Cortex-M NVIC can have a different number of priority bits. Cortex-M0/M0+/M1 devices must use 2 or more bits, while devices based on ARMv7m and up must use 3 or more bits.
This adds a "num-prio-bits" property which will get sensible default values if unset (2 or 8 depending on the device). Unless a SOC specifies the number of bits to use, the previous behavior is maintained for backward compatibility. Signed-off-by: Samuel Tardieu <s...@rfc1149.net> Suggested-by: Anton Kochkov <anton.koch...@proton.me> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1122 Reviewed-by: Peter Maydell <peter.mayd...@linaro.org> --- hw/intc/armv7m_nvic.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c index 50f9a973a2..404a445138 100644 --- a/hw/intc/armv7m_nvic.c +++ b/hw/intc/armv7m_nvic.c @@ -2572,6 +2572,11 @@ static const VMStateDescription vmstate_nvic = { static Property props_nvic[] = { /* Number of external IRQ lines (so excluding the 16 internal exceptions) */ DEFINE_PROP_UINT32("num-irq", NVICState, num_irq, 64), + /* + * Number of the maximum priority bits that can be used. 0 means + * to use a reasonable default. + */ + DEFINE_PROP_UINT8("num-prio-bits", NVICState, num_prio_bits, 0), DEFINE_PROP_END_OF_LIST() }; @@ -2685,7 +2690,23 @@ static void armv7m_nvic_realize(DeviceState *dev, Error **errp) /* include space for internal exception vectors */ s->num_irq += NVIC_FIRST_IRQ; - s->num_prio_bits = arm_feature(&s->cpu->env, ARM_FEATURE_V7) ? 8 : 2; + if (s->num_prio_bits == 0) { + /* + * If left unspecified, use 2 bits by default on Cortex-M0/M0+/M1 + * and 8 bits otherwise. + */ + s->num_prio_bits = arm_feature(&s->cpu->env, ARM_FEATURE_V7) ? 8 : 2; + } else { + uint8_t min_prio_bits = + arm_feature(&s->cpu->env, ARM_FEATURE_V7) ? 3 : 2; + if (s->num_prio_bits < min_prio_bits || s->num_prio_bits > 8) { + error_setg(errp, + "num-prio-bits %d is outside " + "NVIC acceptable range [%d-8]", + s->num_prio_bits, min_prio_bits); + return; + } + } /* * This device provides a single memory region which covers the -- 2.42.0
