Hi,
On 10-12-16 15:53, Andy Shevchenko wrote:
+Cc: Len
Len, I think you would be interested by this.
Hans, thanks for the change!
You're welcome I ended up comparing the code in
i2c-dw_i2c-Ported-punit-locking-patch-from-MCG-kerne.patch from:
https://github.com/01org/ProductionKernelQuilts/tree/master/uefi/cht-m1stable/patches
against the mainline code while I was trying to fix the maddening
problem of the entire SoC hanging more or less as soon
as I tried to use the pmic i2c bus and there I found
some fiddling with pm_qos which let to this patch.
Most probably we will anticipate Len's ACK
on this one.
On Sat, 2016-12-10 at 15:19 +0100, Hans de Goede wrote:
On my cherrytrail tablet with axp288 pmic, just doing a bunch of
repeated
reads from the pmic, e.g. "i2cdump -y 14 0x34" would lookup the tablet
in
1 - 3 runs guaranteed.
This seems to be causes by the cpuidle / intel_idle driver trying to
change the C-state while we hold the punit bus semaphore, at which
point
everything just hangs.
Avoid this by forcing the CPU to C1 before acquiring the punit bus
semaphore.
Isn't it C0? C1 as far as I remember is halted state.
You're right, I will fix it.
@@ -33,6 +34,13 @@ static int get_sem(struct dw_i2c_dev *dev, u32
*sem)
u32 data;
int ret;
+ /*
+ * Force CPU to C1 state, otherwise if the cpuidle /
intel_idle
+ * driver tries to change the C state while we're holding the
+ * semaphore, the SoC hangs.
C0?
+ */
+ pm_qos_update_request(&dev->pm_qos, 0);
C1 is when you set 1 here, right?
I believe so, yes.
platform_device *pdev)
if (!dev->pm_runtime_disabled)
pm_runtime_disable(&pdev->dev);
+ if (dev->acquire_lock)
+ pm_qos_remove_request(&dev->pm_qos);
+
Perhaps you need to do this in -core.c. Otherwise you missed PCI case.
(Even with PCI enumerated host with ACPI-enabled firmware you may get
_SEM object present)
Currently only i2c-designware-plardrv.c calls i2c_dw_eval_lock_support()
which does the pm_qos_add_request, so I put it here to keep things
balanced.
Regards,
Hans
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