kernel/linux.git/drivers/clocksource/arm_global_timer.c, branch v6.19.11

clocksource/drivers/arm_global_timer: Add auto-detection for initial prescaler values

2025-09-23T10:41:58+00:00

am43xx has a clock tree where the global timer clock is an indirect child of the CPU clock used for frequency scaling: dpll_mpu_ck -- CPU/cpufreq | v dpll_mpu_m2_ck -- divider | v mpu_periphclk -- fixed divider by 2 used for global timer When CPU frequency changes, the global timer's clock notifier rejects the change because the hardcoded prescaler (1 or 2) cannot accommodate the frequency range across all CPU OPPs (300, 600, 720, 800, 1000 MHz). Add platform-specific prescaler auto-detection to solve this issue: - am43xx: prescaler = 50 (calculated as initial_freq/GCD of all OPP freqs) This allows the timer to work across all CPU frequencies after the fixed divider by 2. Tested on am4372-idk-evm. - zynq-7000: prescaler = 2 (preserves previous Kconfig default) - Other platforms: prescaler = 1 (previous default) The Kconfig option now defaults to 0 (auto-detection) but can still override the auto-detected value when set to a non-zero value, preserving existing customization workflows. Signed-off-by: Markus Schneider-Pargmann Signed-off-by: Daniel Lezcano Tested-by: Kevin Hilman Tested-by: Patrice Chotard Tested-by: Judith Mendez Reviewed-by: Kevin Hilman Link: https://lore.kernel.org/r/20250819-topic-am43-arm-global-timer-v6-16-v2-1-6d082e2a5161@baylibre.com

clocksource/drivers/arm_global_timer: Remove clockevents shutdown call on offlining

2024-10-31T09:41:42+00:00

The clockevents core already detached and unregistered it at this stage. Signed-off-by: Frederic Weisbecker Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20241029125451.54574-7-frederic@kernel.org

clocksource/driver/arm_global_timer: Remove unnecessary ‘0’ values from err

2024-07-12T14:07:05+00:00

The 'err' variable is initialized whatever the code path, it is pointless to initialize it when it is declared. Signed-off-by: Li kunyu Link: https://lore.kernel.org/r/20240705052159.22235-1-kunyu@nfschina.com Signed-off-by: Daniel Lezcano

clocksource/drivers/arm_global_timer: Simplify prescaler register access

2024-02-26T09:07:25+00:00

Use GENMASK() to define the prescaler mask and make the whole driver use the mask (together with helpers such as FIELD_{GET,PREP,FIT}) instead of needing an additional shift and max value constant. Signed-off-by: Martin Blumenstingl Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240225151336.2728533-4-martin.blumenstingl@googlemail.com

clocksource/drivers/arm_global_timer: Guard against division by zero

2024-02-26T09:07:25+00:00

The result of the division of new_rate by gt_target_rate can be zero (if new_rate is smaller than gt_target_rate). Using that result as divisor without checking can result in a division by zero error. Guard against this by checking for a zero value earlier. While here, also change the psv variable to an unsigned long to make sure we don't overflow the datatype as all other types involved are also unsiged long. Signed-off-by: Martin Blumenstingl Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240225151336.2728533-3-martin.blumenstingl@googlemail.com

clocksource/drivers/arm_global_timer: Make gt_target_rate unsigned long

2024-02-26T09:07:25+00:00

Change the data type of gt_target_rate to unsigned long as this is what we get back from clk_get_rate(). Signed-off-by: Martin Blumenstingl Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240225151336.2728533-2-martin.blumenstingl@googlemail.com

clocksource: arm_global_timer: fix non-kernel-doc comment

2024-02-21T08:56:06+00:00

Use a common C comment "/*" instead of a kernel-doc marker "/**" to prevent kernel-doc warnings: arm_global_timer.c:92: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst * To ensure that updates to comparator value register do not set the arm_global_timer.c:92: warning: missing initial short description on line: * To ensure that updates to comparator value register do not set the Signed-off-by: Randy Dunlap Cc: Patrice Chotard Cc: linux-arm-kernel@lists.infradead.org Cc: Daniel Lezcano Cc: Thomas Gleixner Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240115053641.29129-1-rdunlap@infradead.org

clocksource/drivers/arm_global_timer: Remove stray tab

2024-02-18T23:48:54+00:00

Remove a stray tab in global_timer_of_register() which is different from the coding style in the rest of the driver. Signed-off-by: Martin Blumenstingl Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240218174138.1942418-3-martin.blumenstingl@googlemail.com

clocksource/drivers/arm_global_timer: Fix maximum prescaler value

2024-02-18T23:48:54+00:00

The prescaler in the "Global Timer Control Register bit assignments" is documented to use bits [15:8], which means that the maximum prescaler register value is 0xff. Fixes: 171b45a4a70e ("clocksource/drivers/arm_global_timer: Implement rate compensation whenever source clock changes") Signed-off-by: Martin Blumenstingl Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20240218174138.1942418-2-martin.blumenstingl@googlemail.com

clocksource/drivers/arm_global_timer: Remove duplicated argument in arm_global_timer

2021-06-16T15:33:04+00:00

Fix the following coccicheck warning: drivers/clocksource/arm_global_timer.c:107:4-23: duplicated argument to & or | Signed-off-by: Wan Jiabing Reviewed-by: Patrice Chotard Signed-off-by: Daniel Lezcano Link: https://lore.kernel.org/r/20210615115440.8881-1-wanjiabing@vivo.com