From mboxrd@z Thu Jan 1 00:00:00 1970 From: kernel@martin.sperl.org Subject: [RFC 5/9] clk: bcm2835: prefer clocks that use integer dividers Date: Tue, 19 Jan 2016 14:51:36 +0000 Message-ID: <1453215100-2382-6-git-send-email-kernel@martin.sperl.org> References: <1453215100-2382-1-git-send-email-kernel@martin.sperl.org> Return-path: In-Reply-To: <1453215100-2382-1-git-send-email-kernel@martin.sperl.org> Sender: linux-clk-owner@vger.kernel.org To: Rob Herring , Stephen Warren , Lee Jones , Eric Anholt , Michael Turquette , Stephen Boyd , Remi Pommarel , devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org Cc: Martin Sperl List-Id: devicetree@vger.kernel.org From: Martin Sperl To reduce possible jitter prefer integer dividers over fractional dividers. Signed-off-by: Martin Sperl --- drivers/clk/bcm/clk-bcm2835.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c index f1ab525..e5313ba 100644 --- a/drivers/clk/bcm/clk-bcm2835.c +++ b/drivers/clk/bcm/clk-bcm2835.c @@ -1686,6 +1686,24 @@ static int bcm2835_clock_determine_rate_set(struct clk_rate_request *req, return 0; } +static int bcm2835_clock_determine_integer_rate(struct clk_hw *hw, + struct clk_rate_request *req, + struct bcm2835_rates *rates, + size_t rate_cnt) +{ + size_t i; + + /* find first matching */ + for (i = 0; i < rate_cnt; i++) { + if (!divmash_get_divf(rates[i].dmash)) + return bcm2835_clock_determine_rate_set(req, + &rates[i]); + } + + /* nothing found */ + return -EINVAL; +} + static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw, struct clk_rate_request *req, struct bcm2835_rates *rates, @@ -1729,6 +1747,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, struct bcm2835_rates rates[BIT(CM_SRC_BITS)]; size_t i, rate_cnt = 0; divmash dm; + int err; /* fill in rates */ for (i = 0; i < clk_hw_get_num_parents(hw); ++i) { @@ -1745,7 +1764,12 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw, rate_cnt++; } - /* choose the "closest" one */ + /* find integer rates with preference */ + err = bcm2835_clock_determine_integer_rate(hw, req, rates, rate_cnt); + if (!err) + return 0; + + /* otherwise choose the "closest" one */ return bcm2835_clock_determine_closest_rate(hw, req, rates, rate_cnt); } -- 1.7.10.4