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ARM: mxs: fix VDDD brownout setting

PATCH New Michael Heimpold 3 participants 5 messages Nov 15, 2015 – Dec 1, 2015

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Arm (32-bit) Arm i.MX and Layerscape
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Michael Heimpold

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#0 lore raw

PATCH 1/1 ARM: mxs: fix VDDD brownout setting

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 <[email protected]>
Cc Marek Vasut <[email protected]>
Cc Otavio Salvador <[email protected]>
Cc Fabio Estevam <[email protected]>
---
 arch/arm/cpu/arm926ejs/mxs/spl_power_init.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
arch/arm/cpu/arm926ejs/mxs/spl_power_init.c +2 -2
index 42f3df2..1972de8 100644
@@ -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);
Signature · 1 line
2.5.0
#1 lore raw

PATCH 1/1 ARM: mxs: fix VDDD brownout setting

Quoted 19 lines · Michael Heimpold

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].

Quoted 7 lines

So lets use this value as desired BO value (which is also the same as FSL bootlets use).

Signed-off-by Michael Heimpold <[email protected]>
Cc Marek Vasut <[email protected]>
Cc Otavio Salvador <[email protected]>
Cc Fabio Estevam <[email protected]>

Uh, nice find. How did you find it?

Acked-by Marek Vasut <[email protected]>

Best regards,
Marek Vasut

author
#2 lore raw

PATCH 1/1 ARM: mxs: fix VDDD brownout setting

Hi Marek,

Am Monday 16 November 2015, 12:01:36 schrieben Sie:

Quoted 24 lines · Michael Heimpold
Quoted 23 lines

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).

Quoted 6 lines
Quoted 4 lines
Signed-off-by Michael Heimpold <[email protected]>
Cc Marek Vasut <[email protected]>
Cc Otavio Salvador <[email protected]>
Cc Fabio Estevam <[email protected]>

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

Quoted 5 lines
Acked-by Marek Vasut <[email protected]>

Best regards,
Marek Vasut

#3 lore raw

PATCH 1/1 ARM: mxs: fix VDDD brownout setting

Quoted 1 line · Michael Heimpold

Hi Marek,

Hi!

Quoted 30 lines

Am Monday 16 November 2015, 12:01:36 schrieben Sie:

Quoted 29 lines · Michael Heimpold
Quoted 27 lines

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 <[email protected]>
Cc Marek Vasut <[email protected]>
Cc Otavio Salvador <[email protected]>
Cc Fabio Estevam <[email protected]>
Quoted 6 lines
Quoted 1 line

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

#4 lore raw

PATCH 1/1 ARM: mxs: fix VDDD brownout setting

In reply to Michael Heimpold
Quoted 19 lines · Michael Heimpold

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].

Quoted 8 lines

So lets use this value as desired BO value (which is also the same as FSL bootlets use).

Signed-off-by Michael Heimpold <[email protected]>
Cc Marek Vasut <[email protected]>
Cc Otavio Salvador <[email protected]>
Cc Fabio Estevam <[email protected]>

---

Applied to u-boot-imx, thanks!

Best regards,
Stefano Babic

Signature · 5 lines
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