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Message-ID: <3eea7954-3faf-3fc9-7507-c318488c5524@gmail.com>
Date: Wed, 28 Sep 2022 14:14:14 +0300
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Jonathan Cameron <jic23@...nel.org>,
Matti Vaittinen <mazziesaccount@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Nikita Yushchenko <nikita.yoush@...entembedded.com>,
Cosmin Tanislav <demonsingur@...il.com>,
Jagath Jog J <jagathjog1996@...il.com>,
linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org,
"Mutanen, Mikko" <Mikko.Mutanen@...rohmeurope.com>,
"Haikola, Heikki" <Heikki.Haikola@...rohmeurope.com>
Subject: Re: [RFC PATCH 4/5] iio: accel: Support Kionix/ROHM KX022A
accelerometer
Hi Jonathan,
On 9/22/22 20:03, Jonathan Cameron wrote:
> On Wed, 21 Sep 2022 14:45:35 +0300
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
>> +
>> +/*
>> + * The sensor HW can support ODR up to 1600 Hz - which is beyond what most of
>> + * Linux CPUs can handle w/o dropping samples. Also, the low power mode is not
>> + * available for higher sample rates. Thus the driver only supports 200 Hz and
>> + * slower ODRs. Slowest being 0.78 Hz
>> + */
>> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("0.78 1.563 3.125 6.25 12.5 25 50 100 200");
>> +static IIO_CONST_ATTR(scale_available,
>> + "598.550415 1197.10083 2394.20166 4788.40332");
>> +
>> +static struct attribute *kx022a_attributes[] = {
>> + &iio_const_attr_sampling_frequency_available.dev_attr.attr,
>> + &iio_const_attr_scale_available.dev_attr.attr,
>
> Use the read_avail() callback instead of doing these as attributes.
> That makes the values available to consumer drivers...
Am I correct that populating the read_avail() does not add sysfs entries
for available scale/frequency? Eg, if I wish to expose the supported
values via sysfs I still need these attributes? Implementing the
read_avail() as well is not a problem though.
>> +static int kx022a_turn_on_unlock(struct kx022a_data *data)
>> +{
>> + int ret;
>> +
> This is not used enough that I can see a strong reason for the
> wrapper. Just put the two calls inline and rename the unlocked case.
In my opinion the kx022a_turn_on_unlock() and kx022a_turn_off_lock() do
simplify functions. Especially after I started using the
iio_device_claim_direct_mode() :) Thus I will leave these for the v2 -
please ping me again if you still want to see them removed (but I think
the usage of iio_device_claim_direct_mode() changed this to favour the
kx022a_turn_on_unlock() and kx022a_turn_off_lock()).
>> +static int kx022a_chip_init(struct kx022a_data *data)
>> +{
>> + int ret, dummy;
>> +
>> + /*
>> + * Disable IRQs because if the IRQs are left on (for example by
>> + * a shutdown which did not deactivate the accelerometer) we do
>> + * most probably end up flooding the system with unhandled IRQs
>> + * and get the line disabled from SOC side.
>> + */
>> + ret = regmap_write(data->regmap, KX022A_REG_INC4, 0);
>
> Unusual to do this rather than a reset. Quick look suggests there is
> a suitable software reset (CNTL2)
I switched to the software reset as you suggested. I am not really
convinced it is a better way. It seems the software reset requires us to
re-init the regmap cache. Well, I don't think it is a bid geal though -
just something worth noticing I guess.
>> +
>> +int kx022a_probe_internal(struct device *dev, int irq)
>> +{
>> + static const char * const regulator_names[] = {"io_vdd", "vdd"};
>> + struct iio_trigger *indio_trig;
>> + struct kx022a_data *data;
>> + struct regmap *regmap;
>> + unsigned int chip_id;
>> + struct iio_dev *idev;
>> + int ret;
>> +
>> + if (WARN_ON(!dev))
>> + return -ENODEV;
>> +
>> + regmap = dev_get_regmap(dev, NULL);
>> + if (!regmap) {
>> + dev_err(dev, "no regmap\n");
>
> Use dev_err_probe() for all dev_err() stuff in probe paths.
> It ends up cleaner and we don't care about the tiny overhead
> of checking for deferred.
This one bothers me a bit. It just does not feel correct to pass -EINVAL
for the dev_err_probe() so the dev_err_probe() can check if -EINVAL !=
-EPROBE_DEFER. I do understand perfectly well the consistent use of
dev_err_probe() for all cases where we get an error-code from a function
and return it - but using dev_err_probe() when we hard-code the return
value in code calling the dev_err_probe() does not feel like "the right
thing to do" (tm).
Eg, I agree that
return dev_err_probe(dev, ret, "bar");
is nice even if we know the function that gave us the "ret" never
requests defer (as that can change some day).
However, I don't like issuing:
return dev_err_probe(dev, -EINVAL, "bar");
Well, please let me know if you think the dev_err_probe() should be used
even in cases where we hard code the return to something...
For v2 I do change the other prints (like the one about failed regmap
read below).
>
>> +
>> + return -EINVAL;
>> + }
>> +
>> + idev = devm_iio_device_alloc(dev, sizeof(*data));
>> + if (!idev)
>> + return -ENOMEM;
>> +
>> + data = iio_priv(idev);
>> +
>> + /*
>> + * VDD is the analog and digital domain voltage supply
>> + * IO_VDD is the digital I/O voltage supply
>> + */
>> + ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(regulator_names),
>> + regulator_names);
>> + if (ret && ret != -ENODEV)
>> + return dev_err_probe(dev, ret, "failed to enable regulator\n");
>> +
>> + ret = regmap_read(regmap, KX022A_REG_WHO, &chip_id);
>> + if (ret) {
>> + dev_err(dev, "Failed to access sensor\n");
Yours,
-- Matti Vaittinen
--
--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~
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