Re: [PATCH v4 7/8] hw/misc/pca9552: Trace GPIO change events

[Philippe Mathieu-Daudé]

On 6/22/20 9:01 AM, Cédric Le Goater wrote:
> On 6/21/20 12:58 AM, Philippe Mathieu-Daudé wrote:
>> Emit a trace event when a GPIO change its state.
> 
> I understand now why you need 'pin_status'. 
> 
> We could compute 'pin_status' and 'pin_changed' in routine 
> pca9552_update_pin_input() when updating the PCA9552_INPUT0/1 
> register values and pass them to pca9552_display_pins_status()
> or something like that.

Good idea, thanks!

> 
> Maybe add two different display routines also. 
>  
>>
>> Example booting obmc-phosphor-image:
>>
>>   $ qemu-system-arm -M witherspoon-bmc -trace pca9552_gpio_change
>>   1592690552.687372:pca9552_gpio_change pca1 GPIO id:0 status: 0 -> 1
>>   1592690552.690169:pca9552_gpio_change pca1 GPIO id:1 status: 0 -> 1
>>   1592690552.691673:pca9552_gpio_change pca1 GPIO id:2 status: 0 -> 1
>>   1592690552.696886:pca9552_gpio_change pca1 GPIO id:3 status: 0 -> 1
>>   1592690552.698614:pca9552_gpio_change pca1 GPIO id:13 status: 0 -> 1
>>   1592690552.699833:pca9552_gpio_change pca1 GPIO id:14 status: 0 -> 1
>>   1592690552.700842:pca9552_gpio_change pca1 GPIO id:15 status: 0 -> 1
>>   1592690683.841921:pca9552_gpio_change pca1 GPIO id:14 status: 1 -> 0
>>   1592690683.861660:pca9552_gpio_change pca1 GPIO id:14 status: 0 -> 1
>>   1592690684.371460:pca9552_gpio_change pca1 GPIO id:14 status: 1 -> 0
>>   1592690684.882115:pca9552_gpio_change pca1 GPIO id:14 status: 0 -> 1
>>   1592690685.391411:pca9552_gpio_change pca1 GPIO id:14 status: 1 -> 0
>>   1592690685.901391:pca9552_gpio_change pca1 GPIO id:14 status: 0 -> 1
>>   1592690686.411678:pca9552_gpio_change pca1 GPIO id:14 status: 1 -> 0
>>   1592690686.921279:pca9552_gpio_change pca1 GPIO id:14 status: 0 -> 1
>>
>> 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
>>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>>  hw/misc/pca9552.c    | 15 +++++++++++++++
>>  hw/misc/trace-events |  1 +
>>  2 files changed, 16 insertions(+)
>>
>> diff --git a/hw/misc/pca9552.c b/hw/misc/pca9552.c
>> index f0d435e310..85557b78d9 100644
>> --- a/hw/misc/pca9552.c
>> +++ b/hw/misc/pca9552.c
>> @@ -60,6 +60,21 @@ static void pca9552_display_pins_status(PCA9552State *s)
>>          buf[i] = '\0';
>>          trace_pca9552_gpio_status(s->description, buf);
>>      }
>> +    if (trace_event_get_state_backends(TRACE_PCA9552_GPIO_CHANGE)) {
>> +        for (i = 0; i < s->nr_leds; i++) {
>> +            if (extract32(pins_changed, i, 1)) {
>> +                unsigned new_state = extract32(pins_status, i, 1);
>> +
>> +                /*
>> +                 * We display the state using the PCA logic ("active-high").
>> +                 * This is not the state of the LED, which signal might be
>> +                 * wired "active-low" on the board.
>> +                 */
>> +                trace_pca9552_gpio_change(s->description, i,
>> +                                          !new_state, new_state);
>> +            }
>> +        }
>> +    }
>>  }
>>  
>>  static void pca9552_update_pin_input(PCA9552State *s)
>> diff --git a/hw/misc/trace-events b/hw/misc/trace-events
>> index 7630e59652..805d2110e0 100644
>> --- a/hw/misc/trace-events
>> +++ b/hw/misc/trace-events
>> @@ -209,3 +209,4 @@ grlib_apb_pnp_read(uint64_t addr, uint32_t value) "APB 
>> PnP read addr:0x%03"PRIx6
>>  
>>  # pca9552.c
>>  pca9552_gpio_status(const char *description, const char *buf) "%s GPIOs 
>> 0-15 [%s]"
>> +pca9552_gpio_change(const char *description, unsigned id, unsigned 
>> prev_state, unsigned current_state) "%s GPIO id:%u status: %u -> %u"
>>
> 
>