RPi-B Add MULTIDELAY

[manu]

Summary

Add MULTIDELAY for RPI-B

Test Plan

Tested on RPI-B

[imp]

Modulo one small Q, this looks good to me.

sys/arm/broadcom/bcm2835/bcm2835_machdep.c

132 ↗

(On Diff #20775)

Do we know this platform has 200 cycles per us?

[manu]

In D8062#166787, @imp wrote:

Modulo one small Q, this looks good to me.

No idea, that was the number used before so I simply re-used it.

[imp]

In D8062#166794, @manu wrote:

In D8062#166787, @imp wrote:

Modulo one small Q, this looks good to me.

No idea, that was the number used before so I simply re-used it.

Perhaps we should see, since it is used here:

static void
platform_delay(int usec, void *arg __unused)
{

int counts;

for (; usec > 0; usec--)
        for (counts = plat_obj->cls->delay_count; counts > 0; counts--)
                /*
                 * Prevent the compiler from optimizing
                 * out the loop
                 */
                cpufunc_nullop();

}

[manu]

In D8062#166796, @imp wrote:

In D8062#166794, @manu wrote:

In D8062#166787, @imp wrote:

Modulo one small Q, this looks good to me.

No idea, that was the number used before so I simply re-used it.

Perhaps we should see, since it is used here:

static void
platform_delay(int usec, void *arg __unused)
{

int counts;

for (; usec > 0; usec--)
        for (counts = plat_obj->cls->delay_count; counts > 0; counts--)
                /*
                 * Prevent the compiler from optimizing
                 * out the loop
                 */
                cpufunc_nullop();

}

100 seems accurate enough.
But the platform bits for delay seems broken, the delay_count stays at 0.

[andrew]

sys/arm/broadcom/bcm2835/bcm2835_machdep.c

132 ↗

(On Diff #20775)

We currently lack a way to measure this. It would need someone to think about how to do this across the different timers.