[PATCH v5 6/9] hw/misc/pca9552: Trace GPIO High/Low events

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

Add a trivial representation of the PCA9552 GPIOs.

Example booting obmc-phosphor-image:

  $ qemu-system-arm -M witherspoon-bmc -trace pca955x_gpio_status
  1592689902.327837:pca955x_gpio_status pca-unspecified GPIOs 0-15 [*...............]
  1592689902.329934:pca955x_gpio_status pca-unspecified GPIOs 0-15 [**..............]
  1592689902.330717:pca955x_gpio_status pca-unspecified GPIOs 0-15 [***.............]
  1592689902.331431:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****............]
  1592689902.332163:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........*..]
  1592689902.332888:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........**.]
  1592689902.333629:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........***]
  1592690032.793289:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........*.*]
  1592690033.303163:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........***]
  1592690033.812962:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........*.*]
  1592690034.323234:pca955x_gpio_status pca-unspecified GPIOs 0-15 [****.........***]
  1592690034.832922:pca955x_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>
---
 hw/misc/pca9552.c    | 39 +++++++++++++++++++++++++++++++++++++++
 hw/misc/trace-events |  3 +++
 2 files changed, 42 insertions(+)

diff --git a/hw/misc/pca9552.c b/hw/misc/pca9552.c
index d6d84c6451..13f5ed0da4 100644
--- a/hw/misc/pca9552.c
+++ b/hw/misc/pca9552.c
@@ -13,12 +13,14 @@
 #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"
 
 typedef struct PCA955xClass {
     /*< private >*/
@@ -49,6 +51,39 @@ static uint8_t pca955x_pin_get_config(PCA955xState *s, int pin)
     return extract32(s->regs[reg], shift, 2);
 }
 
+/* Return INPUT status (bit #N belongs to GPIO #N) */
+static uint16_t pca955x_pins_get_status(PCA955xState *s)
+{
+    return (s->regs[PCA9552_INPUT1] << 8) | s->regs[PCA9552_INPUT0];
+}
+
+static void pca955x_display_pins_status(PCA955xState *s,
+                                        uint16_t previous_pins_status)
+{
+    PCA955xClass *k = PCA955X_GET_CLASS(s);
+    uint16_t pins_status, pins_changed;
+    int i;
+
+    pins_status = pca955x_pins_get_status(s);
+    pins_changed = previous_pins_status ^ pins_status;
+    if (!pins_changed) {
+        return;
+    }
+    if (trace_event_get_state_backends(TRACE_PCA955X_GPIO_STATUS)) {
+        char *buf = g_newa(char, k->pin_count + 1);
+
+        for (i = 0; i < k->pin_count; i++) {
+            if (extract32(pins_status, i, 1)) {
+                buf[i] = '*';
+            } else {
+                buf[i] = '.';
+            }
+        }
+        buf[i] = '\0';
+        trace_pca955x_gpio_status(s->description, buf);
+    }
+}
+
 static void pca955x_update_pin_input(PCA955xState *s)
 {
     PCA955xClass *k = PCA955X_GET_CLASS(s);
@@ -98,6 +133,8 @@ static uint8_t pca955x_read(PCA955xState *s, uint8_t reg)
 
 static void pca955x_write(PCA955xState *s, uint8_t reg, uint8_t data)
 {
+    uint16_t pins_status;
+
     switch (reg) {
     case PCA9552_PSC0:
     case PCA9552_PWM0:
@@ -110,8 +147,10 @@ static void pca955x_write(PCA955xState *s, uint8_t reg, uint8_t data)
     case PCA9552_LS1:
     case PCA9552_LS2:
     case PCA9552_LS3:
+        pins_status = pca955x_pins_get_status(s);
         s->regs[reg] = data;
         pca955x_update_pin_input(s);
+        pca955x_display_pins_status(s, pins_status);
         break;
 
     case PCA9552_INPUT0:
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index 5561746866..9282c60dd9 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
+pca955x_gpio_status(const char *description, const char *buf) "%s GPIOs 0-15 [%s]"
-- 
2.21.3