linux-kernel - [PATCH 3.16.y-ckt 153/180] clk: qcom: fix RCG M/N counter configuration

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Date:	Thu,  7 May 2015 10:46:02 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Archit Taneja <architt@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 153/180] clk: qcom: fix RCG M/N counter configuration

3.16.7-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Archit Taneja <architt@...eaurora.org>

commit 0b21503dbbfa669dbd847b33578d4041513cddb2 upstream.

Currently, a RCG's M/N counter (used for fraction division) is
set to either 'bypass' (counter disabled) or 'dual edge' (counter
enabled) based on whether the corresponding rcg struct has a mnd
field specified and a non-zero N.

In the case where M and N are the same value, the M/N counter is
still enabled by code even though no division takes place.
Leaving the RCG in such a state can result in improper behavior.
This was observed with the DSI pixel clock RCG when M and N were
both set to 1.

Add an additional check (M != N) to enable the M/N counter only
when it's needed for fraction division.

Signed-off-by: Archit Taneja <architt@...eaurora.org>
Fixes: bcd61c0f535a (clk: qcom: Add support for root clock
generators (RCGs))
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/clk/qcom/clk-rcg2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
index cd185d5cc67a..9f5e0dfc3699 100644
--- a/drivers/clk/qcom/clk-rcg2.c
+++ b/drivers/clk/qcom/clk-rcg2.c
@@ -253,7 +253,7 @@ static int clk_rcg2_configure(struct clk_rcg2 *rcg, const struct freq_tbl *f)
 	mask |= CFG_SRC_SEL_MASK | CFG_MODE_MASK;
 	cfg = f->pre_div << CFG_SRC_DIV_SHIFT;
 	cfg |= rcg->parent_map[f->src] << CFG_SRC_SEL_SHIFT;
-	if (rcg->mnd_width && f->n)
+	if (rcg->mnd_width && f->n && (f->m != f->n))
 		cfg |= CFG_MODE_DUAL_EDGE;
 	ret = regmap_update_bits(rcg->clkr.regmap,
 			rcg->cmd_rcgr + CFG_REG, mask, cfg);
--
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