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cdd5c206cd
STM32 has a single-byte mailbox for UART I/O. When the core clock
runs at 16Mhz we can service interrupts fast enough to handle 115200
baud input, but when we drop to 1MHz we drop characters. Using DMA to
receive input solves this problem.
The STM32 DMA engine can only generate interrupts when the transfer is
half-done / all-done, so we need to poll the DMA receive-head-pointer
to see if individual characters have been received. Do this in the
tick task (every 250ms). When a character is received, poll more
quickly for a bit (5 times before the next tick) so the input console
is more responsive to typing.
BUG=chrome-os-partner:20485
BRANCH=none
TEST=Console is responsive to debug commands. For example, help -> prints help
apshutdown -> shuts down AP
arrow keys -> move cursor and scroll through command history
Ctrl+Q, help, wait a second, Ctrl+S -> help output printed after Ctrl+S
Then in chip/stm32/config_chip.h, comment out #define CONFIG_UART_RX_DMA
and rebuild/reflash the EC. When the AP is up, the console works normally
but after 'apshutdown', the EC drops to 1MHz core clock, and the arrow
keys don't work. (This step confirms that adding DMA support did not
change the behavior of systems where CONFIG_UART_RX_DMA is not defined.)
Change-Id: I199448354824bd747c7b290ea7fd5ccf354c11bb
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/169406
Reviewed-by: Simon Glass <sjg@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.