On 5 November 2013 11:41, Jan Petrouš <jan.petr...@tieto.com> wrote:
> Linux kernel from version 3.4 requires CM_REFCNT register for sched timer
> for Integrator/CP board (integrator_defconfig).
>
> See
> http://infocenter.arm.com/help/topic/com.arm.doc.dui0138e/ch04s06s11.html
>
> Signed-off-by: Jan Petrous <jan.petr...@tieto.com>
Hi; thanks for this patch. (I have to wonder why on earth
people are still messing with kernel functionality for such
an ancient devboard :-)).
> diff --git a/hw/arm/integratorcp.c b/hw/arm/integratorcp.c
> index c44b2a4..f419764 100644
> --- a/hw/arm/integratorcp.c
> +++ b/hw/arm/integratorcp.c
> @@ -83,8 +83,11 @@ static uint64_t integratorcm_read(void *opaque, hwaddr
> offset,
> case 9: /* CM_INIT */
> return s->cm_init;
> case 10: /* CM_REFCT */
could you fix this comment to add the 'N' to CM_REFCNT while
you're changing this bit of code, please?
> - /* ??? High frequency timer. */
> - hw_error("integratorcm_read: CM_REFCT");
> + /* This register, CM_REFCNT, provides a 32-bit count value.
> + * The count increments at the fixed reference clock frequency of 24MHz
> + * and can be used as a real-time counter.
> + */
The indent here doesn't look right, I think you have
hardcoded tabs here rather than spaces. If you run your
patch through scripts/checkpatch.pl it should catch this
sort of mistake.
> + return muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), 24, 1000);
> case 12: /* CM_FLAGS */
> return s->cm_flags;
> case 14: /* CM_NVFLAGS */
The spec says that this register resets to zero, so I think
it would be good to implement that: put a uint32_t cm_refcnt_offset
in the IntegratorCMState struct, initialize it with the initial
value of muldiv64(etc) in integratorcm_init(), and then in
integratorcm_read() return (uint32_t)muldiv64(etc) - cm_refcnt_offset
for the register read.
(We don't actually implement a proper reset function in this device
at the moment, but putting in the offset field gives us a marker
for doing it right if/when we add a reset function later on.)
thanks
-- PMM
