1. 28 6月, 2017 1 次提交
    • L
      ACPI: EC: Fix an EC event IRQ storming issue · 1ab69f27
      Lv Zheng 提交于
      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.
      
      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).
      Tested-by: NWang Wendy <wendy.wang@intel.com>
      Tested-by: NFeng Chenzhou <chenzhoux.feng@intel.com>
      Signed-off-by: NLv Zheng <lv.zheng@intel.com>
      Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      1ab69f27
  2. 23 6月, 2017 1 次提交
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