From 2f7bf4af5c8177f6a27d9b67efdeb48f5bdbf821 Mon Sep 17 00:00:00 2001 From: Heiko Stübner Date: Tue, 24 Feb 2015 11:39:25 +0100 Subject: clk: divider: return real rate instead of divider value Commit bca9690b9426 ("clk: divider: Make generic for usage elsewhere") returned only the divider value for read-only dividers instead of the actual rate. Fixes: bca9690b9426 ("clk: divider: Make generic for usage elsewhere") Signed-off-by: Heiko Stuebner Reviewed-by: James Hogan Tested-by: James Hogan Acked-by: Stephen Boyd Signed-off-by: Michael Turquette --- drivers/clk/clk-divider.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/clk/clk-divider.c') diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index db7f8bce7467..eff8a862eb08 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -353,7 +353,7 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate, bestdiv = readl(divider->reg) >> divider->shift; bestdiv &= div_mask(divider->width); bestdiv = _get_div(divider->table, bestdiv, divider->flags); - return bestdiv; + return DIV_ROUND_UP(*prate, bestdiv); } return divider_round_rate(hw, rate, prate, divider->table, -- cgit v1.2.3 From da321133b53caf7889ed3ca1dabe4cc368db2604 Mon Sep 17 00:00:00 2001 From: Uwe Kleine-König Date: Sat, 21 Feb 2015 11:40:23 +0100 Subject: clk: divider: fix calculation of maximal parent rate for a given divider MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The rate provided at the output of a clk-divider is calculated as: DIV_ROUND_UP(parent_rate, div) since commit b11d282dbea2 (clk: divider: fix rate calculation for fractional rates). So to yield a rate not bigger than r parent_rate must be <= r * div. The effect of choosing a parent rate that is too big as was done before this patch results in wrongly ruling out good dividers. Note that this is not a complete fix as __clk_round_rate might return a value >= its 2nd parameter. Also for dividers with CLK_DIVIDER_ROUND_CLOSEST set the calculation is not accurate. But this fixes the test case by Sascha Hauer that uses a chain of three dividers under a fixed clock. Fixes: b11d282dbea2 (clk: divider: fix rate calculation for fractional rates) Suggested-by: Sascha Hauer Signed-off-by: Uwe Kleine-König Acked-by: Sascha Hauer Signed-off-by: Michael Turquette --- drivers/clk/clk-divider.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) (limited to 'drivers/clk/clk-divider.c') diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index eff8a862eb08..a1a029092c8d 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -144,12 +144,6 @@ static unsigned long clk_divider_recalc_rate(struct clk_hw *hw, divider->flags); } -/* - * The reverse of DIV_ROUND_UP: The maximum number which - * divided by m is r - */ -#define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1) - static bool _is_valid_table_div(const struct clk_div_table *table, unsigned int div) { @@ -313,7 +307,7 @@ static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate, return i; } parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), - MULT_ROUND_UP(rate, i)); + rate * i); now = DIV_ROUND_UP(parent_rate, i); if (_is_best_div(rate, now, best, flags)) { bestdiv = i; -- cgit v1.2.3 From 26bac95aa88c2b1747808c0b885abe7814c0165d Mon Sep 17 00:00:00 2001 From: Uwe Kleine-König Date: Sat, 21 Feb 2015 11:40:24 +0100 Subject: clk: divider: fix selection of divider when rounding to closest MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit It's an invalid approach to assume that among two divider values the one nearer the exact divider is the better one. Assume a parent rate of 1000 Hz, a divider with CLK_DIVIDER_POWER_OF_TWO and a target rate of 89 Hz. The exact divider is ~ 11.236 so 8 and 16 are the candidates to choose from yielding rates 125 Hz and 62.5 Hz respectivly. While 8 is nearer to 11.236 than 16 is, the latter is still the better divider as 62.5 is nearer to 89 than 125 is. Fixes: 774b514390b1 (clk: divider: Add round to closest divider) Signed-off-by: Uwe Kleine-König Acked-by: Sascha Hauer Acked-by: Maxime Coquelin Signed-off-by: Michael Turquette --- drivers/clk/clk-divider.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'drivers/clk/clk-divider.c') diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index a1a029092c8d..78b2e656ff6a 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -220,6 +220,7 @@ static int _div_round_closest(const struct clk_div_table *table, unsigned long flags) { int up, down, div; + unsigned long up_rate, down_rate; up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate); @@ -231,7 +232,10 @@ static int _div_round_closest(const struct clk_div_table *table, down = _round_down_table(table, div); } - return (up - div) <= (div - down) ? up : down; + up_rate = DIV_ROUND_UP(parent_rate, up); + down_rate = DIV_ROUND_UP(parent_rate, down); + + return (rate - up_rate) <= (down_rate - rate) ? up : down; } static int _div_round(const struct clk_div_table *table, -- cgit v1.2.3 From 9315514252a95bca37be3ef8a93f835ed91c2855 Mon Sep 17 00:00:00 2001 From: Uwe Kleine-König Date: Sat, 21 Feb 2015 11:40:25 +0100 Subject: clk: divider: fix calculation of initial best divider when rounding to closest MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Similar to the reasoning for the previous commit DIV_ROUND_CLOSEST(parent_rate, rate) might not be the best integer divisor to get a good approximation for rate from parent_rate (given the metric for CLK_DIVIDER_ROUND_CLOSEST). For example assume a parent rate of 1000 Hz and a target rate of 700. Using DIV_ROUND_CLOSEST the suggested divisor gets calculated to 1 resulting in a target rate of 1000 with a delta of 300 to the desired rate. With choosing 2 as divisor however the resulting rate is 500 which is nearer to 700. Signed-off-by: Uwe Kleine-König Acked-by: Sascha Hauer Acked-by: Maxime Coquelin Signed-off-by: Michael Turquette --- drivers/clk/clk-divider.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'drivers/clk/clk-divider.c') diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c index 78b2e656ff6a..25006a8bb8e6 100644 --- a/drivers/clk/clk-divider.c +++ b/drivers/clk/clk-divider.c @@ -219,17 +219,18 @@ static int _div_round_closest(const struct clk_div_table *table, unsigned long parent_rate, unsigned long rate, unsigned long flags) { - int up, down, div; + int up, down; unsigned long up_rate, down_rate; - up = down = div = DIV_ROUND_CLOSEST(parent_rate, rate); + up = DIV_ROUND_UP(parent_rate, rate); + down = parent_rate / rate; if (flags & CLK_DIVIDER_POWER_OF_TWO) { - up = __roundup_pow_of_two(div); - down = __rounddown_pow_of_two(div); + up = __roundup_pow_of_two(up); + down = __rounddown_pow_of_two(down); } else if (table) { - up = _round_up_table(table, div); - down = _round_down_table(table, div); + up = _round_up_table(table, up); + down = _round_down_table(table, down); } up_rate = DIV_ROUND_UP(parent_rate, up); -- cgit v1.2.3