OK, I think I've found the problem with the power management. As it is stated in mt9p031 datasheet [3] p 59, a sequence involving [VAA,VAA_PIX,VDD_PLL], [VDD,VDD_IO], [Reset] and [Ext Clk] must be followed in order to properly power up or down the sensor. If we take a look to the LI-5M031 schematic[1] and Beagleboard xM schematic [2] we'll notice that voltages are connected as follows: [VDD] (1,8V) <--- V2.8 <--- CAM_CORE <--- VAUX3 TPS65950 [VDD_IO (VDDQ)] (1,8V) <--- V1.8 <--- CAM_IO <--- VAUX4 TPS65950 [VAA, VAA_PIX, VDD_PLL] (2,8V) <---| U6 |<-- V3.3VD <-- HUB_3V3 <--| U16 | enabled by USBHOST_PWR_EN <-- LEDA TPS65950 VAUX3 (VDD) and VAUX4 (VDD_IO) are fine, they are only used for powering our camera sensor. However, when it comes to the analog part (VAA, VAA_PIX...), it is got from HUB_3V3 which is also used for powering USB and ethernet. If we really want to activate/deactivate regulators that power mt9p031 we need to follow [3] p59. However, for that purpose we need to ensure that a call to regulator_enable() or regulator_disable() will really power on/off that supply, otherwise the sequence won't be matched and the chip will have problems. Beagleboard xM is a good example of platform where this happens since HUB_3V3 and thus (VAA, VAA_PIX, etc...) cannot be deactivated since it is being used by other devices. But there could be others. So, as a conclusion, and in order to unblock my work, my purpose for power management in mt9p031 would be the following: - Drop regulator handling as we cannot guarantee that power on sequence will be accomplished. - Keep on asserting/de-asserting reset which saves a lot of power. - Also activate/deactivate clock when necessary to save some power. I'm looking forward to read your comments on this. [1] https://www.leopardimaging.com/uploads/li-5m03_camera_board_v2.pdf [2] http://beagle.s3.amazonaws.com/design/xM-A3/BB-xM_Schematic_REVA3.pdf [3] http://www.aptina.com/products/image_sensors/mt9p031i12stc/ -- Javier Martin Vista Silicon S.L. CDTUC - FASE C - Oficina S-345 Avda de los Castros s/n 39005- Santander. Cantabria. Spain +34 942 25 32 60 www.vista-silicon.com -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
