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List: openbsd-arm
Subject: Re: sxitwi on orangepi one (H3) re-visited
From: "Stephen Graf" <s_graf () telus ! net>
Date: 2018-01-07 21:35:14
Message-ID: 000001d387ff$68466350$38d329f0$ () telus ! net
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Please disregard this update. There is a typo and I could not have tested
it, probably did not notice that the build failed. I will try again on ver
1.7.
-----Original Message-----
From: Stephen Graf [mailto:s_graf@telus.net]
Sent: Friday, January 5, 2018 9:35 PM
To: 'Mark Kettenis' <mark.kettenis@xs4all.nl>
Cc: arm@openbsd.org; artturi.alm@gmail.com
Subject: RE: sxitwi on orangepi one (H3) re-visited
Thank you for the work you are doing on this driver.
Attached is a diff to ver 1.6 that implements the bus reset on error. I
tested this on my orange pi one.
-----Original Message-----
From: owner-arm@openbsd.org [mailto:owner-arm@openbsd.org] On Behalf Of Mark
Kettenis
Sent: Friday, January 5, 2018 5:23 AM
To: s_graf@telus.net
Cc: arm@openbsd.org; artturi.alm@gmail.com
Subject: Re: sxitwi on orangepi one (H3) re-visited
> From: "Stephen Graf" <s_graf@telus.net>
> Date: Thu, 4 Jan 2018 16:23:56 -0800
>
> I tested your simplification changes with success.
>
> Then I removed the wait code in send stop, retested and again had
success.
> You should be able to convince yourself that it is not necessary to
> wait for the stop code to complete, since there is no status code nor
> interrupt for stop complete. Also from the Allwinner docs, it is
> possible to assert the stop and start bits at the same time, again
> implying that the software does not have to wait for the stop. The
> i2c protocol supports multiple masters and so a potential master must
> monitor the bus and wait for a bus idle condition (which a stop
> generates), before attempting a start. The Allwinner hardware does
> the idle bus check and wait in the start bit processing. Since the
> only thing that is possible after a stop is a start, there seems to be
> no reason for the software to wait for the stop to complete and that
> is why there is no hardware to check for a stop to complete.
I re-tested the A20 yesterday and removing the polling loop after sending a
STOP works just fine there as well. So I adjusted my diff an committed it.
That should allow us to focus on the other issues.
We really try to seperate out issues and address them with individual
patches.
> Regarding the bus speed, I would like to recommend that bus speed
> information be put in the dtb. It could be as simple as specifying
> the M and N values. The driver could generate defaults if there is
> nothing specified in the dtb. I do not think there should be a lot of
> code in the driver to try to calculate a speed from the master clock.
> The dtb for the orange pi one comes with the i2c busses disabled and I
> have to edit it anyway to enable them and add the i2c devices.
The i2c bindings allow you to add a "clock-frequency" property to the i2c
controller node to specify the desired bus clock frequency. See
Documentation/devicetree/bindings/i2c/{i2c.txt|i2c-mv64xxx.txt} in the Linux
source tree for details. If the property is absent the standard speed of
100000 Hz is assumed. While none of the Allwinner device trees seem to
include this property, it is easy to look for it anyway.
> I then went on and added/modified the driver for interrupts and
> successfully tested. I tested with two bme280 sensors. The setup
> code on the bme280 driver is done at boot (attach) time and has to use
> polling, while the cyclic ongoing read of the sensors is done with
interrupts.
>
> Console boot extract:
> com0: console
> sxitwi0 at simplebus0
> iic0 at sxitwi0
> bme0 at iic0 addr 0x77: BME280 60
> sxitwi1 at simplebus0
> iic1 at sxitwi1
> bme1 at iic1 addr 0x76: BME280 60
> ampintc0 at simplebus0 nirq 160, ncpu 4
> sxirtc0 at simplebus0
>
> Sensor readout:
> openbsdop1$ sysctl hw.sensors
> hw.sensors.bme0.temp0!.89 degC
> hw.sensors.bme0.humidity05.23%
> hw.sensors.bme0.pressure00.79 Pa
> hw.sensors.bme1.temp0 .83 degC
> hw.sensors.bme1.humidity0@.87%
> hw.sensors.bme1.pressure00.83 Pa
> openbsdop1$
>
> Attached are files for a diff from ver 1.5, the same diff with notes
> and the entire driver code as tested. Would you please review the
> code and test if possible on any devices you have. If you have
> questions/suggestions please reply.
I think I know how to re-implement the interrupt support properly.
Currently testing this approach. I'll also handle the bus clock speed issue
as I know how to do that properly now. But if you could at some point send
me a new diff for adding the reset functionality, that would be great.
