How to keep DM37x GPIO_162 high during off-mode

I'm working with a 3.0.8 kernel in Android ICS and have run into a problem using wl12xx bluetooth after a suspend/resume cycle.

GPIO_162 in this design is connected to the BT_EN pin of the wl12xx and needs to be held high to keep the bluetooth core from resetting while the DM37x goes into off mode.

I've tried muxing the pin using OMAP_PIN_OUTPUT | OMAP_PIN_OFF_OUTPUT_HIGH, but the pin goes low when the chip goes into off mode. If I disable off mode via "echo 0 > /sys/kernel/debug/pm_debug/enable_off_mode" the pin remains high while the chip goes into retention and the bluetooth core works after resume.

Any ideas why GPIO_162 would go low during suspend to off mode?

Quoted 7 lines · Peter Barada

I'm working with a 3.0.8 kernel in Android ICS and have run into a problem using wl12xx bluetooth after a suspend/resume cycle.

GPIO_162 in this design is connected to the BT_EN pin of the wl12xx and needs to be held high to keep the bluetooth core from resetting while the DM37x goes into off mode.

Quoted 7 lines

I've tried muxing the pin using OMAP_PIN_OUTPUT | OMAP_PIN_OFF_OUTPUT_HIGH, but the pin goes low when the chip goes into off mode. If I disable off mode via "echo 0 > /sys/kernel/debug/pm_debug/enable_off_mode" the pin remains high while the chip goes into retention and the bluetooth core works after resume.

Any ideas why GPIO_162 would go low during suspend to off mode?

Unless the GPIO is in a GPIO bank that's connected to the WKUP power domain, the GPIO bank context will be lost. So there's a short period where the GPIO bank is in an uninitialized state between waking from off-idle and before the context to the GPIO bank gets restored in omap_gpio_runtime_resume().

If there's a pull on the line, the period is long enough to change the line.

Unless the TI people know some magic tricks that I'm not aware of, there's no way around it, except to use external pulls to keep the GPIO line in desired state, or move the GPIO somewhere else, like TWL.

Quoted 21 lines · Tony Lindgren

Quoted 7 lines · Peter Barada

I'm working with a 3.0.8 kernel in Android ICS and have run into a problem using wl12xx bluetooth after a suspend/resume cycle.

GPIO_162 in this design is connected to the BT_EN pin of the wl12xx and needs to be held high to keep the bluetooth core from resetting while the DM37x goes into off mode.

Quoted 7 lines

I've tried muxing the pin using OMAP_PIN_OUTPUT | OMAP_PIN_OFF_OUTPUT_HIGH, but the pin goes low when the chip goes into off mode. If I disable off mode via "echo 0 > /sys/kernel/debug/pm_debug/enable_off_mode" the pin remains high while the chip goes into retention and the bluetooth core works after resume.

Any ideas why GPIO_162 would go low during suspend to off mode?

Unless the GPIO is in a GPIO bank that's connected to the WKUP power domain, the GPIO bank context will be lost. So there's a short period where the GPIO bank is in an uninitialized state between waking from off-idle and before the context to the GPIO bank gets restored in omap_gpio_runtime_resume().

Quoted 9 lines

If there's a pull on the line, the period is long enough to change the line.

Unless the TI people know some magic tricks that I'm not aware of, there's no way around it, except to use external pulls to keep the GPIO line in desired state, or move the GPIO somewhere else, like TWL.

Unfortunately the hardware doesn't have an external pullup, and re-spinning it to route BT_EN to a GPIO pin that's in the WKUP domain isn't an option at this time...

Unless there's some TI-magic to keep GPIO_162 high during OFF mode I'll have to solve this the hard way by reinitializing the BT/GPS core during resume using deferred work. Unfirtuantely I don't have a clear understanding of the userspace interaction to know if this is doable.

Mechanically it doesn't look too difficult to use the guts of st_register/st_kim_start to reinitialize the GT/GPS core and download its firmware, but the userspace interactions (and the time it takes to load the firmware) is what makes coming up with a good solution difficult.

Any suggestions on how to approach solving this are most appreciated!

Hi Peter,

Quoted 42 lines · Peter Barada

Quoted 23 lines · Tony Lindgren

Quoted 8 lines · Peter Barada

I'm working with a 3.0.8 kernel in Android ICS and have run into a problem using wl12xx bluetooth after a suspend/resume cycle.

GPIO_162 in this design is connected to the BT_EN pin of the wl12xx and
needs to be held high to keep the bluetooth core from resetting while the DM37x goes into off mode.

Quoted 8 lines

I've tried muxing the pin using OMAP_PIN_OUTPUT | OMAP_PIN_OFF_OUTPUT_HIGH, but the pin goes low when the chip goes into off mode. If I disable off mode via "echo 0 > /sys/kernel/debug/pm_debug/enable_off_mode" the pin remains high while the chip goes into retention and the bluetooth core works after resume.

Any ideas why GPIO_162 would go low during suspend to off mode?

Unless the GPIO is in a GPIO bank that's connected to the WKUP power domain, the GPIO bank context will be lost. So there's a short period where the GPIO bank is in an uninitialized state between waking from off-idle and before the context to the GPIO bank gets restored in omap_gpio_runtime_resume().

Quoted 9 lines

If there's a pull on the line, the period is long enough to change the line.

Unless the TI people know some magic tricks that I'm not aware of, there's no way around it, except to use external pulls to keep the GPIO line in desired state, or move the GPIO somewhere else, like TWL.

Unfortunately the hardware doesn't have an external pullup, and re-spinning it to route BT_EN to a GPIO pin that's in the WKUP domain isn't an option at this time...

Unless there's some TI-magic to keep GPIO_162 high during OFF mode I'll have to solve this the hard way by reinitializing the BT/GPS core during resume using deferred work. Unfirtuantely I don't have a clear understanding of the userspace interaction to know if this is doable.

Quoted 8 lines

Mechanically it doesn't look too difficult to use the guts of st_register/st_kim_start to reinitialize the GT/GPS core and download its firmware, but the userspace interactions (and the time it takes to load the firmware) is what makes coming up with a good solution difficult.

Any suggestions on how to approach solving this are most appreciated!

The recommended way is to configure it as INPUT + PULL_UP and don't use OFFMODE feature if the 1 value is needed on port during off-mode.

You need to check if you have valid pin-cfg right before call to omap4_enter_lowpower() ->omap4_cpu_suspend(cpu, save_state);

I recommend you to ask you questions here:
http://e2e.ti.com/support/omap/default.aspx

Regards,
- grygorii