Re: [PATCH] misc/pca9552: Add qom set and get

[Philippe Mathieu-Daudé]

On 11/19/19 5:27 PM, Cédric Le Goater wrote:
> On 18/11/2019 18:48, Philippe Mathieu-Daudé wrote:
> > Odd... I only received Cédric answer, not Joel patch.
> >
> > On 11/18/19 11:00 AM, Cédric Le Goater wrote:
> > > On 18/11/2019 07:17, Joel Stanley wrote:
> > > > Following the pattern of the work recently done with the ASPEED GPIO
> > > > model, this adds support for inspecting and modifying the PCA9552 LEDs
> > > > from the monitor.
> > > >
> > > >    (qemu) qom-set  /machine/unattached/device[17] led0 on
> > > >    (qemu) qom-get  /machine/unattached/device[17] led0
> > > >    "on"
> > > >
> > > >    (qemu) qom-set  /machine/unattached/device[17] led0 off
> > > >    (qemu) qom-get  /machine/unattached/device[17] led0
> > > >    "off"
> > > >
> > > >    (qemu) qom-set  /machine/unattached/device[17] led0 pwm0
> > > >    (qemu) qom-get  /machine/unattached/device[17] led0
> > > >    "pwm0"
> > > >
> > > >    (qemu) qom-set  /machine/unattached/device[17] led0 pwm1
> > > >    (qemu) qom-get  /machine/unattached/device[17] led0
> > > >    "pwm1"
> > >
> > > It would be nice to revive the QOM get patchset from David.
> > >
> > >      http://patchwork.ozlabs.org/patch/666458/
> > >
> > > Did we reach some consensus ?
> > >
> > > > Signed-off-by: Joel Stanley <address@hidden>
> > >
> > > Some comments below.
> > >
> > > > ---
> > > > The qom device in mainline qemu is a different path. Using the monitor
> > > > examine `info qom-tree /machine/unattached/` to discover it.
> > > >
> > > > This can be tested with a Witherspoon image.
> > > >
> > > > $ wget 
> > > > https://openpower.xyz/job/openbmc-build/distro=ubuntu,label=builder,target=witherspoon/lastSuccessfulBuild/artifact/deploy/images/witherspoon/obmc-phosphor-image-witherspoon.ubi.mtd
> > > >
> > > > $ qemu-system-arm -M witherspoon-bmc -serial pty -monitor pty -nographic \
> > > >    -drive file=obmc-phosphor-image-witherspoon.ubi.mtd,format=raw,if=mtd
> > > > char device redirected to /dev/pts/5 (label compat_monitor0)
> > > > char device redirected to /dev/pts/10 (label serial0)
> > > >
> > > > $ screen /dev/pts/5
> > > > QEMU 4.1.91 monitor - type 'help' for more information
> > > > (qemu) qom-get  /machine/unattached/device[17] led0
> > > > "off"
> > > >
> > > > $ screen /dev/pts/19
> > > > root@witherspoon:~# cd /sys/class/gpio/
> > > > root@witherspoon:/sys/class/gpio# echo 248 > export
> > > > root@witherspoon:/sys/class/gpio# cat gpio248/value
> > > > 0
> > > >
> > > > (qemu) qom-set  /machine/unattached/device[17] led0 on
> > > >
> > > > root@witherspoon:/sys/class/gpio# echo out > gpio248/direction
> > > > root@witherspoon:/sys/class/gpio# cat gpio248/value
> > > > 1
> > > >
> > > > (qemu) qom-get  /machine/unattached/device[17] led0
> > > > "on"
> > > >
> > > > (qemu) qom-set  /machine/unattached/device[17] led0 off
> > > > (qemu) qom-get  /machine/unattached/device[17] led0
> > > > "off"
> > > >
> > > > root@witherspoon:/sys/class/gpio# cat gpio248/value
> > > > 0
> >
> > I am assuming this is 5.0 material.
> >
> > This is a good starting point, and is useful.
> >
> > However this would be useful for other boards/devices too.
> >
> > What about defining a InterfaceInfo[] for external GPIOs?
>
> The code below is very specific to pca9552.

Yes, sorry if I was unclear, I don't want to delay this series, I was 
just thinking about other uses.

> What kind of interface do you have in mind more precisely ?
> which handlers ?

Here we expose the devices GPIOs (as output) so they can be modified via 
QMP.

A QMP client could subscribe to GPIOs input events (or IRQ triggered).

(The PCA9552 can also use the 16 lines as input, but Joel added a "input 
line behaviour not modeled" comment below).

Maybe the PCA9552 isn't the best example for my generic use case, 
because it is already "out of the soc/board" being on a bus.

I'm more concerned about a generic QMP way to access GPIOs from a SoC 
exposed to a physical user of a board.

