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


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] misc/pca9552: Add qom set and get
Date: Tue, 19 Nov 2019 18:57:16 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1

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)









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