It is quite common for a clock tree to involve possibly programmable
clock multipliers or dividers, where the frequency of a clock is for
instance divided by 8 to produce a slower clock to feed to a
particular device.
Currently we provide no convenient mechanism for modelling this. You
can implement it by having an input Clock and an output Clock, and
manually setting the period of the output clock in the period-changed
callback of the input clock, but that's quite clunky.
This patch adds support in the Clock objects themselves for setting a
multiplier or divider. The effect of setting this on a clock is that
when the clock's period is changed, all the children of the clock are
set to period * multiplier / divider, rather than being set to the
same period as the parent clock.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alexandre Iooss <erdnaxe@crans.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Damien Hedde <damien.hedde@greensocs.com>
Message-id: 20210812093356.1946-10-peter.maydell@linaro.org
Add a clock_ns_to_ticks() function which does the opposite of
clock_ticks_to_ns(): given a duration in nanoseconds, it returns the
number of clock ticks that would happen in that time. This is useful
for devices that have a free running counter register whose value can
be calculated when it is read.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210219144617.4782-4-peter.maydell@linaro.org
Add a new callback event type ClockPreUpdate, which is called on
period changes before the period is updated.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Hao Wu <wuhaotsh@google.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210219144617.4782-3-peter.maydell@linaro.org
The Clock framework allows users to specify a callback which is
called after the clock's period has been updated. Some users need to
also have a callback which is called before the clock period is
updated.
As the first step in adding support for notifying Clock users on
pre-update events, add an argument to the ClockCallback to specify
what event is being notified, and add an argument to the various
functions for registering a callback to specify which events are
of interest to that callback.
Note that the documentation update renders correct the previously
incorrect claim in 'Adding a new clock' that callbacks "will be
explained in a following section".
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210219144617.4782-2-peter.maydell@linaro.org
Add a function for checking whether a clock has a source. This is
useful for devices which have input clocks that must be wired up by
the board as it allows them to fail in realize rather than ploughing
on with a zero-period clock.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20210128114145.20536-3-peter.maydell@linaro.org
Message-id: 20210121190622.22000-3-peter.maydell@linaro.org
It's common to want to print a human-readable indication of a clock's
frequency. Provide a utility function in the clock API to return a
string which is a displayable representation of the frequency,
and use it in qdev-monitor.c.
Before:
(qemu) info qtree
[...]
dev: xilinx,zynq_slcr, id ""
clock-in "ps_clk" freq_hz=3.333333e+07
mmio 00000000f8000000/0000000000001000
After:
dev: xilinx,zynq_slcr, id ""
clock-in "ps_clk" freq_hz=33.3 MHz
mmio 00000000f8000000/0000000000001000
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201215150929.30311-5-peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Remove the now-unused clock_get_ns() API and the CLOCK_PERIOD_TO_NS()
macro that only it was using.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201215150929.30311-4-peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
The clock_get_ns() API claims to return the period of a clock in
nanoseconds. Unfortunately since it returns an integer and a
clock's period is represented in units of 2^-32 nanoseconds,
the result is often an approximation, and calculating a clock
expiry deadline by multiplying clock_get_ns() by a number-of-ticks
is unacceptably inaccurate.
Introduce a new API clock_ticks_to_ns() which returns the number
of nanoseconds it takes the clock to make a given number of ticks.
This function can do the complete calculation internally and
will thus give a more accurate result.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Luc Michel <luc@lmichel.fr>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201215150929.30311-2-peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Add the documentation about the clock inputs and outputs in devices.
This is based on the original work of Frederic Konrad.
Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 20200406135251.157596-6-damien.hedde@greensocs.com
[PMM: Editing pass for minor grammar, style and Sphinx
formatting fixes]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
