6.15-stable review patch. If anyone has any objections, please let me know.
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From: Zhang Rui rui.zhang@intel.com
commit 964209202ebe1569c858337441e87ef0f9d71416 upstream.
PL1 cannot be disabled on some platforms. The ENABLE bit is still set after software clears it. This behavior leads to a scenario where, upon user request to disable the Power Limit through the powercap sysfs, the ENABLE bit remains set while the CLAMPING bit is inadvertently cleared.
According to the Intel Software Developer's Manual, the CLAMPING bit, "When set, allows the processor to go below the OS requested P states in order to maintain the power below specified Platform Power Limit value."
Thus this means the system may operate at higher power levels than intended on such platforms.
Enhance the code to check ENABLE bit after writing to it, and stop further processing if ENABLE bit cannot be changed.
Reported-by: Srinivas Pandruvada srinivas.pandruvada@linux.intel.com Fixes: 2d281d8196e3 ("PowerCap: Introduce Intel RAPL power capping driver") Cc: All applicable stable@vger.kernel.org Signed-off-by: Zhang Rui rui.zhang@intel.com Link: https://patch.msgid.link/20250619071340.384782-1-rui.zhang@intel.com [ rjw: Use str_enabled_disabled() instead of open-coded equivalent ] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/powercap/intel_rapl_common.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
--- a/drivers/powercap/intel_rapl_common.c +++ b/drivers/powercap/intel_rapl_common.c @@ -340,12 +340,28 @@ static int set_domain_enable(struct powe { struct rapl_domain *rd = power_zone_to_rapl_domain(power_zone); struct rapl_defaults *defaults = get_defaults(rd->rp); + u64 val; int ret;
cpus_read_lock(); ret = rapl_write_pl_data(rd, POWER_LIMIT1, PL_ENABLE, mode); - if (!ret && defaults->set_floor_freq) + if (ret) + goto end; + + ret = rapl_read_pl_data(rd, POWER_LIMIT1, PL_ENABLE, false, &val); + if (ret) + goto end; + + if (mode != val) { + pr_debug("%s cannot be %s\n", power_zone->name, + str_enabled_disabled(mode)); + goto end; + } + + if (defaults->set_floor_freq) defaults->set_floor_freq(rd, mode); + +end: cpus_read_unlock();
return ret;