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

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Message-Id: <1554606804-29453-1-git-send-email-hofrat@opentech.at>
Date:   Sun,  7 Apr 2019 05:13:24 +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 RFC] 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.

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

Problem located with an experimental coccinelle script                                       
                                                                                             
Q: Basically usleep_range() with min == max never makes much sense notably                      
   in non-atomic context. If the factor of 2 is tolerable or a fixed
   offset of e.g. 1000 would be more suitable is not clear to me - maybe
   someone familiar with that driver can clarify this.
                                                                                             
Patch was compile tested with: u8500_defconfig (implies COMMON_CLK=y)
(with some sparse warnings about not implemented system calls)                               
                                                                                             
Patch is against 5.1-rc3 (localversion-next is next=20190405)                                

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

diff --git a/drivers/clk/ux500/clk-sysctrl.c b/drivers/clk/ux500/clk-sysctrl.c
index 7c0403b..a1fa3fb 100644
--- a/drivers/clk/ux500/clk-sysctrl.c
+++ b/drivers/clk/ux500/clk-sysctrl.c
@@ -42,7 +42,7 @@ 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*2);
 
 	return ret;
 }
-- 
2.1.4