intel_idle: Introduce a helper for checking PC6

Introduce the skx_is_pc6_disabled() for checking if PC6 is disabled and
switch the following functions to use it:

 - skx_idle_state_table_update()
 - spr_idle_state_table_update()

At the same time, clean them up improving the commentary and moving it to
the function kernel-doc.

Purely a clean up, no functional changes intended.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20260425072532.358365-4-dedekind1@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 259013c246d904659cc4f55291f860e24541d1aa..def04b1ab35511b6dddbe796869074615a161023 100644 (file)
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -2079,12 +2079,13 @@ static void __init sklh_idle_state_table_update(void)
 }
 
 /**
- * skx_idle_state_table_update - Adjust the Sky Lake/Cascade Lake
- * idle states table.
+ * skx_is_pc6_disabled() - Check if PC6 is disabled in BIOS.
+ *
+ * Return: %true if PC6 is disabled, %false otherwise.
  */
-static void __init skx_idle_state_table_update(void)
+static bool __init skx_is_pc6_disabled(void)
 {
-       unsigned long long msr;
+       u64 msr;
 
        rdmsrq(MSR_PKG_CST_CONFIG_CONTROL, msr);
 
@@ -2095,35 +2096,34 @@ static void __init skx_idle_state_table_update(void)
         * 011b: C6 (retention)
         * 111b: No Package C state limits.
         */
-       if ((msr & SKX_PKG_CST_LIMIT_MASK) < SKX_PKG_CST_LIMIT_PC6) {
-               /*
-                * Uses the CC6 + PC0 latency and 3 times of
-                * latency for target_residency if the PC6
-                * is disabled in BIOS. This is consistent
-                * with how intel_idle driver uses _CST
-                * to set the target_residency.
-                */
+       return (msr & SKX_PKG_CST_LIMIT_MASK) < SKX_PKG_CST_LIMIT_PC6;
+}
+
+/**
+ * skx_idle_state_table_update - Adjust the SKX/CLX idle states table.
+ *
+ * Adjust Sky Lake or Cascade Lake Xeon idle states if PC6 is disabled in BIOS.
+ * Use the CC6 + PC0 latency and 3 times of that latency for target_residency.
+ * This is consistent with how the intel_idle driver uses _CST to set the
+ * target_residency.
+ */
+static void __init skx_idle_state_table_update(void)
+{
+       if (skx_is_pc6_disabled()) {
                skx_cstates[2].exit_latency = 92;
                skx_cstates[2].target_residency = 276;
        }
 }
 
 /**
- * spr_idle_state_table_update - Adjust Sapphire Rapids idle states table.
+ * spr_idle_state_table_update - Adjust Sapphire Rapids Xeon idle states table.
+ *
+ * By default, the C6 state assumes the worst-case scenario of package C6.
+ * However, if PC6 is disabled in BIOS, update the numbers to match core C6.
  */
 static void __init spr_idle_state_table_update(void)
 {
-       unsigned long long msr;
-
-       /*
-        * By default, the C6 state assumes the worst-case scenario of package
-        * C6. However, if PC6 is disabled, we update the numbers to match
-        * core C6.
-        */
-       rdmsrq(MSR_PKG_CST_CONFIG_CONTROL, msr);
-
-       /* Limit value 2 and above allow for PC6. */
-       if ((msr & SKX_PKG_CST_LIMIT_MASK) < SKX_PKG_CST_LIMIT_PC6) {
+       if (skx_is_pc6_disabled()) {
                spr_cstates[2].exit_latency = 190;
                spr_cstates[2].target_residency = 600;
        }