From f59de563358eb9351b7f8f0ba2d3be2ebb70b93d Mon Sep 17 00:00:00 2001 From: Chris Brandt Date: Tue, 14 Feb 2017 11:08:05 -0500 Subject: [PATCH] clk: renesas: mstp: ensure register writes complete When there is no status bit, it is possible for the clock enable/disable operation to have not completed by the time the driver code resumes execution. This is due to the fact that write operations are sometimes queued and delayed internally. Doing a read ensures the write operations has completed. Fixes: b6face404f38 ("ARM: shmobile: r7s72100: add essential clock nodes to dtsi") Signed-off-by: Chris Brandt Reviewed-by: Geert Uytterhoeven Signed-off-by: Stephen Boyd --- drivers/clk/renesas/clk-mstp.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/clk/renesas/clk-mstp.c b/drivers/clk/renesas/clk-mstp.c index 3ce819c..4067216 100644 --- a/drivers/clk/renesas/clk-mstp.c +++ b/drivers/clk/renesas/clk-mstp.c @@ -91,6 +91,12 @@ static int cpg_mstp_clock_endisable(struct clk_hw *hw, bool enable) value |= bitmask; cpg_mstp_write(group, value, group->smstpcr); + if (!group->mstpsr) { + /* dummy read to ensure write has completed */ + cpg_mstp_read(group, group->smstpcr); + barrier_data(group->smstpcr); + } + spin_unlock_irqrestore(&group->lock, flags); if (!enable || !group->mstpsr) -- 2.7.4