Messages in this thread | | | Date | Thu, 28 Apr 2016 08:04:33 -0700 | From | Eduardo Valentin <> | Subject | Re: [PATCH 4/9] thermal: rockchip: handle the power sequence for tsadc controller |
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On Thu, Apr 28, 2016 at 09:50:29AM +0800, Caesar Wang wrote: > > > 在 2016年04月28日 07:48, Eduardo Valentin 写道: > >On Mon, Apr 18, 2016 at 11:35:56AM +0800, Caesar Wang wrote: > >>+ regmap_write(grf, GRF_TSADC_TESTBIT_L, GRF_TSADC_TSEN_PD_ON); > >>+ mdelay(10); > >>+ regmap_write(grf, GRF_TSADC_TESTBIT_L, GRF_TSADC_TSEN_PD_OFF); > >>+ udelay(100); /* The spec note says at least 15 us */ > >>+ regmap_write(grf, GRF_SARADC_TESTBIT, GRF_SARADC_TESTBIT_ON); > >>+ regmap_write(grf, GRF_TSADC_TESTBIT_H, GRF_TSADC_TESTBIT_H_ON); > >>+ udelay(200); /* The spec note says at least 90 us */ > >Does it make sense to use usleep_range() instead? > > I think so in the past, but I'm digging into the the udelay/usleep for > kernel.
What do you mean by in the past? timekeeping doc still recommends the range 10us to 20ms for usleep_range()
> > In general, > > udelay < 10us ~100us > mdelay > 1m, <1000ms/HZ > usleep_range(min,max) > 100us, <20ms
even here, your udelays could be replaced by usleep_range().
Any particular reason you believe spining is better than sleeping in your case?
> msleep > 20ms, < 1000ms > > So the udelay is suit for tsadc power sequence. > --- > > > Also, we have used the mdelay(10), so it doesn't matter if use the udelay. > After all the udelay is stable than the usleep_range.
What do you mean udelay is stable than usleep_range? usleep_range will give the opportunity to the scheduler to coalesce wakeups. udelay is a busyloop spin. Besides, I am not sure the current situation, but busylooping may be affected by cpu frequency.
> > -Caesar > > >1.9.1 > > > > > > > > > >-- > >Thanks, > >Caesar
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