Re: [PATCH] intel_ips: quieten "power or thermal limit exceeded" messages

Jesse Barnes
2010-09-23T20:31:36Z

On Fri, 27 Aug 2010 19:21:44 -0700
Joe Perches <joe@perches.com> wrote:

> On Fri, 2010-08-27 at 20:12 -0300, Cesar Eduardo Barros wrote:
> > Em 27-08-2010 04:39, Joe Perches escreveu:
> > > On Thu, 2010-08-26 at 22:38 -0300, Cesar Eduardo Barros wrote:
> > >> - The first "MCP power limit exceeded" seems very bogus.
> > >> - What do you mean, core_power_limit is zero?
> > > I added a logging message whenever the turbo limits change
> > > and logging messages for power/temp on MCH for completeness.
> > > Maybe this will show something useful like when/how
> > > CPU power limit gets set to 0.
>
> > Running with it right now, did not help much:
> >
> > $ dmesg | fgrep 'intel ips'
> > intel ips 0000:00:1f.6: Warning: CPU TDP doesn't match expected value
> > (found 25, expected 35)
> > intel ips 0000:00:1f.6: PCI INT C -> GSI 18 (level, low) -> IRQ 18
> > intel ips 0000:00:1f.6: IPS driver initialized, MCP temp limit 65535
> > intel ips 0000:00:1f.6: MCP power limit 65535 exceeded: cpu:8058 +
> > mch:23392829
> > intel ips 0000:00:1f.6: CPU power limit 0 exceeded: 5675
> > intel ips 0000:00:1f.6: CPU power limit 0 exceeded: 6369
>
> I believe all these limits should always have non-zero values.
> So I still think you've hardware problems, but I suppose it
> could be the driver not reading the right registers or some
> such. It seems odd that the driver never printed a logging
> message for either of the polling or irq methods to read the
> device cpu and thermal limits.
>
> Jesse or any Intel folk, can you verify or suggest anything
> better?
>
> If cpu_power_limit, or any _limit, is not set perhaps changing
> the test style to verify limit and adding a printed_once alert
> for each 0 value limit. At least that'd shut up the continuous
> logging but at least give a notification message.
>
> if (limit) {
> if (measured_val > limit)
> dev_info(foo)
> } else
> dev_alert_once()
>
> Maybe something like this:
>
> drivers/platform/x86/intel_ips.c | 160 +++++++++++++++++++++++++++++++++-----
> 1 files changed, 140 insertions(+), 20 deletions(-)

Yes, we do need something like this. It turns out the BIOS can
optionally program several of these values, and we need to sanity check
them. If they're not valid (e.g. a core power limit of 0 or MCP temp
limit of 0xffff) we need to use the default values in the limit structs.

I think the programmed limits are valid if they're nonzero and less
than one of the available default limits. If they're not valid, we
should just use the default values. I was thinking something like the
below for MCP, but Joe you may want to just update your patch instead
since it's more complete.

Thanks,
--
Jesse Barnes, Intel Open Source Technology Center

diff --git a/drivers/platform/x86/intel_ips.c b/drivers/platform/x86/intel_ips.c
index 9024480..ec72e80 100644
--- a/drivers/platform/x86/intel_ips.c
+++ b/drivers/platform/x86/intel_ips.c
@@ -662,6 +662,17 @@ static bool mch_exceeded(struct ips_driver *ips)
return ret;
}

+static void clamp_mcp_temp_limit(struct ips_driver *ips)
+{
+ /*
+ * BIOS may or may not program an MCP limit. Clamp it to the
+ * lowest available value.
+ */
+ if (ips->mcp_temp_limit < ips->core_temp_limit ||
+ ips->mcp_temp_limit < ips->mch_temp_limit)
+ ips->mcp_temp_limit = min(ips->core_temp_limit, ips->mch_temp_limit);
+}
+
/**
* update_turbo_limits - get various limits & settings from regs
* @ips: IPS driver struct
@@ -686,6 +697,7 @@ static void update_turbo_limits(struct ips_driver *ips)
ips->mcp_temp_limit = thm_readw(THM_PTL);
ips->mcp_power_limit = thm_readw(THM_MPPC);

+ clamp_mcp_temp_limit(ips);
/* Ignore BIOS CPU vs GPU pref */
}

@@ -1155,6 +1167,7 @@ static irqreturn_t ips_irq_handler(int irq, void *arg)
STS_PTL_SHIFT;
ips->mcp_power_limit = (tc1 & STS_PPL_MASK) >>
STS_PPL_SHIFT;
+ clamp_mcp_temp_limit(ips);
spin_unlock(&ips->turbo_status_lock);

thm_writeb(THM_SEC, SEC_ACK);