Errors are communicated between the i2c controller layer and upper layers
(iicbus and slave device drivers) using a set of IIC_Exxxxxx constants which
effectively define a private number space separate from (and having values
that conflict with) the system errno number space. Sometimes it is necessary
to report a plain old system error (especially EINTR) from the controller or
bus layer and have that value make it back across the syscall interface
intact.
I initially considered replicating a few "crucial" errno values with similar
names and new numbers, e.g., IIC_EINTR, IIC_ERESTART, etc. It seemed like
that had the potential to grow over time until many of the errno names were
duplicated into the IIC_Exxxxx space.
So instead, this defines a mechanism to "encode" an errno into the IIC_Exxxx
space by setting the high bit and putting the errno into the lower-order
bits; a new errno2iic() function does this. The existing iic2errno()
recognizes the encoded values and extracts the original errno out of the
encoded value. An interesting wrinkle occurs with the pseudo-error values
such as ERESTART -- they aleady have the high bit set, and turning it off
would be the wrong thing to do. Instead, iic2errno() recognizes that lots of
high bits are on (i.e., it's a negative number near to zero) and just
returns that value as-is.
Thus, existing drivers continue to work without needing any changes, and
there is now a way to return errno values from the lower layers. The first
use of that is in iicbus_poll() which does mtx_sleep() with the PCATCH flag,
and needs to return the errno from that up the call chain.
Differential Revision: https://reviews.freebsd.org/D20975
The iicdev_writeto() function basically does scatter-gather IO by filling
in a pair of iic_msg structs to write the register address then the data
from different locations but with a single bus START/xfer/STOP sequence.
It turns out several low-level i2c controller drivers do not honor the
IIC_NOSTART flag, so the second piece of the write gets a new START on
the bus, and that confuses the ads111x chips which expect a continuous
write of 3 bytes to set a register.
A proper fix for this is to track down all the misbehaving controllers
drivers and fix them. For now this change makes this driver work again.
Also, disable the comparator by default; it's not used for anything.
The previous logic would start a measurement, and then pause_sbt() for the
averaging time currently configured in the chip. After waiting that long,
the code would blindly read the measurement register and return its value.
The problem is that the chip's idea of averaging time is based on its
internal free-running 1MHz oscillator, which may be running at a wildly
different rate than the kernel clock. If the chip's internal timer was
running slower than the kernel clock, we'd end up grabbing a stale result
from an old measurement.
The driver now still uses pause_sbt() to yield the cpu while waiting for
the measurement to complete, but after sleeping it checks the chip's status
register to ensure the measurement engine is idle. If it's not, the driver
uses a retry loop to wait a bit (5% of the original wait time) then check
again for completion.
Instances of the device can be configured using hints or FDT data.
Interfaces to reconfigure the chip and extract voltage measurements from
it are available via sysctl(8).
features offered by the chips.
For 2127 and 2129 chips, fix the detection of when chip-init is needed. The
chip config needs to be reset whenever power was lost, but the logic was
wrong for 212x chips (it only worked for 8523). Now the "oscillator
stopped" bit rather than the power manager mode is used to detect startup
after powerfail.
For all chips, disable the clock output pin.
For chips that have a timestamp/tamper-monitor feature, turn off monitoring
of the timestamp trigger pin.
The 8523, 2127, and 2129 chips have a "power manager" feature that offers
several options. We've been using the default mode which enables
everything. Now the code sets the power manager options to
- direct-switch (when Vdd < Vbat, without extra threshold check)
- no battery monitor
- no external powerfail monitor
This reduces the current draw while running on battery from 1930nA to 880nA,
which should roughly double the lifespan of the battery under load.
Because battery checking is a nice thing to have, the code now does a check
at startup, and then once a day after that, instead of checking continuously
(but only actually reporting at startup). The battery check is now done by
setting the power manager back to default mode, sleeping briefly while it
makes a voltage measurement, then switching back to power-saving mode.
This affects the detection of 24-hour vs AM/PM mode... the ampm bit is in a
different location on 2127 and 2129 chips compared to other nxp rtc chips.
I noticed the 2127 case wasn't being handled correctly when I accidentally
misconfiged my system by claiming my PCF2129 was a 2127.
on PCx2129 chips too.
The datasheet for the PCx2129 chips says that there is only a watchdog
timer, no countdown timer. It turns out the countdown timer hardware is
there and works just the same as it does on a PCx2127 chip, except that you
can't use it to trigger an interrupt or toggle an output pin. We don't need
interrupts or output pins, we only need to read the timer register to get
sub-second resolution. So start treating the 2129 chips the same as 2127.
An obscure footnote in the datasheets for the PCx2127, PCx2129, and
PCF8523 rtc chips states that the chips do not support i2c repeat-start
operations. When the driver was originally written and tested, the i2c
bus on that system also didn't support repeat-start and just quietly
turned repeat-start operations into a stop-then-start, making it appear
that the nxprtc driver was working properly.
The repeat-start situation only comes up on reads, so instead of using
the standard iicdev_readfrom(), use a local nxprtc_readfrom(), which is
just a cut-and-pasted copy of iicdev_readfrom(), modified to send two
separate start-data-stop sequences instead of using repeat-start.
r348164 added code to iicbus_request_bus/iicbus_release_bus to automatically
call device_busy()/device_unbusy() as part of aquiring exclusive use of the
bus (so modules can't be unloaded while the bus is exclusively owned and/or
IO is in progress). That broke the ability to do i2c IO from a slave device
probe method, because the slave isn't attached yet, so calling device_busy()
triggers a sanity-check panic for trying to busy a non-attached device.
