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Submission + - Full DMA access for USB-OTG on PPC405EX (huntercobbs.com)

hcob$ writes: "I'm doing some early prototying of a AMCC PPC405EX based board. Here's just a few of my actions so far to let you know how much frustration this one little problem has casued me:

        * Fixed the broken OpenWRT support for the AMCC Kilauea Dev Board with patches, backports and Makefile Modification
        * Ported DENX deployed USB-OTG support with the dwc_otg driver
        * Reworked the flash map so that there is a custom fall-back ramdisk and a fully-permenant rootfs

Then comes the next problem. After finally porting in the dwc_otg USB driver to the OpenWRT patched kernel, I went about hooking up some usb-serial devices that we planned to use. They detected properly and registered. The I open up a minicom connection and WAM! 99-100% IRQ usage. Completely bogged down the system. Turns out, the device is running in an IRQ(Slave) mode and triggering interrupts that need to be serviced at an insane rate (had a back log of 89k interrupts at some points). After two weeks of focusing on this problem, I finally noticed something odd in my kernel build."

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