[PATCH v3 3/4] hw/misc/pca9552: Trace LED On/Off events

[Philippe Mathieu-Daudé]

Add a trivial representation of the PCA9552 LEDs.

Example booting obmc-phosphor-image:

  $ qemu-system-arm -M witherspoon-bmc -trace pca9552_leds_status
  19286@1592574170.202791:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[*...............]
  19286@1592574170.203609:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[**..............]
  19286@1592574170.204102:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[***.............]
  19286@1592574170.204415:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****............]
  19286@1592574170.204758:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........*..]
  19286@1592574170.205070:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........**.]
  19286@1592574170.205380:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........***]
  19286@1592574235.384845:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........*.*]
  19286@1592574235.894049:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........***]
  19286@1592574236.404277:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........*.*]
  19286@1592574236.914644:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........***]
  19286@1592574237.424558:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........*.*]
  19286@1592574237.934580:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........***]
  19286@1592574238.444688:pca9552_leds_status 0x55dde47807c0 LEDs 0-15 
[****.........*.*]

We notice the LED #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 b2b9a5d9d4..4e171d88c6 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 leds_status; /* Holds latest INPUT0 & INPUT1 status */
     uint8_t max_reg;
     uint8_t nr_leds;
 } PCA9552State;
diff --git a/hw/misc/pca9552.c b/hw/misc/pca9552.c
index 00fa91b7f4..50c149077d 100644
--- a/hw/misc/pca9552.c
+++ b/hw/misc/pca9552.c
@@ -12,11 +12,13 @@
 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
+#include "qemu/bitops.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 PCA955X_LED_MAX 16
 
@@ -60,6 +62,32 @@ static void pca9552_update_pin_input(PCA9552State *s)
     }
 }
 
+static void pca9552_display_leds(PCA9552State *s)
+{
+    uint16_t leds_status, led_changed;
+    int i;
+
+    leds_status = (s->regs[PCA9552_INPUT1] << 8) | s->regs[PCA9552_INPUT0];
+    led_changed = s->leds_status ^ leds_status;
+    if (!led_changed) {
+        return;
+    }
+    s->leds_status = leds_status;
+    if (trace_event_get_state_backends(TRACE_PCA9552_LEDS_STATUS)) {
+        char buf[PCA9552_LED_COUNT + 1];
+
+        for (i = 0; i < s->nr_leds; i++) {
+            if (extract32(leds_status, i, 1)) {
+                buf[i] = '*';
+            } else {
+                buf[i] = '.';
+            }
+        }
+        buf[i] = '\0';
+        trace_pca9552_leds_status(s, buf);
+    }
+}
+
 static uint8_t pca9552_read(PCA9552State *s, uint8_t reg)
 {
     switch (reg) {
@@ -97,6 +125,7 @@ static void pca9552_write(PCA9552State *s, uint8_t reg, 
uint8_t data)
     case PCA9552_LS3:
         s->regs[reg] = data;
         pca9552_update_pin_input(s);
+        pca9552_display_leds(s);
         break;
 
     case PCA9552_INPUT0:
diff --git a/hw/misc/trace-events b/hw/misc/trace-events
index 5561746866..5d9505ad0f 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_leds_status(void *object, const char *buf) "%p LEDs 0-15 [%s]"
-- 
2.21.3