> > Shouldn't we use the qemu_irq type for that then?
> >
> > > > Signed-off-by: Joel Stanley <address@hidden>
> > > > ---
> > > >    hw/misc/pca9552.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
> > > >    1 file changed, 91 insertions(+)
> > > >
> > > > diff --git a/hw/misc/pca9552.c b/hw/misc/pca9552.c
> > > > index 73be28d9369c..0362aac8c862 100644
> > > > --- a/hw/misc/pca9552.c
> > > > +++ b/hw/misc/pca9552.c
> > > > @@ -15,12 +15,16 @@
> > > >    #include "hw/misc/pca9552.h"
> > > >    #include "hw/misc/pca9552_regs.h"
> > > >    #include "migration/vmstate.h"
> > > > +#include "qapi/error.h"
> > > > +#include "qapi/visitor.h"
> > > >      #define PCA9552_LED_ON   0x0
> > > >    #define PCA9552_LED_OFF  0x1
> > > >    #define PCA9552_LED_PWM0 0x2
> > > >    #define PCA9552_LED_PWM1 0x3
> > > >    +static const char *led_state[] = {"on", "off", "pwm0", "pwm1"};
> >
> > BTW "pwm0/pwm1" as "state" is confuse, but I understand this is how the PCA9552 
> > datasheet describes it.
> >
> > > > +
> > > >    static uint8_t pca9552_pin_get_config(PCA9552State *s, int pin)
> > > >    {
> > > >        uint8_t reg   = PCA9552_LS0 + (pin / 4);
> > > > @@ -169,6 +173,84 @@ static int pca9552_event(I2CSlave *i2c, enum i2c_event 
> > > > event)
> > > >        return 0;
> > > >    }
> > > >    +static void pca9552_get_led(Object *obj, Visitor *v, const char *name,
> > > > +                            void *opaque, Error **errp)
> > > > +{
> > > > +    PCA9552State *s = PCA9552(obj);
> > > > +    int led, rc, reg;
> > > > +    char *str;
> > > > +    uint8_t state;
> > > > +
> > > > +    rc = sscanf(name, "led%2d", &led);
> > > > +    if (rc != 1) {
> > > > +        error_setg(errp, "%s: error reading %s", __func__, name);
> > > > +        return;
> > > > +    }
> > > > +    if (led < 0 || led > s->nr_leds) {
> > > > +        error_setg(errp, "%s invalid led %s", __func__, name);
> > > > +        return;
> > > > +    }
> > > > +    /*
> > > > +     * Get the LSx register as the qom interface should expose the device
> > > > +     * state, not the modeled 'input line' behaviour which would come from
> > > > +     * reading the INPUTx reg
> > > > +     */
> > > > +    reg = PCA9552_LS0 + led / 4;
> > > > +    state = (pca9552_read(s, reg) >> (led % 8)) & 0x3;
> > >
> > > Could we add accessors to extract the register fields and to clarify
> > > the layout ?
> > >
> > > > +    str = g_strdup(led_state[state]);
> > > > +    visit_type_str(v, name, &str, errp);
> > > > +}
> > > > +
> > > > +/*
> > > > + * Return an LED selector register value based on an existing one, with
> > > > + * the appropriate 2-bit state value set for the given LED number (0-3).
> > > > + */
> > > > +static inline uint8_t pca955x_ledsel(uint8_t oldval, int led_num, int state)
> > > > +{
> > > > +        return (oldval & (~(0x3 << (led_num << 1)))) |
> > > > +                ((state & 0x3) << (led_num << 1));
> > > > +}
> > > > +
> > > > +static void pca9552_set_led(Object *obj, Visitor *v, const char *name,
> > > > +                            void *opaque, Error **errp)
> > > > +{
> > > > +    PCA9552State *s = PCA9552(obj);
> > > > +    Error *local_err = NULL;
> > > > +    int led, rc, reg, val;
> > > > +    uint8_t state;
> > > > +    char *state_str;
> > > > +
> > > > +    visit_type_str(v, name, &state_str, &local_err);
> > > > +    if (local_err) {
> > > > +        error_propagate(errp, local_err);
> > > > +        return;
> > > > +    }
> > > > +    rc = sscanf(name, "led%2d", &led);
> > > > +    if (rc != 1) {
> > > > +        error_setg(errp, "%s: error reading %s", __func__, name);
> > > > +        return;
> > > > +    }
> > > > +    if (led < 0 || led > s->nr_leds) {
> > > > +        error_setg(errp, "%s invalid led %s", __func__, name);
> > > > +        return;
> > > > +    }
> > > > +
> > > > +    for (state = 0; state < ARRAY_SIZE(led_state); state++) {
> > > > +        if (!strcmp(state_str, led_state[state])) {
> > > > +            break;
> > > > +        }
> > > > +    }
> > > > +    if (state >= ARRAY_SIZE(led_state)) {
> > > > +        error_setg(errp, "%s invalid led state %s", __func__, state_str);
> > > > +        return;
> > > > +    }
> > > > +
> > > > +    reg = PCA9552_LS0 + led / 4;
> > > > +    val = pca9552_read(s, reg);
> > > > +    val = pca955x_ledsel(val, led % 4, state);
> > > > +    pca9552_write(s, reg, val);
> > > > +}
> > > > +
> > > >    static const VMStateDescription pca9552_vmstate = {
> > > >        .name = "PCA9552",
> > > >        .version_id = 0,
> > > > @@ -204,6 +286,7 @@ static void pca9552_reset(DeviceState *dev)
> > > >    static void pca9552_initfn(Object *obj)
> > > >    {
> > > >        PCA9552State *s = PCA9552(obj);
> > > > +    int led;
> > > >          /* If support for the other PCA955X devices are implemented, these
> > > >         * constant values might be part of class structure describing the
> > > > @@ -211,6 +294,14 @@ static void pca9552_initfn(Object *obj)
> > > >         */
> > > >        s->max_reg = PCA9552_LS3;
> > > >        s->nr_leds = 16;
> > > > +
> > > > +    for (led = 0; led < s->nr_leds; led++) {
> > > > +        char *name;
> > > > +
> > > > +        name = g_strdup_printf("led%d", led);
> > > > +        object_property_add(obj, name, "bool", pca9552_get_led, 
> > > > pca9552_set_led,
> > > > +                            NULL, NULL, NULL);
> > >
> > > It misses a :
> > >
> > >      g_free(name)
> > >
> > > C.
> > >
> > > > +    }
> > > >    }
> > > >      static void pca9552_class_init(ObjectClass *klass, void *data)