From 542e87c7a2d90076b07611987fd3d789865e5ea1 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 8 Feb 2022 17:16:43 +0000 Subject: hw/arm/armv7m: Handle disconnected clock inputs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In the armv7m object, handle clock inputs that aren't connected. This is always an error for 'cpuclk'. For 'refclk' it is OK for this to be disconnected, but we need to handle it by not trying to connect a sourceless-clock to the systick device. This fixes a bug where on the mps2-an521 and similar boards (which do not have a refclk) the systick device incorrectly reset with SYST_CSR.CLKSOURCE 0 ("use refclk") rather than 1 ("use CPU clock"). Cc: qemu-stable@nongnu.org Reported-by: Richard Petri Signed-off-by: Peter Maydell Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Richard Henderson Message-id: 20220208171643.3486277-1-peter.maydell@linaro.org --- hw/arm/armv7m.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c index ceb76df..41cfca0 100644 --- a/hw/arm/armv7m.c +++ b/hw/arm/armv7m.c @@ -284,6 +284,12 @@ static void armv7m_realize(DeviceState *dev, Error **errp) return; } + /* cpuclk must be connected; refclk is optional */ + if (!clock_has_source(s->cpuclk)) { + error_setg(errp, "armv7m: cpuclk must be connected"); + return; + } + memory_region_add_subregion_overlap(&s->container, 0, s->board_memory, -1); s->cpu = ARM_CPU(object_new_with_props(s->cpu_type, OBJECT(s), "cpu", @@ -420,8 +426,18 @@ static void armv7m_realize(DeviceState *dev, Error **errp) &s->sysreg_ns_mem); } - /* Create and map the systick devices */ - qdev_connect_clock_in(DEVICE(&s->systick[M_REG_NS]), "refclk", s->refclk); + /* + * Create and map the systick devices. Note that we only connect + * refclk if it has been connected to us; otherwise the systick + * device gets the wrong answer for clock_has_source(refclk), because + * it has an immediate source (the ARMv7M's clock object) but not + * an ultimate source, and then it won't correctly auto-select the + * CPU clock as its only possible clock source. + */ + if (clock_has_source(s->refclk)) { + qdev_connect_clock_in(DEVICE(&s->systick[M_REG_NS]), "refclk", + s->refclk); + } qdev_connect_clock_in(DEVICE(&s->systick[M_REG_NS]), "cpuclk", s->cpuclk); if (!sysbus_realize(SYS_BUS_DEVICE(&s->systick[M_REG_NS]), errp)) { return; @@ -438,8 +454,10 @@ static void armv7m_realize(DeviceState *dev, Error **errp) */ object_initialize_child(OBJECT(dev), "systick-reg-s", &s->systick[M_REG_S], TYPE_SYSTICK); - qdev_connect_clock_in(DEVICE(&s->systick[M_REG_S]), "refclk", - s->refclk); + if (clock_has_source(s->refclk)) { + qdev_connect_clock_in(DEVICE(&s->systick[M_REG_S]), "refclk", + s->refclk); + } qdev_connect_clock_in(DEVICE(&s->systick[M_REG_S]), "cpuclk", s->cpuclk); -- cgit v1.1