Please use diff -up to generate your diffs and avoid making arbitrary
whitespace changes. We use tabs instead of spaces when possible and not
following our standards results in noisy diffs that are harder to review.
Cheers,
Mark
> -----Original Message-----
> From: owner-arm@openbsd.org [mailto:owner-arm@openbsd.org] On Behalf
> Of Mark Kettenis
> Sent: Wednesday, January 3, 2018 1:03 PM
> To: s_graf@telus.net
> Cc: arm@openbsd.org; artturi.alm@gmail.com
> Subject: Re: sxitwi on orangepi one (H3) re-visited
>
> > From: "Stephen Graf" <s_graf@telus.net>
> > Date: Tue, 2 Jan 2018 11:16:18 -0800
> >
> > I did some further testing with interrupts and set the BME280 device
> > to use interrupts on setup. This occurs in the attach phase on
> > system boot. It did not work even after I added an early start to
> > the ampintc
> driver:
> >
> > sxipio0 at simplebus0: 94 pins
> > ampintc0 at simplebus0 nirq 160, ncpu 4
> > sxipio1 at simplebus0: 12 pins
> >
> > I suspect that interrupts are not set up on system boot so I went
> > back to the BME280 code that does device setup non-interrupt and
> > cyclic read with interrupt.
>
> Yes. On OpenBSD, interrupts remain disabled until late in the
> autoconf procedure. Up until that point, the global variable "cold"
> remains set to 1. This is why many drivers check this variable and
> poll for command completion as long as cold is non-zero.
>
> > I am not happy to rip out the interrupt code that I have tested and
> > works on the H3 device. I looked at the V40 docs and they seem to
> > be identical to the H3 for the TWI. If the code does not meet
> > openBSD standards I am quite willing to work to get it right. The
> > code I provided also works in non-interrupt mode.
>
> Yes the hardware blocks seem to be identical.
>
> > Could we work together on the interrupt code and get the whole
> > driver working properly? It should not be a major effort.
>
> Certainly. I'm just proposing to remove the bogus code such that we
> can see things a bit more clearly.
> >
> > As I mentioned above there is an issue trying to use interrupts on
> > system boot.
> >
> > -----Original Message-----
> > From: owner-arm@openbsd.org [mailto:owner-arm@openbsd.org] On Behalf
> > Of Stephen Graf
> > Sent: Sunday, December 31, 2017 11:57 AM
> > To: 'Mark Kettenis' <mark.kettenis@xs4all.nl>
> > Cc: arm@openbsd.org; artturi.alm@gmail.com
> > Subject: Re: sxitwi on orangepi one (H3) re-visited
> >
> > Thank you for looking at my code. I will try your code on my orange
> > pi one in the near future.
> >
> > Regarding the wait for bus free a on stop condition: After a stop,
> > the only thing that can be done is a start. When the start bit is
> > set the controller "will transmit a START condition on the bus when
> > the bus is free". So the wait is done by the hardware in the start
> > routine. It is necessary for the start hardware to wait for a free
> > bus as it could be a different independent master waiting to grab
> > the bus. Have you tested without any stop delay? It works, as it
should, on my system.
>
> I did test this on the A20 system, and it failed there. But my
> testing may have been flawed. I'll re-test.
>
> > Regarding the bus reset: When (not if!) an error occurs, it is
> > important to reset to a known default state. This incudes not only
> > the hardware but also flags such as the started flag. In my
> > testing, I had an issue with the power lead to the sensor on my
> > breadboard being intermittent. Without the reset the sensor would
> > often permanently quit on an error. With the reset it would work
> > again on the
> next read.
>
> Right. What state did you end up in when this happens?
>
> > My programming experience dates back to writing assembler code on
> > mini computers to control monstrous paper making machines. Things
> > would often go wrong and sending an error message to a remote
> > console was never an acceptable solution.
> >
> > Regarding the bus clock speed: Ideally this should be as parameter
> > set outside of the driver on system startup. Different applications
> > require different bus speeds and one bus should be able to run at a
> > different speed than another. It should not be necessary to
> > recompile the kernel to change the bus speed.
> >
> > Does the existing driver work with interrupts on any of your hardware?
>
> Yes. It works on the A20, but not on the V40.
>
> > -----Original Message-----
> > From: Mark Kettenis [mailto:mark.kettenis@xs4all.nl]
> > Sent: Sunday, December 31, 2017 4:06 AM
> > To: s_graf@telus.net
> > Cc: arm@openbsd.org; mark.kettenis@xs4all.nl; artturi.alm@gmail.com
> > Subject: Re: sxitwi on orangepi one (H3) re-visited
> >
> > > From: "Stephen Graf" <s_graf@telus.net>
> > > Date: Thu, 14 Dec 2017 12:54:02 -0800
> > >
> > > My recent experience with the dwxe driver has emboldened me to
> > > look at the sxitwi driver again. A few months ago I worked with
> > > Artturi Alm to get the driver working with a driver he wrote for a
> > > BME280
> sensor.
