libpayload: ipq808x: stale interrupt shall not be cleared unconditionally

The serial driver hangs in cases when FIFO has more than single word to be
processed. Easiest way to reproduce is to paste a string of greater than 4
characters in cli.

Clearing the RXSTALE interrupt without draining all the characters from FIFO
leads to the issue as the driver is dependent on msm_boot_uart_dm_read
function to reinitialize for next transfer.

Logically the driver is organized in such a manner that next transfer never
gets initiated till rx_data_read < total_rx_data. Clearing the RXSTALE without
consideration of total number of characters (or words) unprocessed makes the
msm_boot_uart_dm_read to return on the first if conditional. Thus the driver is
stuck forever.

A quick fix is to avoid clearing the stale interrupt. Reset is handled whenever
a new transfer is initialized in msm_boot_uart_dm_init_rx_transfer.

BUG=chrome-os-partner:29542
TEST=manual
	-Paste a string greater than 4 characters in cli.

Original-Change-Id: I016afb01a77cd14764f0176f6bf144fb29796c2f
Original-Signed-off-by: Yogesh Lal <ylal@codeaurora.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/209512
Original-Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Commit-Queue: Vadim Bendebury <vbendeb@chromium.org>
Original-Tested-by: Vadim Bendebury <vbendeb@chromium.org>
(cherry picked from commit 61528884ad2c0a8e146054bbfeb01a3bc73b9692)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I936af5daa52a25f62133bdf9fb44f0b68cf34e88
Reviewed-on: http://review.coreboot.org/8667
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

0 files changed, 0 insertions, 0 deletions