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Re: [PATCH review for 4.4 12/47] clk: wm831x: fix usleep_range with bad range

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On Fri, Sep 22, 2017 at 09:46:28AM +0100, Charles Keepax wrote:
>On Wed, Sep 20, 2017 at 04:45:02AM +0000, Levin, Alexander (Sasha Levin) wrote:
>> From: Nicholas Mc Guire <hofrat@osadl.org>
>>
>> [ Upstream commit ed784c532a3d0959db488f40a96c5127f63d42dc ]
>>
>> The delay here is not in atomic context and does not seem critical with
>> respect to precision, but usleep_range(min,max) with min==max results in
>> giving the timer subsystem no room to optimize uncritical delays. Fix
>> this by setting the range to 2000,3000 us.
>>
>> Fixes: commit f05259a6ffa4 ("clk: wm831x: Add initial WM831x clock driver")
>> Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
>> Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
>> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
>> Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
>> ---
>>  drivers/clk/clk-wm831x.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/clk/clk-wm831x.c b/drivers/clk/clk-wm831x.c
>> index 763aed2de893..dfedcf5bc429 100644
>> --- a/drivers/clk/clk-wm831x.c
>> +++ b/drivers/clk/clk-wm831x.c
>> @@ -101,7 +101,8 @@ static int wm831x_fll_prepare(struct clk_hw *hw)
>>  	if (ret != 0)
>>  		dev_crit(wm831x->dev, "Failed to enable FLL: %d\n", ret);
>>
>> -	usleep_range(2000, 2000);
>> +	/* wait 2-3 ms for new frequency taking effect */
>> +	usleep_range(2000, 3000);
>
>Does this patch really make sense for stable, isn't this really
>just a small optimisation? The patch is pretty harmless so I
>can't see applying it causing any problems, just curious what
>problems not having it is causing.

Looking back at this, I think I misunderstood a scenario in the scheduler this might be causing. What you say makes sense, I'll drop it.

-- 

Thanks,
Sasha

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[PATCH review for 4.4 01/47] drm_fourcc: Fix DRM_FORMAT_MOD_LINEAR  #define "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 19/47] IB/ipoib: rtnl_unlock can not come after  free_netdev "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 35/47] mmc: sdio: fix alignment issue in struct  sdio_func "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 37/47] netfilter: invoke synchronize_rcu after  set the _hook_ to NULL "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 11/47] sh_eth: use correct name for ECMR_MPDE  bit "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 21/47] drm/amdkfd: fix improper return value on  error "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 25/47] partitions/efi: Fix integer overflow in  GPT size calculation "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 15/47] iio: adc: hx711: Add DT binding for  avia,hx711 "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 22/47] USB: serial: mos7720: fix  control-message error handling "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 14/47] iio: adc: axp288: Drop bogus  AXP288_ADC_TS_PIN_CTRL register modifications "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 08/47] MIPS: ralink: Fix incorrect assignment  on ralink_soc "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 04/47] RDS: RDMA: Fix the composite message  user notification "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 12/47] clk: wm831x: fix usleep_range with bad  range "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
    Re: [PATCH review for 4.4 12/47] clk: wm831x: fix usleep_range with  bad range Charles Keepax <ckeepax@opensource.cirrus.com> - 2017-09-22 10:50 +0200
      Re: [PATCH review for 4.4 12/47] clk: wm831x: fix usleep_range with  bad range "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-24 02:20 +0200
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  [PATCH review for 4.4 40/47] netfilter: nfnl_cthelper: fix incorrect  helper->expect_class_max "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 05/47] ARM: dts: r8a7790: Use R-Car Gen 2  fallback binding for msiof nodes "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200
  [PATCH review for 4.4 18/47] IB/ipoib: Fix deadlock over vlan_mutex "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> - 2017-09-20 07:10 +0200

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