> > > At that time I tested the non-interrupt option (I2C_F_POLL) only.
> > > This time I tried the interrupt option as I thought it would be
> > > more appropriate in a production situation. The non-interrupt
> > > option can tie up the system for periods of time.
> > >
> > > My environment is an orange pi one (Allwinner H3) with one BME280
> > > sensor on i2c bus 0 and another on bus 1. Most of my testing was
> > > done with a scope on the SDA and SCL lines of bus 0 and printf
> > > statements in the drivers. The
> > > BME280 driver does a lot of device calibration reading and setup
> > > in the attach phase and then reads data once a second into sysctl
> hw.sensors.
> > >
> > > My first issue is that the dtb has the i2c busses disabled. So I
> > > had to dtc the dtb, enable the busses 0 and 1 and add BME280
> > > sections to the i2c busses. The dtb provides a third i2c bus, but
> > > the orange pi one does not bring it out to the header and so it
> > > makes no sense to enable
> > it.
> > >
> > > A serious issue that hindered my testing is that the printf
> > > statements in the driver affected the console driver, garbling the
> > > output and often stopping all output and input. The output always
> > > appeared correctly in the message log file. Even now it seems
> > > that the console is affected when the sxitwi driver is in use and
> > > there is a lot of other
> > console output.
> > >
> > > Another item I noticed is that the i2c busses were running at half
> > > the standard speed of 100kHz. The comments in the driver code,
> > > which are taken right out of the Allwinner doc, set the speed for
> > > a 48MHz master
> > clock.
> > > However, the orange pi one runs at 24MHz.
> > >
> > > The sxitwi driver was sprinkled with delays. I took most of them
> > > out without any side effects.
> > >
> > > I added a bus reset function to help in error recovery.
> > >
> > > In my testing I left the BME280 driver to do device initialization
> > > in non-interrupt mode and only changed the cyclic data read to use
> > interrupts.
> > > This made testing easier as it is hard to capture something on a
> > > scope that happens only on system boot. Also I am not clear if
> > > interrupts are working at system boot. It seems that the
> > > interrupt controller is set up after the sxitwi controller.
> > >
> > > It looks like the device status can change after the interrupt is
> > > released in the interrupt service routine, sxitwi_intr. Therefore
> > > I saved the status for later use when the driver wakes up in
> > > sxitwi_wait. To make that work I separated the interrupt and
> > > non-interrupt parts of sxitwi_wait and added some recovery code.
> > >
> > > I took out a lot of the sxitwi_send_stop code because as the
> > > comment says "Interrupt is not generated" and there is no need to
> > > do
anything.
> > > The next send start will wait, or for that matter another master
> > > on the bus may be trying to do a start and will wait for the stop
> > > to
> > complete.
> > >
> > > I sort of messed up the formatting (tabs spaces?) with all my
> > > changes and I hesitate do show a diff. The working code for
> > > sxitwi and BNE280 drivers is attached. Is the sxitwi driver used
> > > by any other devices other than Allwinner? Is anyone interested
> > > in testing my
> code?
> >
> > Hi Stephen,
> >
> > The sxitwi(4) driver indeed doesn't work very well on the newer SoCs.
> > But it works fine on my Allwinner A20 board.
> >
> > As I now have a Banana Pi M2 Berry with an AXPI221a PMIC connected
> > over I2C I made some time to look into the issue. There are some
> > things in your diff that didn't make a lot of sense, but while
> > trying to fix them in a better way, I only managed to make things
> > worse it seems. So I've taken the radical approach to disable
> > interrupt mode completely for now. Together with the removal of the
> > the excessive delays that seems to make things much better on both
> > the A20 and the
> > V40 boards that periodically read the PMIC registers to update
> > sensor values. My plan is to commit the diff below unless some
> > other developer objects to it and then see if I can properly fix
interrupt mode.
> >
> > Regarding you conclusions and questions above:
> >
> > Yes, I came to the conclusion that the bus is running at half the
> > speed as well. The proper solution is to calculate the dividers
> > based on the input frequency instead of hardcoding them. The input
> > frequency can be found by calling clock_get_frequency(). I might
> > need to add a few more clocks to
> > sxiccmu(4) first for this to work, so I'll address that in a future
diff.
> > Running the I2C bus at 50 kHz is probably fine for most I2C devices.
> >
> > We do need to make sure the bus is idle after sending a STOP before
> > starting another transfer. So your change twsi_send_stop() is not ok.
> >
> > I'm not sure under what circumstances a bus reset would help. Linux
> > doesn't seem to implement one. So I left that bit out for now.
