Date:   Wed, 9 Jun 2021 03:38:56 +0000
From:   cy_huang(黃啟原) <cy_huang@...htek.com>
To:     "axel.lin@...ics.com" <axel.lin@...ics.com>
CC:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "u0084500@...il.com" <u0084500@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>
Subject: Re: [PATCH] regulator: rt6160: Convert to use
 regulator_set_ramp_delay_regmap

於 三，2021-06-09 於 11:32 +0800，Axel Lin 提到：
> cy_huang(黃啟原) <cy_huang@...htek.com> 於 2021年6月4日 週五 下午2:29寫道：
> >
> >
> >
> > 於 五，2021-06-04 於 13:59 +0800，Axel Lin 提到：
> >
> > cy_huang(黃啟原) <cy_huang@...htek.com> 於 2021年6月4日 週五 下午1:48寫道：
> >
> >
> >
> >
> > 於 五，2021-06-04 於 11:30 +0800，Axel Lin 提到：
> >
> > cy_huang(黃啟原) <cy_huang@...htek.com> 於 2021年6月4日 週五 上午10:26寫道：
> >
> >
> >
> >
> > cy_huang(黃啟原) <cy_huang@...htek.com> 於 2021年6月3日 週四 下午11:18寫道：
> >
> >
> > Hi,> >
> >
> >
> > cy_huang(黃啟原) <cy_huang@...htek.com> 於 2021年6月3日 週四 下午6:20寫道：
> >
> >
> >
> >
> > Hi, Axel:> Use regulator_set_ramp_delay_regmap instead of open-coded.
> >
> >
> >
> >
> >
> > There's some reason.
> > You can refer to https://lkml.org/lkml/2021/6/1/1145.
> >
> > It's because our ramp value order is from small to large, not large to
> > small.
> > It conflicts with find_closest_bigger value chosen logic.
> >
> > I have verified the rt6160_set_ramp_delay() behavior exactly the same as
> > regulator_set_ramp_delay_regmap. (both functions get the same selector
> > for a given delay)
> >
> > Could you check if this patch works?
> >
> > Sure.
> >
> > After my test sample code, below's the result.
> > ascending [1000 2500 5000 10000]
> > target =  1000 =>sel = 0
> > target =  2500 =>sel = 1
> > target =  5000 =>sel = 2
> > target = 10000 =>sel = 3
> > target =  1700 =>sel = 1
> > target =  2750 =>sel = 2
> > target =  7500 =>sel = 3
> > target = 15000 =>failed to find best select, sel = 3
> > target =     0 =>sel = 0
> > descending [10000 5000 2500 1000]
> > target =  1000 =>sel = 3
> > target =  2500 =>sel = 2
> > target =  5000 =>sel = 1
> > target = 10000 =>sel = 0
> > target =  1700 =>sel = 2
> > target =  2750 =>sel = 1
> > target =  7500 =>sel = 0
> > target = 15000 =>failed to find best select, sel = 0
> > target =     0 =>sel = 3
> >
> >
> > It means when target is in range or even over, the result are all correct.
> > But like as the ramp target is equal to 0, the selection will only choose the minimum one.
> > When the ramp target is equal to 0, it means the user want to disable the rammpping function.
> >
> > As I know, if target is equal to 0, it must find the fastest rampping value as the best selection.
> >
> >
> > If your table is [1000 2500 5000 10000], find_closest_bigger() will
> > choose sel=0 when ramp_delay=0.
> > If your table is [10000 5000 2500 1000], find_closest_bigger() will
> > choose sel=3 when ramp_delay=0.
> > i.e. In both cases, find_closest_bigger() chooses the fastest ramping value.
> >
> > This meets your exception.
> >
> > Actually, even if your table is [10000, 1000, 5000, 2500],
> > find_closest_bigger() still can choose the correct selector.
> > i.e. sel=1 when ramp_delay=0 in this case.
> >
> > This selection may be wrong.
> > ramp_delay=0 means ramp disabled,
> > If chip not support rampping disable, this selection must be configured as fastest rampping value, not the minimum
> > one.
> >
> >
> > 0 does not mean ramp disable.
> > It could be explicitly set to zero or its unintialized (zero by default).
> > see
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/regulator/core.c?id=1653ccf4c52df6
> > a4abe8ec2f33f2cb2896d129ea
> >
> > How about 'ramp_disable' falg is true?
> >
> >
> > My understanding is:
> > If the h/w does not support disabling ramp_delay, the regulator core
> > won't call ops->set_ramp_delay when ramp_delay=0.
> > If the h/w supports disabling ramp, i.e. ramp_disable flag is true,
> > the regulator core will
> > call ops->set_ramp_delay with ramp_delay=0. in this case, it should
> > have an exactly match and
> > write the register to disable ramp_delay.
> >
> >
> > If this can be guaranteed , to use the set_ramp_delay_regmap helper function would be better.
> Hi ChiYuan,
> Can you add  Reviewed-by or Acked-by if this patch works.
Sure, already tested.

Reviewed-by: ChiYuan Huang <cy_huang@...htek.com>
>
> Regards,
> Axel
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