kernel/linux.git/drivers/clocksource/timer-stm32.c, branch v4.17.1

clocksource/drivers/stm32: Start the timer's counter sooner

2018-01-08T16:57:26+00:00

As we have a lot of timers on this platform, we can have potentially all the timers enabled in the DT, so we don't want to start the timer for every probe otherwise they will be running for nothing as only one will be used. Start the timer only when setting the mode or when the clocksource is enabled. Tested-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-20-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Add the timer delay callback

2018-01-08T16:57:26+00:00

Add the timer delay callback, that saves us ~90ms of boot time. Tested-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-19-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Add clocksource functionality

2018-01-08T16:57:26+00:00

The scene is set for the clocksource functionality, let's add it for this driver. Tested-by: Benjamin Gaignard Signed-off-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-18-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Factor out more of the clockevent code

2018-01-08T16:57:26+00:00

In order to prepare the clocksource code, let's factor out the clockevent code, split the prescaler and timer width code into separate functions. Tested-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-17-git-send-email-daniel.lezcano@linaro.org [ Small edits. ] Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Add oneshot mode

2018-01-08T16:57:26+00:00

The stm32 timer block is able to have a counter and a comparator. Instead of using the auto-reload register for periodic events, we switch to oneshot mode by using the comparator register. The timer is able to generate an interrupt when the counter overflows but we don't want that as this counter will be use as a clocksource in the next patches. So it is disabled by the UDIS bit of the control register. Tested-by: Benjamin Gaignard Signed-off-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-16-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Compute a prescaler value with a targeted rate

2018-01-08T16:57:25+00:00

The prescaler value is arbitrarily set to 1024 without any regard to the timer frequency. For 32-bit timers, there is no need to set a prescaler value as they wrap in an acceptable interval and give the opportunity to have precise timers on this platform. However, for 16-bit timers a prescaler value is needed if we don't want to wrap too often per second which is inefficient and adds more and more error margin. With a targeted clock of 10MHz, the 16 bits are precise enough whatever the timer frequency is as we will compute the prescaler. Tested-by: Benjamin Gaignard Signed-off-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-15-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Factor out the timer width sorting code

2018-01-08T16:57:25+00:00

In order to clarify and encapsulate the code for upcoming changes, move the timer width check into a function and add some documentation. Tested-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-14-git-send-email-daniel.lezcano@linaro.org [ Spelling fixes. ] Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Use the node name as timer name

2018-01-08T16:57:25+00:00

As there are different timers on the stm32, use the node name for the timer name in order to give the indication of which timer the kernel is using. /proc/timer_list gives all the information with the right name, otherwise we end up digging in the kernel log and /proc/interrupt to do the connection between the used timer. Tested-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-13-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Convert the driver to timer_of primitives

2018-01-08T16:57:25+00:00

Convert the driver to use the timer_of() helpers. This allows the removal of a custom private structure, factors out and simplifies the code. [Daniel Lezcano]: Respin against the critical fix patch and massaged the changelog. Tested-by: Benjamin Gaignard Signed-off-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1515418139-23276-12-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar

clocksource/drivers/stm32: Fix kernel panic with multiple timers

2018-01-08T16:57:25+00:00

The current code hides a couple of bugs: - The global variable 'clock_event_ddata' is overwritten each time the init function is invoked. This is fixed with a kmemdup() instead of assigning the global variable. That prevents a memory corruption when several timers are defined in the DT. - The clockevent's event_handler is NULL if the time framework does not select the clockevent when registering it, this is fine but the init code generates in any case an interrupt leading to dereference this NULL pointer. The stm32 timer works with shadow registers, a mechanism to cache the registers. When a change is done in one buffered register, we need to artificially generate an event to force the timer to copy the content of the register to the shadowed register. The auto-reload register (ARR) is one of the shadowed register as well as the prescaler register (PSC), so in order to force the copy, we issue an event which in turn leads to an interrupt and the NULL dereference. This is fixed by inverting two lines where we clear the status register before enabling the update event interrupt. As this kernel crash is resulting from the combination of these two bugs, the fixes are grouped into a single patch. Tested-by: Benjamin Gaignard Signed-off-by: Daniel Lezcano Acked-by: Benjamin Gaignard Cc: Alexandre Torgue Cc: Linus Torvalds Cc: Maxime Coquelin Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/1515418139-23276-11-git-send-email-daniel.lezcano@linaro.org Signed-off-by: Ingo Molnar