From: Glenn Miles Date: Thu, 25 Sep 2025 20:17:45 +0000 (-0500) Subject: hw/ppc: Support for an IBM PPE42 CPU decrementer X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7197f6f7baf29fd76486920e5603e43b25880d3b;p=thirdparty%2Fqemu.git hw/ppc: Support for an IBM PPE42 CPU decrementer The IBM PPE42 processors support a 32-bit decrementer that can raise an external interrupt when DEC[0] transitions from a 0 to a -1 (a non-negative value to a negative value). It also continues decrementing even after this condition is met. The BookE timer is slightly different in that it raises an interrupt when the DEC value reaches 0 and stops decrementing at that point. Support a PPE42 version of the BookE timer by adding a new PPC_TIMER_PPE flag that has the timer code look for the transition from a non-negative value to a negative value and allows the value to continue decrementing. Signed-off-by: Glenn Miles Reviewed-by: Harsh Prateek Bora Signed-off-by: Harsh Prateek Bora Link: https://lore.kernel.org/r/20250925201758.652077-8-milesg@linux.ibm.com Message-ID: <20250925201758.652077-8-milesg@linux.ibm.com> --- diff --git a/hw/ppc/ppc_booke.c b/hw/ppc/ppc_booke.c index 3872ae28222..13403a56b1a 100644 --- a/hw/ppc/ppc_booke.c +++ b/hw/ppc/ppc_booke.c @@ -352,7 +352,12 @@ void ppc_booke_timers_init(PowerPCCPU *cpu, uint32_t freq, uint32_t flags) booke_timer = g_new0(booke_timer_t, 1); cpu->env.tb_env = tb_env; - tb_env->flags = flags | PPC_TIMER_BOOKE | PPC_DECR_ZERO_TRIGGERED; + if (flags & PPC_TIMER_PPE) { + /* PPE's use a modified version of the booke behavior */ + tb_env->flags = flags | PPC_DECR_UNDERFLOW_TRIGGERED; + } else { + tb_env->flags = flags | PPC_TIMER_BOOKE | PPC_DECR_ZERO_TRIGGERED; + } tb_env->tb_freq = freq; tb_env->decr_freq = freq; diff --git a/include/hw/ppc/ppc.h b/include/hw/ppc/ppc.h index 8a14d623f8c..cb51d704c6d 100644 --- a/include/hw/ppc/ppc.h +++ b/include/hw/ppc/ppc.h @@ -52,6 +52,7 @@ struct ppc_tb_t { #define PPC_DECR_UNDERFLOW_LEVEL (1 << 4) /* Decr interrupt active when * the most significant bit is 1. */ +#define PPC_TIMER_PPE (1 << 5) /* Enable PPE support */ uint64_t cpu_ppc_get_tb(ppc_tb_t *tb_env, uint64_t vmclk, int64_t tb_offset); void cpu_ppc_tb_init(CPUPPCState *env, uint32_t freq);