[ Upstream commit 9d32497361ff89d2fc8306407de6f04b2bfb2836 ] Ensure the ordering of the fifo write and the update of the write index, so that the index is not updated before the data has landed in the fifo. Acked-By: Chris Lew <clew@codeaurora.org> Reported-by: Arun Kumar Neelakantam <aneela@codeaurora.org> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> Signed-off-by: Lee Jones <lee.jones@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>