Re: [Qemu-devel] [PATCH] nvic: Change NVIC to support ARMv6-M

[Stefan Hajnoczi <stefanha@gmail.com>]

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On Wed, Jul 11, 2018 at 02:33:14PM +0100, Peter Maydell wrote:
> On 11 July 2018 at 14:25, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> > On Tue, Jul 10, 2018 at 06:33:35PM +0300, Julia Suvorova via Qemu-devel wrote:
> >> The differences from ARMv7-M NVIC are:
> >>   * ARMv6-M only supports up to 32 external interrupts
> >>    (configurable feature already). The ICTR is reserved.
> >>   * Active Bit Register is reserved.
> >>   * ARMv6-M supports 4 priority levels against 256 in ARMv7-M.
> >>
> >> Signed-off-by: Julia Suvorova <jusual@mail.ru>
> >> ---
> >>  hw/intc/armv7m_nvic.c | 29 +++++++++++++++++++++++++----
> >>  1 file changed, 25 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> >> index 38aaf3dc8e..8545c87caa 100644
> >> --- a/hw/intc/armv7m_nvic.c
> >> +++ b/hw/intc/armv7m_nvic.c
> >> @@ -420,6 +420,10 @@ static void set_prio(NVICState *s, unsigned irq, bool secure, uint8_t prio)
> >>      assert(irq > ARMV7M_EXCP_NMI); /* only use for configurable prios */
> >>      assert(irq < s->num_irq);
> >>
> >> +    if (!arm_feature(&s->cpu->env, ARM_FEATURE_V7)) {
> >
> > ARMv8-M also has the NVIC:
> > https://static.docs.arm.com/ddi0553/a/DDI0553A_e_armv8m_arm.pdf
> >
> > Should arm_feature(&s->cpu->env, ARM_FEATURE_V6) be used instead of
> > !arm_feature(&s->cpu->env, ARM_FEATURE_V7)?
> 
> All of v6M, v7M and v8M cores will set ARM_FEATURE_V6, so
> testing on it doesn't distinguish them.

Okay.

Stefan

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