[openwrt/openwrt] realtek: 6.6: copy patch 302-clocksource-add-otto-driver

[LEDE Commits]

svanheule pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/955d6b41f1b0b08182c111bd35a39871539b91ae

commit 955d6b41f1b0b08182c111bd35a39871539b91ae
Author: Markus Stockhausen <markus.stockhausen at gmx.de>
AuthorDate: Sun Aug 11 08:34:41 2024 -0400

    realtek: 6.6: copy patch 302-clocksource-add-otto-driver
    
    Copy the patch file to 6.6
    
    Signed-off-by: Markus Stockhausen <markus.stockhausen at gmx.de>
---
 .../302-clocksource-add-otto-driver.patch          | 93 ++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/target/linux/realtek/patches-6.6/302-clocksource-add-otto-driver.patch b/target/linux/realtek/patches-6.6/302-clocksource-add-otto-driver.patch
new file mode 100644
index 0000000000..63a5050ebb
--- /dev/null
+++ b/target/linux/realtek/patches-6.6/302-clocksource-add-otto-driver.patch
@@ -0,0 +1,93 @@
+From 3cc8011171186d906c547bc6f0c1f8e350edc7cf Mon Sep 17 00:00:00 2001
+From: Markus Stockhausen <markus.stockhausen at gmx.de>
+Date: Mon, 3 Oct 2022 14:45:21 +0200
+Subject: [PATCH] realtek: resurrect timer driver
+
+Now that we provide a clock driver for the Reltek SOCs the CPU frequency might
+change on demand. This has direct visible effects during operation
+
+- the CEVT 4K timer is no longer a stable clocksource
+- after CPU frequencies changes time calculation works wrong
+- sched_clock falls back to kernel default interval (100 Hz)
+- timestamps in dmesg have only 2 digits left
+
+[    0.000000] sched_clock: 32 bits at 100 Hz, resolution 10000000ns, wraps ...
+[    0.060000] pid_max: default: 32768 minimum: 301
+[    0.070000] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
+[    0.070000] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
+[    0.080000] dyndbg: Ignore empty _ddebug table in a CONFIG_DYNAMIC_DEBUG_CORE build
+[    0.090000] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, ...
+
+Looking around where we can start the CEVT timer for RTL930X is a good basis.
+Initially it was developed as a clocksource driver for the broken timer in that
+specific SOC series. Afterwards it was shifted around to the CEVT location,
+got SMP enablement and lost its clocksource feature. So we at least have
+something to copy from. As the timers on these devices are well understood
+the implementation follows this way:
+
+- leave the RTL930X implementation as is
+- provide a new driver for RTL83XX devices only
+- swap RTL930X driver at a later time
+
+Like the clock driver this patch contains a self contained module that is SOC
+independet and already provides full support for the RTL838X, RTL839X and
+RTL930X devices. Some of the new (or reestablished) features are:
+
+- simplified initialization routines
+- SMP setup with CPU hotplug framework
+- derived from LXB clock speed
+- supplied clocksource
+- dedicated register functions for better readability
+- documentation about some caveats
+
+Signed-off-by: Markus Stockhausen <markus.stockhausen at gmx.de>
+[remove unused header includes, remove old CONFIG_MIPS dependency, add
+REALTEK_ prefix to driver symbol]
+Signed-off-by: Sander Vanheule <sander at svanheule.net>
+
+---
+ drivers/clocksource/Kconfig                   | 12 +++
+ drivers/clocksource/Makefile                  |  1 +
+ include/linux/cpuhotplug.h                    |  1 +
+ 3 files changed, 14 insertions(+)
+
+--- a/drivers/clocksource/Kconfig
++++ b/drivers/clocksource/Kconfig
+@@ -127,6 +127,17 @@ config RDA_TIMER
+ 	help
+ 	  Enables the support for the RDA Micro timer driver.
+ 
++config REALTEK_OTTO_TIMER
++	bool "Clocksource/timer for the Realtek Otto platform"
++	select COMMON_CLK
++	select TIMER_OF
++	help
++	  This driver adds support for the timers found in the Realtek RTL83xx
++	  and RTL93xx SoCs series. This includes chips such as RTL8380, RTL8381
++	  and RTL832, as well as chips from the RTL839x series, such as RTL8390
++	  RT8391, RTL8392, RTL8393 and RTL8396 and chips of the RTL930x series
++	  such as RTL9301, RTL9302 or RTL9303.
++
+ config SUN4I_TIMER
+ 	bool "Sun4i timer driver" if COMPILE_TEST
+ 	depends on HAS_IOMEM
+--- a/drivers/clocksource/Makefile
++++ b/drivers/clocksource/Makefile
+@@ -58,6 +58,7 @@ obj-$(CONFIG_MILBEAUT_TIMER)	+= timer-mi
+ obj-$(CONFIG_SPRD_TIMER)	+= timer-sprd.o
+ obj-$(CONFIG_NPCM7XX_TIMER)	+= timer-npcm7xx.o
+ obj-$(CONFIG_RDA_TIMER)		+= timer-rda.o
++obj-$(CONFIG_REALTEK_OTTO_TIMER)	+= timer-rtl-otto.o
+ 
+ obj-$(CONFIG_ARC_TIMERS)		+= arc_timer.o
+ obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
+--- a/include/linux/cpuhotplug.h
++++ b/include/linux/cpuhotplug.h
+@@ -176,6 +176,7 @@ enum cpuhp_state {
+ 	CPUHP_AP_MARCO_TIMER_STARTING,
+ 	CPUHP_AP_MIPS_GIC_TIMER_STARTING,
+ 	CPUHP_AP_ARC_TIMER_STARTING,
++	CPUHP_AP_REALTEK_TIMER_STARTING,
+ 	CPUHP_AP_RISCV_TIMER_STARTING,
+ 	CPUHP_AP_CLINT_TIMER_STARTING,
+ 	CPUHP_AP_CSKY_TIMER_STARTING,