[PATCH v4 5/8] hw/misc/pca9552: Trace GPIO High/Low events

[Philippe Mathieu-Daudé]

Add a trivial representation of the PCA9552 GPIOs.

Example booting obmc-phosphor-image:

  $ qemu-system-arm -M witherspoon-bmc -trace pca9552_gpio_status
  1592689902.327837:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[*...............]
  1592689902.329934:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[**..............]
  1592689902.330717:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[***.............]
  1592689902.331431:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****............]
  1592689902.332163:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........*..]
  1592689902.332888:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........**.]
  1592689902.333629:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........***]
  1592690032.793289:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........*.*]
  1592690033.303163:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........***]
  1592690033.812962:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........*.*]
  1592690034.323234:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........***]
  1592690034.832922:pca9552_gpio_status pca-unspecified GPIOs 0-15 
[****.........*.*]

We notice the GPIO #14 (front-power LED) starts to blink.

This LED is described in the witherspoon device-tree [*]:

  front-power {
      retain-state-shutdown;
      default-state = "keep";
      gpios = <&pca0 14 GPIO_ACTIVE_LOW>;
  };

[*] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts?id=b1f9be9392f0#n140

Suggested-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 include/hw/misc/pca9552.h |  1 +
 hw/misc/pca9552.c         | 29 +++++++++++++++++++++++++++++
 hw/misc/trace-events      |  3 +++
 3 files changed, 33 insertions(+)

diff --git a/include/hw/misc/pca9552.h b/include/hw/misc/pca9552.h
index c5be7f1c5e..755be2e8e5 100644
--- a/include/hw/misc/pca9552.h
+++ b/include/hw/misc/pca9552.h
@@ -26,6 +26,7 @@ typedef struct PCA9552State {
     uint8_t pointer;
 
     uint8_t regs[PCA9552_NR_REGS];
+    uint16_t pins_status; /* Holds latest INPUT0 & INPUT1 status */
     uint8_t max_reg;
     char *description; /* For debugging purpose only */
     uint8_t nr_leds;
diff --git a/hw/misc/pca9552.c b/hw/misc/pca9552.c
index 54ccdcf6d4..f0d435e310 100644
--- a/hw/misc/pca9552.c
+++ b/hw/misc/pca9552.c
@@ -12,12 +12,14 @@
 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
+#include "qemu/bitops.h"
 #include "hw/qdev-properties.h"
 #include "hw/misc/pca9552.h"
 #include "hw/misc/pca9552_regs.h"
 #include "migration/vmstate.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
+#include "trace.h"
 
 #define PCA9552_LED_ON   0x0
 #define PCA9552_LED_OFF  0x1
@@ -34,6 +36,32 @@ static uint8_t pca9552_pin_get_config(PCA9552State *s, int 
pin)
     return extract32(s->regs[reg], shift, 2);
 }
 
+static void pca9552_display_pins_status(PCA9552State *s)
+{
+    uint16_t pins_status, pins_changed;
+    int i;
+
+    pins_status = (s->regs[PCA9552_INPUT1] << 8) | s->regs[PCA9552_INPUT0];
+    pins_changed = s->pins_status ^ pins_status;
+    if (!pins_changed) {
+        return;
+    }
+    s->pins_status = pins_status;
+    if (trace_event_get_state_backends(TRACE_PCA9552_GPIO_STATUS)) {
+        char buf[PCA9552_PIN_COUNT + 1];
+
+        for (i = 0; i < s->nr_leds; i++) {
+            if (extract32(pins_status, i, 1)) {
+                buf[i] = '*';
+            } else {
+                buf[i] = '.';
+            }
+        }
+        buf[i] = '\0';
+        trace_pca9552_gpio_status(s->description, buf);
+    }
+}
+
 static void pca9552_update_pin_input(PCA9552State *s)
 {
     int i;
@@ -57,6 +85,7 @@ static void pca9552_update_pin_input(PCA9552State *s)
             break;
         }
     }
+    pca9552_display_pins_status(s);
 }
 
 static uint8_t pca9552_read(PCA9552State *s, uint8_t reg)
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index 5561746866..7630e59652 100644
--- a/hw/misc/trace-events
+++ b/hw/misc/trace-events
@@ -206,3 +206,6 @@ via1_rtc_cmd_pram_sect_write(int sector, int offset, int 
addr, int value) "secto
 # grlib_ahb_apb_pnp.c
 grlib_ahb_pnp_read(uint64_t addr, uint32_t value) "AHB PnP read 
addr:0x%03"PRIx64" data:0x%08x"
 grlib_apb_pnp_read(uint64_t addr, uint32_t value) "APB PnP read 
addr:0x%03"PRIx64" data:0x%08x"
+
+# pca9552.c
+pca9552_gpio_status(const char *description, const char *buf) "%s GPIOs 0-15 
[%s]"
-- 
2.21.3