From: Guenter Roeck <linux@roeck-us.net>
To: Nicolin Chen <nicoleotsuka@gmail.com>
Cc: jdelvare@suse.com, linux-hwmon@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/5] hwmon: (ina3221) Make sure data is ready after channel enabling
Date: Wed, 17 Oct 2018 14:17:14 -0700 [thread overview]
Message-ID: <20181017211714.GB10990@roeck-us.net> (raw)
In-Reply-To: <20181017205348.GC15941@Asurada-Nvidia.nvidia.com>
On Wed, Oct 17, 2018 at 01:53:48PM -0700, Nicolin Chen wrote:
> Hello Guenter,
>
> On Wed, Oct 17, 2018 at 09:55:43AM -0700, Guenter Roeck wrote:
> > > @@ -676,6 +701,13 @@ static int __maybe_unused ina3221_resume(struct device *dev)
> > > if (ret)
> > > return ret;
> > >
> > > + /* Make sure data conversion is finished */
> > > + ret = ina3221_wait_for_data_if_active(ina);
> >
> > This is quite expensive and would delay resume (and enable, for that matter).
> > A less expensive solution would be to save the enable time here and in
> > ina3221_write_enable(). ina3221_wait_for_data_if_active() can then be called
> > from read functions and would wait if not enough time has expired.
> >
> > if (time_before(...))
> > usleep_range(missing wait time, missing_wait_time * 2);
> >
> > or something like that. This could be done per channel or, to keep
> > things simple, just using a single time for all channels.
>
> I was thinking something that'd fit one-shot mode too so decided
> to add a polling. But you are right. It does make sense to skip
> polling until an actual read happens, though it also feels a bit
> reasonable to me that putting a polling to the enabling routine.
>
> The wait time would be sightly more complicated than the polling
> actually, as it needs to involve total conversion time which may
> vary depending on the number of enabled channels. I will see what
> would be safer and easier and apply that in v2.
>
It isn't that complex; we have done it in other drivers. It is less
costly and has less overhead than extra i2c read operation(s).
Thanks,
Guenter
next prev parent reply other threads:[~2018-10-17 21:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-17 1:24 [PATCH 0/5] hwmon: (ina3221) Implement PM runtime to save power Nicolin Chen
2018-10-17 1:24 ` [PATCH 1/5] hwmon: (core) Inherit power properties to hdev Nicolin Chen
2018-10-17 19:44 ` Guenter Roeck
2018-10-17 20:15 ` Nicolin Chen
2018-10-18 11:37 ` Dan Carpenter
2018-10-17 1:24 ` [PATCH 2/5] hwmon: (ina3221) Return -ENODATA for two alarms attributes Nicolin Chen
2018-10-17 19:46 ` Guenter Roeck
2018-10-17 20:39 ` Nicolin Chen
2018-10-17 21:14 ` Guenter Roeck
2018-10-18 1:03 ` Nicolin Chen
2018-10-17 1:24 ` [PATCH 3/5] hwmon: (ina3221) Serialize sysfs ABI accesses Nicolin Chen
2018-10-17 1:24 ` [PATCH 4/5] hwmon: (ina3221) Make sure data is ready after channel enabling Nicolin Chen
2018-10-17 16:55 ` Guenter Roeck
2018-10-17 20:53 ` Nicolin Chen
2018-10-17 21:17 ` Guenter Roeck [this message]
2018-10-18 1:04 ` Nicolin Chen
2018-10-17 1:24 ` [PATCH 5/5] hwmon: (ina3221) Add PM runtime support Nicolin Chen
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