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Message
From: Monisha Barooah<monisha.b@s...>
Date: Tue Sep 20 09:15:12 CEST 2005
Subject: [usb] Interrupt Registers for the OHCI controller
Hello All,
I had some doubts regarding the Interrupt registers of the OHCI controller.
There are three Interrupt Registers as mentioned in the OHCI specs - InterruptStatus, Interrupt Enable and Interrupt Disable registers.
The values of the Interrupt Enable and the Interrupt Disable registers should complement each other...but what we seem to observe here is that when we do the required settings of the bits sequentially in the Interrupt Disable and then the Interrupt Enable registers, the values of both the registers appear to be the same.
Like say we have provided, the values as:
HC_INTERRUPT_DISABLE - 0x4000003f and HC_INTERRUPT_ENABLE - 0x80000040, the values when read for both the registers, gives us 0x80000040.
Is there any issue with the sequencing of the values written to these registers? Meaning do we need to at first do the writes on the Interrupt Enable and then on the Interrupt Disable registers? or is the sequemce followed above okay?
Probably, due to the above settings, we are not seeing the corresponding bits of the Interrupt Status register getting set when we attach a device to the USB ports. We repeatedly are getting a value of 0 for that register in the ISR instead of the value corresponding to roothubstatus change.
Also, another things was that, Section 6.5 of the OHCI - 1.0 specs, says that for the interrupts to get trigerred, we require setting 'The MasterInterruptEnable bit in HcControl is set to '1'.' but there is no such bit in the HcControl register. Does this refer to the MIE bit of the Interrupt Enable register?
Thanking you for the help.
With Regards,
Monisha.
=====
Success is a journey, not a destination.
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