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hw/arm/armv7m: Handle disconnected clock inputs 

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 <git@rpls.de>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220208171643.3486277-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2022-02-08 17:16:43 +00:00
parent e117e9748f
commit 542e87c7a2
1 changed files with 22 additions and 4 deletions
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26
hw/arm/armv7m.c
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@ -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);