From 5deb9c789ae468a71a7c11c92d21769f7cbf68fa Mon Sep 17 00:00:00 2001 From: Yicong Yang Date: Tue, 11 Mar 2025 15:51:41 +0800 Subject: [PATCH] arch_topology: Support SMT control for OF based system On building the topology from the devicetree, we've already gotten the SMT thread number of each core. Update the largest SMT thread number and enable the SMT control by the end of topology parsing. The framework's SMT control provides two interface to the users through /sys/devices/system/cpu/smt/control (Documentation/ABI/testing/sysfs-devices-system-cpu): 1) enable SMT by writing "on" and disable by "off" 2) enable SMT by writing max_thread_number or disable by writing 1 Both method support to completely disable/enable the SMT cores so both work correctly for symmetric SMT platform and asymmetric platform with non-SMT and one type SMT cores like: core A: 1 thread core B: X (X!=1) threads Note that for a theoretically possible multiple SMT-X (X>1) core platform the SMT control is also supported as expected but only by writing the "on/off" method. Reviewed-by: Pierre Gondois Reviewed-by: Dietmar Eggemann Signed-off-by: Yicong Yang Reviewed-by: Jonathan Cameron Reviewed-by: Sudeep Holla Link: https://lore.kernel.org/r/20250311075143.61078-3-yangyicong@huawei.com Signed-off-by: Catalin Marinas --- drivers/base/arch_topology.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 3ebe77566788b..d409d323ee647 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -506,6 +507,10 @@ core_initcall(free_raw_capacity); #endif #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV) + +/* Used to enable the SMT control */ +static unsigned int max_smt_thread_num = 1; + /* * This function returns the logic cpu number of the node. * There are basically three kinds of return values: @@ -565,6 +570,8 @@ static int __init parse_core(struct device_node *core, int package_id, i++; } while (1); + max_smt_thread_num = max_t(unsigned int, max_smt_thread_num, i); + cpu = get_cpu_for_node(core); if (cpu >= 0) { if (!leaf) { @@ -677,6 +684,17 @@ static int __init parse_socket(struct device_node *socket) if (!has_socket) ret = parse_cluster(socket, 0, -1, 0); + /* + * Reset the max_smt_thread_num to 1 on failure. Since on failure + * we need to notify the framework the SMT is not supported, but + * max_smt_thread_num can be initialized to the SMT thread number + * of the cores which are successfully parsed. + */ + if (ret) + max_smt_thread_num = 1; + + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); + return ret; }