linux-kernel - [PATCH V2] clk: ux500: add range to usleep

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Date:   Thu, 11 Apr 2019 13:04:11 +0200
From:   Nicholas Mc Guire <hofrat@...ntech.at>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nicholas Mc Guire <hofrat@...ntech.at>
Subject: [PATCH V2] clk: ux500: add range to usleep_range

Providing a range for usleep_range() allows the hrtimer subsystem to
coalesce timers - the delay is runtime configurable so a factor 2
is taken to provide the range. With the expected range for
enable_delay_us being milliseconds, the range should lie in the 250us
range which is sufficient for hrtimer optimization.

Signed-off-by: Nicholas Mc Guire <hofrat@...ntech.at>
---

Problem located with an experimental coccinelle script                                    
V2: As clarified by Ulf Hansson <ulf.hansson@...aro.org> the delays
    here are typically in the millisecond range - so as proposed
    replace the factor 2 by a 25% increase of max.

Patch was compile tested with: u8500_defconfig (implies COMMON_CLK=y)
(with some unrelated sparse warnings about not implemented system calls)                            
Patch is against 5.1-rc4 (localversion-next is next=20190410)

 drivers/clk/ux500/clk-sysctrl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/ux500/clk-sysctrl.c b/drivers/clk/ux500/clk-sysctrl.c
index 7c0403b..698306f 100644
--- a/drivers/clk/ux500/clk-sysctrl.c
+++ b/drivers/clk/ux500/clk-sysctrl.c
@@ -42,7 +42,8 @@ static int clk_sysctrl_prepare(struct clk_hw *hw)
 				clk->reg_bits[0]);
 
 	if (!ret && clk->enable_delay_us)
-		usleep_range(clk->enable_delay_us, clk->enable_delay_us);
+		usleep_range(clk->enable_delay_us, clk->enable_delay_us +
+			     (clk->enable_delay_us >> 2));
 
 	return ret;
 }
-- 
2.1.4