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diff --git a/Documentation/arm/Sharp-LH/VectoredInterruptController b/Documentation/arm/Sharp-LH/VectoredInterruptController deleted file mode 100644 index 23047e9..0000000 --- a/Documentation/arm/Sharp-LH/VectoredInterruptController +++ /dev/null @@ -1,80 +0,0 @@ -README on the Vectored Interrupt Controller of the LH7A404 -========================================================== - -The 404 revision of the LH7A40X series comes with two vectored -interrupts controllers. While the kernel does use some of the -features of these devices, it is far from the purpose for which they -were designed. - -When this README was written, the implementation of the VICs was in -flux. It is possible that some details, especially with priorities, -will change. - -The VIC support code is inspired by routines written by Sharp. - - -Priority Control ----------------- - -The significant reason for using the VIC's vectoring is to control -interrupt priorities. There are two tables in -arch/arm/mach-lh7a40x/irq-lh7a404.c that look something like this. - - static unsigned char irq_pri_vic1[] = { IRQ_GPIO3INTR, }; - static unsigned char irq_pri_vic2[] = { - IRQ_T3UI, IRQ_GPIO7INTR, - IRQ_UART1INTR, IRQ_UART2INTR, IRQ_UART3INTR, }; - -The initialization code reads these tables and inserts a vector -address and enable for each indicated IRQ. Vectored interrupts have -higher priority than non-vectored interrupts. So, on VIC1, -IRQ_GPIO3INTR will be served before any other non-FIQ interrupt. Due -to the way that the vectoring works, IRQ_T3UI is the next highest -priority followed by the other vectored interrupts on VIC2. After -that, the non-vectored interrupts are scanned in VIC1 then in VIC2. - - -ISR ---- - -The interrupt service routine macro get_irqnr() in -arch/arm/kernel/entry-armv.S scans the VICs for the next active -interrupt. The vectoring makes this code somewhat larger than it was -before using vectoring (refer to the LH7A400 implementation). In the -case where an interrupt is vectored, the implementation will tend to -be faster than the non-vectored version. However, the worst-case path -is longer. - -It is worth noting that at present, there is no need to read -VIC2_VECTADDR because the register appears to be shared between the -controllers. The code is written such that if this changes, it ought -to still work properly. - - -Vector Addresses ----------------- - -The proper use of the vectoring hardware would jump to the ISR -specified by the vectoring address. Linux isn't structured to take -advantage of this feature, though it might be possible to change -things to support it. - -In this implementation, the vectoring address is used to speed the -search for the active IRQ. The address is coded such that the lowest -6 bits store the IRQ number for vectored interrupts. These numbers -correspond to the bits in the interrupt status registers. IRQ zero is -the lowest interrupt bit in VIC1. IRQ 32 is the lowest interrupt bit -in VIC2. Because zero is a valid IRQ number and because we cannot -detect whether or not there is a valid vectoring address if that -address is zero, the eigth bit (0x100) is set for vectored interrupts. -The address for IRQ 0x18 (VIC2) is 0x118. Only the ninth bit is set -for the default handler on VIC1 and only the tenth bit is set for the -default handler on VIC2. - -In other words. - - 0x000 - no active interrupt - 0x1ii - vectored interrupt 0xii - 0x2xx - unvectored interrupt on VIC1 (xx is don't care) - 0x4xx - unvectored interrupt on VIC2 (xx is don't care) - |