [mV] = 100 [mV], that means that actual > brownout level is 1500 [mV] - 100 [mV] = 1.4 V. > > Minimum possible BO level is > 1500 [mV] - 0x7 * 25 [mV] = 1315 [mV]. > > So lets use this value as desired BO value (which is > also the same as FSL bootlets use). > > Signed-off-by: Michael Heimpold <mhei@heimpold.de> > Cc: Marek Vasut <marex@denx.de> > Cc: Otavio Salvador <otavio@ossystems.com.br> > Cc: Fabio Estevam <fabio.estevam@freescale.com> > --- Applied to u-boot-imx, thanks! Best regards, Stefano Babic
diff --git a/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c b/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c index 42f3df2..1972de8 100644 --- a/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c +++ b/arch/arm/cpu/arm926ejs/mxs/spl_power_init.c @@ -1221,8 +1221,8 @@ void mxs_power_init(void) debug("SPL: Setting VDDIO to 3V3 (brownout @ 3v15)\n"); mxs_power_set_vddx(&mxs_vddio_cfg, 3300, 3150); - debug("SPL: Setting VDDD to 1V5 (brownout @ 1v0)\n"); - mxs_power_set_vddx(&mxs_vddd_cfg, 1500, 1000); + debug("SPL: Setting VDDD to 1V5 (brownout @ 1v315)\n"); + mxs_power_set_vddx(&mxs_vddd_cfg, 1500, 1315); #ifdef CONFIG_MX23 debug("SPL: Setting mx23 VDDMEM to 2V5 (brownout @ 1v7)\n"); mxs_power_set_vddx(&mxs_vddmem_cfg, 2500, 1700);
At the moment, the desired brownout is at 1.0V. However, this setting cannot be realized by hardware since we have only 3 bits to represent the voltage difference from the target value. Target value is 1500 mV, brownout target is 1000 mV, voltage steps are 25 mV. Register content calculation: (1500 [mV] - 1000 [mV]) / 25 [mV] = 20 (decimal) = 0x14 Register takes only 3 bits, that is 0x4. But 0x4 * 25 [mV] = 100 [mV], that means that actual brownout level is 1500 [mV] - 100 [mV] = 1.4 V. Minimum possible BO level is 1500 [mV] - 0x7 * 25 [mV] = 1315 [mV]. So lets use this value as desired BO value (which is also the same as FSL bootlets use). Signed-off-by: Michael Heimpold <mhei@heimpold.de> Cc: Marek Vasut <marex@denx.de> Cc: Otavio Salvador <otavio@ossystems.com.br> Cc: Fabio Estevam <fabio.estevam@freescale.com> --- arch/arm/cpu/arm926ejs/mxs/spl_power_init.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)