> >
> > I think it would be ok to add the BME280 driver to the tree, but it
> > needs some cleanup first. Normal code should not use symbols that
> > start with an underscore! I also don't think we should document
> > registers in the source code when documentation is publically
available.
> >
> > Cheers,
> >
> > Mark
> >
> >
> > Index: dev/fdt/sxitwi.c
> > ==================================================================> > RCS file: \
> > /cvs/src/sys/dev/fdt/sxitwi.c,v retrieving revision 1.5
> > diff -u -p
> > -r1.5 sxitwi.c
> > --- dev/fdt/sxitwi.c 30 Dec 2017 19:04:00 -0000 1.5
> > +++ dev/fdt/sxitwi.c 31 Dec 2017 11:36:32 -0000
> > @@ -128,12 +128,6 @@
> >
> > #define SOFTRESET_VAL 0 /* reset value */
> >
> > -#define TWSI_RETRY_COUNT 1000 /* retry loop
count
> > */
> > -#define TWSI_RETRY_DELAY 1 /* retry delay */
> > -#define TWSI_STAT_DELAY 1 /* poll status
delay
> > */
> > -#define TWSI_READ_DELAY 2 /* read delay */
> > -#define TWSI_WRITE_DELAY 2 /* write delay */
> > -
> > struct sxitwi_softc {
> > struct device sc_dev;
> > bus_space_tag_t sc_iot;
> > @@ -291,21 +285,13 @@ sxitwi_bus_scan(struct device *self, str u_int
> > sxitwi_read_4(struct sxitwi_softc *sc, u_int reg) {
> > - u_int val = bus_space_read_4(sc->sc_iot, sc->sc_ioh, reg);
> > -
> > - delay(TWSI_READ_DELAY);
> > -
> > - return val;
> > + return bus_space_read_4(sc->sc_iot, sc->sc_ioh, reg);
> > }
> >
> > void
> > sxitwi_write_4(struct sxitwi_softc *sc, u_int reg, u_int val) {
> > bus_space_write_4(sc->sc_iot, sc->sc_ioh, reg, val);
> > -
> > - delay(TWSI_WRITE_DELAY);
> > -
> > - return;
> > }
> >
> > int
> > @@ -317,7 +303,6 @@ sxitwi_intr(void *arg)
> > val = sxitwi_read_4(sc, TWSI_CONTROL);
> > if (val & CONTROL_IFLG) {
> > sxitwi_write_4(sc, TWSI_CONTROL, val & ~CONTROL_INTEN);
> > - wakeup(&sc->sc_dev);
> > return 1;
> > }
> > return 0;
> > @@ -364,19 +349,19 @@ int
> > sxitwi_send_stop(void *v, int flags) {
> > struct sxitwi_softc *sc = v;
> > - int retry = TWSI_RETRY_COUNT;
> > + int timo;
> >
> > sc->sc_started = 0;
> >
> > /* Interrupt is not generated for STAT_NRS. */
> > sxitwi_write_4(sc, TWSI_CONTROL, CONTROL_STOP |
sc->sc_twsien_iflg);
> > - while (--retry > 0) {
> > + for (timo = 100; timo > 0; timo--) {
> > if (sxitwi_read_4(sc, TWSI_STATUS) == STAT_NRS)
> > return 0;
> > - delay(TWSI_STAT_DELAY);
> > + delay(1);
> > }
> >
> > - return -1;
> > + return ETIMEDOUT;
> > }
> >
> > int
> > @@ -458,30 +443,21 @@ int
> > sxitwi_wait(struct sxitwi_softc *sc, u_int control, u_int expect,
> > int
> > flags) {
> > u_int status;
> > - int timo, error = 0;
> > + int timo;
> >
> > - delay(5);
> > - if (!(flags & I2C_F_POLL))
> > - control |= CONTROL_INTEN;
> > sxitwi_write_4(sc, TWSI_CONTROL, control | sc->sc_twsien_iflg);
> >
> > - timo = 0;
> > - do {
> > + for (timo = 10000; timo > 0; timo--) {
> > control = sxitwi_read_4(sc, TWSI_CONTROL);
> > if (control & CONTROL_IFLG)
> > break;
> > - if (flags & I2C_F_POLL)
> > - delay(TWSI_RETRY_DELAY);
> > - else {
> > - error = tsleep(&sc->sc_dev, PWAIT, "sxitwi", 100);
> > - if (error)
> > - return error;
> > - }
> > - } while (++timo < 1000000);
> > + delay(1);
> > + }
> > + if (timo == 0)
> > + return ETIMEDOUT;
> >
> > status = sxitwi_read_4(sc, TWSI_STATUS);
> > if (status != expect)
> > return EIO;
> > -
> > - return error;
> > + return 0;
> > }
> >
> >
> >
> >
>
>
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