@@ -129,12 +129,6 @@ static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
return DIV_ROUND_UP(parent_rate, div);
}
-/*
- * 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)
{
@@ -300,7 +294,7 @@ 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(divider, rate, now, best)) {
bestdiv = i;
This is a note to let you know that I have just added a patch titled clk: divider: fix calculation of maximal parent rate for a given divider to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt9. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From f5ea5f847b02319f6b3153c140fac3e74f10eb86 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@pengutronix.de> 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 commit da321133b53caf7889ed3ca1dabe4cc368db2604 upstream. 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 <s.hauer@pengutronix.de> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Michael Turquette <mturquette@linaro.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/clk/clk-divider.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)