Recent changes to 205: Shouldn't __sync_synchronize() be used after writes and before IO reads ?

#205 Shouldn't __sync_synchronize() be used after writes and before IO reads ?

Ben Croston — Sat, 24 Sep 2022 10:23:21 -0000

assigned_to: Ben Croston

Shouldn't __sync_synchronize() be used after writes and before IO reads ?

David Rayna — Thu, 25 Aug 2022 19:31:43 -0000

Unless all CPUs do not queue writes or use caching for the gpio memory, shouldn't something like this be used, especially on multiple core CPUs ?

void output_gpio(int gpio, int value)
{
    int offset, shift;

    if (value) // value == HIGH
        offset = SET_OFFSET + (gpio/32);
    else       // value == LOW
       offset = CLR_OFFSET + (gpio/32);

    shift = (gpio%32);

    *(gpio_map+offset) = 1 << shift;
   __sync_synchronize();  // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
}

int input_gpio(int gpio)
{
   int offset, value, mask;

   offset = PINLEVEL_OFFSET + (gpio/32);
   mask = (1 << gpio%32);
   __sync_synchronize();  // <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   value = *(gpio_map+offset) & mask;
   return value;
}

Shouldn't __sync_synchronize() be used after writes and before IO reads ?

David Rayna — Thu, 25 Aug 2022 19:31:43 -0000

Ticket 205 has been modified: Shouldn't __sync_synchronize() be used after writes and before IO reads ?
Edited By: Ben Croston (croston)
Owner updated: None => 'croston'