Now we check whether the device status is < DS_ATTACHING, and if so we busy
the iicbus rather than the slave device. I think this leaves a small window
where a module could be unloaded while probing is in progress. But I think
that's true of all devices, and probably should be fixed by introducing a
DS_PROBING state for devices, and handling that at various points in the
newbus code.
Since drm2 removal, there has not been any consumer of the feature in the
tree. I am also unaware of any out-of-tree consumer.
More importantly, the feature has been broken from the very start, both
before and after r306589, because the ivar was set on a device that does
not support it and it was read from another device that also does not
support it.
A bus-wide no-stop flag cannot be implemented as an ivar as iicbus
attaches as a child of various drivers. Implementing the ivar in each
and every I2C driver is just impractical.
If we ever want to implement this feature properly, then probably the
easiest way to do it would be via a flag in the softc of iicbus.
In fact, we might have to do that in the stable branches if we want to
fix the code for them.
Reported by: ian (long time ago)
MFC after: 1 month (maybe)
X-MFC-note: cannot just merge the change, must keep drm2 happy
Pnpinfo is bus-specific and requires the bus name. The FDTCOMPAT_PNP_INFO()
macro makes it easier to define new FDT-based pnpinfo for busses other than
simplebus.
Differential Revision: https://reviews.freebsd.org/D20382
Many i2c slave drivers are in modules that can be unloaded. If they detach
while IO is in progress the bus would be hung forever. Conversely,
lower-layer drivers (iicbus and the hardware driver) also live in modules
and other kinds of bad things happen if they get detached while IO is in
progress. Because device_busy() propagates up to parents, marking the slave
device busy while it owns the bus solves both kinds of problems that come
with detaching i2c devices while IO is in progress.
Instead of precalculating the different speed, respect the bus frequency
and calculate the clock register parameter based on it.
If the platform didn't register the core clk, fallback on the precomputed
values (This is likely do be the case on Marvell boards).
Add the ability to use interrupts for i2c message.
We still use polling for early boot i2c transfer (for PMIC
for example) but as soon as interrupts are available use them.
On Allwinner SoC >A20 is seems that polling mode is broken for some
reason, this is now fixed by using interrupt mode.
For Allwinner also fix the frequency calculation, the one in the code
was for when the APB frequency is at 48Mhz while it is at 24Mhz on most
(all?) Allwinner SoCs. We now support both cases.
While here add more debug info when it's compiled in.
Tested On: A20, H3, A64
MFC after: 1 month
OF_getprop_alloc takes element size argument and returns number of
elements in the property. There are valid use cases for such behavior
but mostly API consumers pass 1 as element size to get string
properties. What API users would expect from OF_getprop_alloc is to be
a combination of malloc + OF_getprop with the same semantic of return
value. This patch modifies API signature to match these expectations.
For the valid use cases with element size != 1 and to reduce
modification scope new OF_getprop_alloc_multi function has been
introduced that behaves the same way OF_getprop_alloc behaved prior to
this patch.
Reviewed by: ian, manu
Differential Revision: https://reviews.freebsd.org/D14850
of years since the century, so strip the century out when converting to or
from bcd_clocktime format (the conversion routines will infer century by
pivoting on 70).
rather than relying on a set of canned EARLY_DRIVER_MODULE() statements in
the ofw_iicbus source. This means hw drivers will no longer be required to
use one of a few predefined driver names. They will also now be able to
decide themselves if they want to use DRIVER_MODULE or EARLY_DRIVER_MODULE
and to set which pass to attach on for early modules.
Mainly, this adds extern declarations for the driver and devclass variables.
It also renames ofwiicbus_devclass to ofw_iicbus_devclass to be consistant
with the way we use ofw_ prefixes on this stuff.
The driver now ensures only one thread at a time is running in the API
functions (clock_gettime() and clock_settime()) by specifically requesting
ownership of the i2c bus without using IIC_RECURSIVE, then it does all IO
using IIC_RECURSIVE so that each individual IO operation doesn't try to
re-acquire the bus.
The other IO done by the driver happens at attach or intr_config_hooks time,
when there can't be multiple threads running with the same device instance.
So, the IIC_RECURSIVE flag can be safely ORed into the wait flags for all IO
done by the driver, because it's all either done in a single-threaded
environment, or protected within a block bounded by explict
iicbus_acquire_bus() and iicbus_release_bus() calls.
The driver now ensures only one thread at a time is running in the API
functions (clock_gettime() and clock_settime()) by specifically requesting
ownership of the i2c bus without using IIC_RECURSIVE, then it does all IO
using IIC_RECURSIVE so that each individual IO operation doesn't try to
re-acquire the bus.
The other IO done by the driver happens at attach or intr_config_hooks time,
when there can't be multiple threads running with the same device instance.
So, the IIC_RECURSIVE flag can be safely ORed into the wait flags for all IO
done by the driver, because it's all either done in a single-threaded
environment, or protected within a block bounded by explict
iicbus_acquire_bus() and iicbus_release_bus() calls.
The recursive ownership support added in r321584 was unconditionally in
effect all the time -- whenever a given i2c slave device instance tried to
lock the i2c bus for exclusive use when it already owned the bus, the call
returned immediately without waiting. However, many i2c slave drivers use
bus ownership to enforce that only a single thread at a time can be using
the slave device. The recursive locking changes broke this use case.
Now there is a new flag, IIC_RECURSIVE, which can be mixed in with the
other flags passed to iicbus_acquire_bus() to allow drivers to indicate
when recursive locking is desired. Using the flag implies that the driver
is managing concurrent access to the device by different threads in some way.
This immediately fixes all existing i2c slave drivers except for the two
i2c RTC drivers which use the recursive locking feature; those will be
fixed in a followup commit.
