From: kernel@martin.sperl.org To: Rob Herring <robh+dt@kernel.org>, Stephen Warren <swarren@wwwdotorg.org>, Lee Jones <lee@kernel.org>, Eric Anholt <eric@anholt.net>, Michael Turquette <mturquette@baylibre.com>, Stephen Boyd <sboyd@codeaurora.org>, Remi Pommarel <repk@triplefau.lt>, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org Cc: Martin Sperl <kernel@martin.sperl.org> Subject: [RFC 6/9] clk: bcm2835: allow to define a minimum fractional divider in DT Date: Tue, 19 Jan 2016 14:51:37 +0000 [thread overview] Message-ID: <1453215100-2382-7-git-send-email-kernel@martin.sperl.org> (raw) In-Reply-To: <1453215100-2382-1-git-send-email-kernel@martin.sperl.org> From: Martin Sperl <kernel@martin.sperl.org> Allow to define a minimum fractional divider to use in the devicetree. This is primarily used to reduce clock-jitter introduced by the fractional/MASH divider. Signed-off-by: Martin Sperl <kernel@martin.sperl.org> --- drivers/clk/bcm/clk-bcm2835.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c index e5313ba..7048ca5 100644 --- a/drivers/clk/bcm/clk-bcm2835.c +++ b/drivers/clk/bcm/clk-bcm2835.c @@ -711,6 +711,8 @@ struct bcm2835_clock_data { u32 int_bits; /* Number of fractional bits in the divider */ u32 frac_bits; + /* the minimum divider to allow when fractional */ + u32 min_frac_div; /* the mash value to use - see CM_MASH */ enum bcm2835_clock_mash_type mash; bool mash_forced; @@ -1709,13 +1711,21 @@ static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw, struct bcm2835_rates *rates, size_t rate_cnt) { + struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw); + const struct bcm2835_clock_data *data = clock->data; struct bcm2835_rates *best = NULL; size_t i; /* find best matching */ for (i = 0; i < rate_cnt; i++) { + /* do not look at anything above the requested rate */ if (rates[i].rate > req->rate) continue; + /* if we have a divider that is not "safe", then ignore */ + if (divmash_get_divf(rates[i].dmash) && + (rates[i].div < data->min_frac_div)) + continue; + /* if we are the first */ if (!best) { best = &rates[i]; continue; @@ -2094,6 +2104,10 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of( break; } } + /* add support for min fractional divider */ + err = of_property_read_u32(nc, "brcm,min-fract-div", &value); + if (!err) + data->min_frac_div = value << CM_DIV_FRAC_BITS; /* and return the result */ return data; -- 1.7.10.4
WARNING: multiple messages have this Message-ID (diff)
From: kernel@martin.sperl.org (kernel at martin.sperl.org) To: linux-arm-kernel@lists.infradead.org Subject: [RFC 6/9] clk: bcm2835: allow to define a minimum fractional divider in DT Date: Tue, 19 Jan 2016 14:51:37 +0000 [thread overview] Message-ID: <1453215100-2382-7-git-send-email-kernel@martin.sperl.org> (raw) In-Reply-To: <1453215100-2382-1-git-send-email-kernel@martin.sperl.org> From: Martin Sperl <kernel@martin.sperl.org> Allow to define a minimum fractional divider to use in the devicetree. This is primarily used to reduce clock-jitter introduced by the fractional/MASH divider. Signed-off-by: Martin Sperl <kernel@martin.sperl.org> --- drivers/clk/bcm/clk-bcm2835.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c index e5313ba..7048ca5 100644 --- a/drivers/clk/bcm/clk-bcm2835.c +++ b/drivers/clk/bcm/clk-bcm2835.c @@ -711,6 +711,8 @@ struct bcm2835_clock_data { u32 int_bits; /* Number of fractional bits in the divider */ u32 frac_bits; + /* the minimum divider to allow when fractional */ + u32 min_frac_div; /* the mash value to use - see CM_MASH */ enum bcm2835_clock_mash_type mash; bool mash_forced; @@ -1709,13 +1711,21 @@ static int bcm2835_clock_determine_closest_rate(struct clk_hw *hw, struct bcm2835_rates *rates, size_t rate_cnt) { + struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw); + const struct bcm2835_clock_data *data = clock->data; struct bcm2835_rates *best = NULL; size_t i; /* find best matching */ for (i = 0; i < rate_cnt; i++) { + /* do not look@anything above the requested rate */ if (rates[i].rate > req->rate) continue; + /* if we have a divider that is not "safe", then ignore */ + if (divmash_get_divf(rates[i].dmash) && + (rates[i].div < data->min_frac_div)) + continue; + /* if we are the first */ if (!best) { best = &rates[i]; continue; @@ -2094,6 +2104,10 @@ static const struct bcm2835_clock_data *bcm2835_register_clock_of( break; } } + /* add support for min fractional divider */ + err = of_property_read_u32(nc, "brcm,min-fract-div", &value); + if (!err) + data->min_frac_div = value << CM_DIV_FRAC_BITS; /* and return the result */ return data; -- 1.7.10.4
next prev parent reply other threads:[~2016-01-19 14:51 UTC|newest] Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-01-19 14:51 [RFC 0/9] Allow modifications of specific clocks via DT and more kernel-TqfNSX0MhmxHKSADF0wUEw 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` kernel 2016-01-19 14:51 ` [RFC 2/9] clk: bcm2835: add support for parent selection in DT kernel 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-21 8:26 ` Sascha Hauer 2016-01-21 8:26 ` Sascha Hauer 2016-02-08 13:30 ` Martin Sperl 2016-02-08 13:30 ` Martin Sperl 2016-01-19 14:51 ` [RFC 3/9] clk: bcm2835: add ability to control mash level via device-tree kernel 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` [RFC 4/9] clk: bcm2835: reorganize bcm2835_clock_determine_rate kernel 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` [RFC 5/9] clk: bcm2835: prefer clocks that use integer dividers kernel 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` kernel [this message] 2016-01-19 14:51 ` [RFC 6/9] clk: bcm2835: allow to define a minimum fractional divider in DT kernel at martin.sperl.org [not found] ` <1453215100-2382-1-git-send-email-kernel-TqfNSX0MhmxHKSADF0wUEw@public.gmane.org> 2016-01-19 14:51 ` [RFC 1/9] clk: bcm2835: add basic device tree support for per clock settings kernel-TqfNSX0MhmxHKSADF0wUEw 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` kernel 2016-01-19 14:51 ` [RFC 7/9] clk: bcm2835: allow clock choosing mechanims to be selected in DT kernel-TqfNSX0MhmxHKSADF0wUEw 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` kernel 2016-01-19 14:51 ` [RFC 8/9] dt-bindings: bcm2835: document optional per clock dt-nodes kernel 2016-01-19 14:51 ` kernel at martin.sperl.org 2016-01-19 14:51 ` [RFC 9/9] clk: bcm2835: expose raw clock-registers via debugfs kernel 2016-01-19 14:51 ` kernel at martin.sperl.org
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