On Wednesday, June 14, 2017 01:59:09 PM Lv Zheng wrote: > The EC event IRQ (SCI_EVT) can only be handled by submitting QR_EC. As the > EC driver handles SCI_EVT in a workqueue, after SCI_EVT is flagged and > before QR_EC is submitted, there is a period risking IRQ storming. EC IRQ > must be masked for this period but linux EC driver never does so. > > No end user notices the IRQ storming and no developer fixes this known > issue because: > 1. the EC IRQ is always edge triggered GPE, and > 2. the kernel can execute no-op EC IRQ handler very fast. > For edge triggered EC GPE platforms, it is only reported of post-resume EC > event lost issues, there won't be an IRQ storming. For level triggered EC > GPE platforms, fortunately the kernel is always fast enough to execute such > a no-op EC IRQ handler so that the IRQ handler won't be accumulated to > starve the task contexts, causing a real IRQ storming. > > But the IRQ storming actually can still happen when: > 1. the EC IRQ performs like level triggered GPE, and > 2. the kernel EC debugging log is turned on but the console is slow enough. > There are more and more platforms using EC GPE as wake GPE where the EC GPE > is likely designed as level triggered. Then when EC debugging log is > enabled, the EC IRQ handler is no longer a no-op but dumps IRQ status to > the consoles. If the consoles are slow enough, the EC IRQs can arrive much > faster than executing the handler. Finally the accumulated EC event IRQ > handlers starve the task contexts, causing the IRQ storming to occur, and > the kernel hangs can be observed during boot/resume. > > See link #1 for reference, however the bug link can only be accessed by > priviledged Intel users. > > This patch fixes this issue by masking EC IRQ for this period: > 1. begins when there is an SCI_EVT IRQ pending, and > 2. ends when there is a QR_EC completed (SCI_EVT acknowledged). > > Link: https://jira01.devtools.intel.com/browse/LCK-4004 [#1] > Tested-by: Wang Wendy <wendy.wang@xxxxxxxxx> > Tested-by: Feng Chenzhou <chenzhoux.feng@xxxxxxxxx> > Signed-off-by: Lv Zheng <lv.zheng@xxxxxxxxx> I've applied this and the [2/3], but I'm not sure about the [3/3]. I'll reply to that patch. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
