mirror of
https://github.com/Telecominfraproject/OpenCellular.git
synced 2025-12-29 18:11:05 +00:00
bad6201834
Currently, the STM32L I2C driver queues the stop condition, but
doesn't actually wait for it to take effect before returning. If
another back-to-back transfer is started, this may attempt to send a
start condition before the stop condition completes. If this happens
after a slave read, this can look to the slave like just another pulse
on SCL, causing it to clock out another bit - potentially driving SDA
low and hanging the bus.
Instead, wait for the bus to go idle, then wait another clock period
(10 us) to give the slaves plenty of time to detect bus-idle before
the next start condition.
BUG=chrome-os-partner:22093
BRANCH=pit
TEST=repeatedly run the battery i2c command from the EC console while
running 'ectool i2cxfer 0 0x48 1' from a root shell. Should not hang
the I2C bus.
Change-Id: I5e65ee242537dbc801fba4ae57847a5af5104186
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/66997
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Commit-Queue: Douglas Anderson <dianders@chromium.org>
In the most general case, the flash layout looks something like this: +---------------------+ | Reserved for EC use | +---------------------+ +---------------------+ | Vblock B | +---------------------+ | RW firmware B | +---------------------+ +---------------------+ | Vblock A | +---------------------+ | RW firmware A | +---------------------+ +---------------------+ | FMAP | +---------------------+ | Public root key | +---------------------+ | Read-only firmware | +---------------------+ BIOS firmware (and kernel) put the vblock info at the start of each image where it's easy to find. The Blizzard EC expects the firmware vector table to come first, so we have to put the vblock at the end. This means we have to know where to look for it, but that's built into the FMAP and the RO firmware anyway, so that's not an issue. The RO firmware doesn't need a vblock of course, but it does need some reserved space for vboot-related things. Using SHA256/RSA4096, the vblock is 2468 bytes (0x9a4), while the public root key is 1064 bytes (0x428) and the current FMAP is 644 bytes (0x284). If we reserve 4K at the top of each FW image, that should give us plenty of room for vboot-related stuff.