[Intel-gfx] [PATCH v2 06/13] i2c: designware-baytrail: Disallow the CPU to enter C6 or C7 while holding the punit semaphore
Hans de Goede
hdegoede at redhat.com
Tue Jan 24 16:48:49 UTC 2017
On 01/24/2017 10:51 AM, Andy Shevchenko wrote:
> On Mon, 2017-01-23 at 22:09 +0100, Hans de Goede wrote:
>> On my cherrytrail tablet with axp288 pmic, just doing a bunch of
>> reads from the pmic, e.g. "i2cdump -y 14 0x34" would lookup the tablet
>> 1 - 3 runs guaranteed.
>> This seems to be causes by the cpu trying to enter C6 or C7 while we
>> the punit bus semaphore, at which point everything just hangs.
>> Avoid this by disallowing the CPU to enter C6 or C7 before acquiring
>> punit bus semaphore.
>> Changes in v5:
>> -Update the pm_qos for a latency of 0 *before* requesting the
>> instead of doing it while waiting for the request to be acked
> So, that's why you put to reset_semaphore() instead of
> baytrail_i2c_release(), right?
That is why the goto out gets introduced, baytrail_i2c_release()
and reset_semaphore() are functionally equivalent,
baytrail_i2c_release() does a bunch of argument error checking
and then calls reset_semaphore().
> I perhaps missed your answer to my comment about that.
>>> @@ -56,6 +57,8 @@ static void reset_semaphore(struct dw_i2c_dev
>> data &= ~PUNIT_SEMAPHORE_BIT;
>> if (iosf_mbi_write(BT_MBI_UNIT_PMC, MBI_REG_WRITE,
>> PUNIT_SEMAPHORE, data))
>> dev_err(dev->dev, "iosf failed to reset punit
>> semaphore during write\n");
>> + pm_qos_update_request(&dev->pm_qos, PM_QOS_DEFAULT_VALUE);
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