USB: EHCI cpufreq fix

[mirror_ubuntu-zesty-kernel.git] / drivers / usb / host / ehci-hcd.c

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 099aff64f5361de4cb87c25bb37e8f45d3afbd98..566badb05b348b258c3c93aa12e57041131ae929 100644 (file)
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -273,6 +273,58 @@ static void ehci_work(struct ehci_hcd *ehci);
 
 /*-------------------------------------------------------------------------*/
 
+#ifdef CONFIG_CPU_FREQ
+
+#include <linux/cpufreq.h>
+
+static void ehci_cpufreq_pause (struct ehci_hcd *ehci)
+{
+       unsigned long   flags;
+
+       spin_lock_irqsave(&ehci->lock, flags);
+       if (!ehci->cpufreq_changing++)
+               qh_inactivate_split_intr_qhs(ehci);
+       spin_unlock_irqrestore(&ehci->lock, flags);
+}
+
+static void ehci_cpufreq_unpause (struct ehci_hcd *ehci)
+{
+       unsigned long   flags;
+
+       spin_lock_irqsave(&ehci->lock, flags);
+       if (!--ehci->cpufreq_changing)
+               qh_reactivate_split_intr_qhs(ehci);
+       spin_unlock_irqrestore(&ehci->lock, flags);
+}
+
+/*
+ * ehci_cpufreq_notifier is needed to avoid MMF errors that occur when
+ * EHCI controllers that don't cache many uframes get delayed trying to
+ * read main memory during CPU frequency transitions.  This can cause
+ * split interrupt transactions to not be completed in the required uframe.
+ * This has been observed on the Broadcom/ServerWorks HT1000 controller.
+ */
+static int ehci_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
+                                void *data)
+{
+       struct ehci_hcd *ehci = container_of(nb, struct ehci_hcd,
+                                            cpufreq_transition);
+
+       switch (val) {
+       case CPUFREQ_PRECHANGE:
+               ehci_cpufreq_pause(ehci);
+               break;
+       case CPUFREQ_POSTCHANGE:
+               ehci_cpufreq_unpause(ehci);
+               break;
+       }
+       return 0;
+}
+
+#endif
+
+/*-------------------------------------------------------------------------*/
+
 static void ehci_watchdog (unsigned long param)
 {
        struct ehci_hcd         *ehci = (struct ehci_hcd *) param;
@@ -404,6 +456,10 @@ static void ehci_stop (struct usb_hcd *hcd)
        ehci_writel(ehci, 0, &ehci->regs->intr_enable);
        spin_unlock_irq(&ehci->lock);
 
+#ifdef CONFIG_CPU_FREQ
+       cpufreq_unregister_notifier(&ehci->cpufreq_transition,
+                                   CPUFREQ_TRANSITION_NOTIFIER);
+#endif
        /* let companion controllers work when we aren't */
        ehci_writel(ehci, 0, &ehci->regs->configured_flag);
 
@@ -509,6 +565,17 @@ static int ehci_init(struct usb_hcd *hcd)
        }
        ehci->command = temp;
 
+#ifdef CONFIG_CPU_FREQ
+       INIT_LIST_HEAD(&ehci->split_intr_qhs);
+       /*
+        * If the EHCI controller caches enough uframes, this probably
+        * isn't needed unless there are so many low/full speed devices
+        * that the controller's can't cache it all.
+        */
+       ehci->cpufreq_transition.notifier_call = ehci_cpufreq_notifier;
+       cpufreq_register_notifier(&ehci->cpufreq_transition,
+                                 CPUFREQ_TRANSITION_NOTIFIER);
+#endif
        return 0;
 }