sensor creator init split#2445
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sysinit stage for flash map is currently 2. It leaves very little space for additional code that should be executed before flash_map is initialized but after OS is created. If some package initialization is to be executed before flash_map, setting its stage to 1 is risky since OS is stage 1.
This splits existing function sensor_dev_create(). All the devices are still created in this function but code that actually accessed them is moved to separate function sensor_dev_init(). This is really needed in case when SPI flash is used in flash map. Flash map is initialized in early stage. If by that time devices that are connected to the same SPI bus are not created yet, GPIO that is used for chip selection may be perceived as active since it was not configured yet. In such case two devices (SPI flash and some SPI sensor) could try to respond at the same time and SPI flash command responses can be corrupted.
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vrahane
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Dec 18, 2020
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Looks good. That was a really good catch. The config for the sensors should have taken care of this situation as it would configure the spi accordingly but this seems like a cleaner solution.
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This solves the problem of sensor_creator usage along with SPI flash that is present in flash map.
If BSP uses SPI flash and sensor creator with SPI devices that are connected to the same
SPI bus as flash, not initializing chip select pin for those other devices may lead to wrong
reads from flash.
It happens when uninitialized yet GPIO is still perceived by sensor as active and sensor responds
to requests that should be answered by flash.
This adds sensor_dev_init() that has initialization code taken from sensor_dev_create().
Thai also changes flash_map initialization stage to accommodate for other initialization that
could be needed before flash_map can be initialized.