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libpayload: ipq808x: stale interrupt shall not be cleared unconditionally

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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.

Change-Id: I016afb01a77cd14764f0176f6bf144fb29796c2f
Signed-off-by: Yogesh Lal <ylal@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/209512
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Commit-Queue: Vadim Bendebury <vbendeb@chromium.org>
Tested-by: Vadim Bendebury <vbendeb@chromium.org>
This commit is contained in:
Yogesh Lal 2014-06-27 12:07:51 +05:30 • committed by chrome-internal-fetch
commit 61528884ad
1 changed files with 0 additions and 3 deletions
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3
payloads/libpayload/drivers/serial/ipq806x.c
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@ -152,9 +152,6 @@ static unsigned msm_boot_uart_dm_read(void)
return IPQ_UART_DM_E_RX_NOT_READY;
}
/* Clear stale event. */
writel(IPQ_UART_DM_CMD_RES_STALE_INT, IPQ_UART_DM_CR(base));
/* Read UART_DM_RX_TOTAL_SNAP for actual number of bytes received */
if (total_rx_data == 0)
total_rx_data = readl(IPQ_UART_DM_RX_TOTAL_SNAP(base));