Hi,
On 26-12-16 12:07, Hans de Goede wrote:
Hi,
On 25-12-16 19:31, Len Brown wrote:
Is there a simple way to run a test to keep deep C-states
and instead disable part or all of i2c on this platform,
to see how much stability separating the two will buy us?
This should do the trick to completely disable i2c from the kernel
to the pmic, leaving the bus fully free for the punit:
diff --git a/drivers/i2c/busses/i2c-designware-baytrail.c b/drivers/i2c/busses/i2c-designware-baytrail.c
index 1590ad0..fe73271 100644
--- a/drivers/i2c/busses/i2c-designware-baytrail.c
+++ b/drivers/i2c/busses/i2c-designware-baytrail.c
@@ -140,6 +140,7 @@ int i2c_dw_eval_lock_support(struct dw_i2c_dev *dev)
if (shared_host) {
dev_info(dev->dev, "I2C bus managed by PUNIT\n");
+ return -ENODEV;
dev->acquire_lock = baytrail_i2c_acquire;
dev->release_lock = baytrail_i2c_release;
dev->pm_runtime_disabled = true;
Note that my patch only disabled deep C-states while the kernel
is accessing the pmic i2c bus, not all the time as most other
workarounds are doing.
Ok, some more very interesting input on this, from the bug
about the PUNIT semaphore issues on cherrytrail:
https://bugzilla.kernel.org/show_bug.cgi?id=155241#c37
"My device is a laptop with no USB charging or OTG. So, I'd tried only SDIO _ADR patch, i2c and axp288_fuel_gauge patches. Everything works well for upto 3 mins after boot, then the device freezes. I hadn't tried any drm patches BTW. Here's the log:
[drm:fw_domains_get [i915]] *ERROR* render: timed out waiting for forcewake ack request.
[drm:fw_domains_get [i915]] *MEDIA* render: timed out waiting for forcewake ack request.
[drm:fw_domains_get [i915]] *ERROR* render: timed out waiting for forcewake ack request.
[drm:fw_domains_get [i915]] *MEDIA* render: timed out waiting for forcewake ack request.
clocksource: timekeeping watchdog on CPU0: Marking clocksource 'tsc' as unstable because the skew is too large:
clocksource: 'refined-jiffies' wd_now: 10002ee30 wd_last: 10002edb8 mask: ffffffff
clocksource: 'tsc' cs_now: 16ac2c7744a cs_last: 16a8d9bd8f2 mask: ffffffffffffffff
clocksource: Switched to clocksource refined-jiffies
usb 1-2: reset high-speed USB device number 2 using xhci_hcd
i2c_designware 808622C1:06: punit semaphore timed out, resetting
i2c_designware 808622C1:06: PUNIT SEM: 2
i2c_designware 808622C1:06: couldn't acquire bus ownership
axp288_fuel_gauge axp288_fuel_gauge: axp288 reg read err:-110
axp288_fuel_gauge axp288_fuel_gauge: PWR STAT read failed:-110
usb 1-2: reset high-speed USB device number 2 using xhci_hcd
usb 1-2: reset high-speed USB device number 2 using xhci_hcd
usb 1-2: reset high-speed USB device number 2 using xhci_hcd
i2c_designware 808622C1:06: punit semaphore timed out, resetting
i2c_designware 808622C1:06: PUNIT SEM: 0
i2c_designware 808622C1:06: couldn't acquire bus ownership
axp288_fuel_gauge axp288_fuel_gauge: IIO channel read error: fffffffb, 0
power_supply axp288_fuel_gauge: driver failed to report `voltage_now' property: -5
***SYSTEM FREEZE***
If I blacklist axp288_fuel_gauge, then there were no errors."
So it seems that not only bad things happen when the punit tries to
change the cpu C-state while we're holding the pmic i2c bus
semaphore, but that similar bad things happen when the gpu code
tries to acquire / release a forcewake lock on the GPU while
we're accessing the pmic i2c bus.
This makes sense, the iosf_mbi code which is used by the
i2c bus semaphore code has this:
arch/x86/platform/intel/iosf_mbi.c:
int iosf_mbi_read(u8 port, u8 opcode, u32 offset, u32 *mdr)
{
u32 mcr, mcrx;
unsigned long flags;
int ret;
/* Access to the GFX unit is handled by GPU code */
if (port == BT_MBI_UNIT_GFX) {
WARN_ON(1);
return -EPERM;
}
...
}
So the i915 driver definitely is interacting with the punit
through the mailbox interface too...
I'll try to write a quick and dirty patch where the i915 code
simply calls intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
an extra time on probe, and ask the user who is seeing this to
test.
Regards,
Hans
code calls
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