From: Huang Shijie <b32955@freescale.com>
Date: Fri, 11 Oct 2013 10:30:58 +0000 (+0800)
Subject: serial: imx: implement the flush_buffer hook
X-Git-Tag: omap-for-v3.13/fixes-for-merge-window-take2~63^2~29
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eb56b7edae6ba2bfd3a07e59ea82195e2c1c28ec;p=pandora-kernel.git

serial: imx: implement the flush_buffer hook

The current driver does not implement the flush_buffer hook for
uart_ops. When we enable the DMA for the driver, and test it with Bluetooth,
we may meet the following bug for TX:

    [1] User application may call the flush operation at any time.
        The uart_flush_buffer() calls the uart_circ_clear() to set
        the xmit->head and xmit->tail with 0.

    [2] The TX DMA callback can be called at any time too.
        The dma_tx_call() will update the xmit->tail.

    If [2] occurs just after the [1], we will get the wrong xmit->tail.

This patch implements the flush_buffer hook to fix this issue.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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