a1eb1cdf4e
The algorithm used in baboon_irq() appears to be subject to a race condition: an IRQ flag could be lost if asserted between the MOV instructions from and to the interrupt flag register. However, testing shows that the write to the flag register has no effect. Rewrite this loop to remove the apparent race condition. No-one seems to know how to clear Baboon IRQ flags, or whether that's even possible, so add a comment about this. Tested-by: Stan Johnson <userm57@yahoo.com> Signed-off-by: Finn Thain <fthain@telegraphics.com.au> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
89 lines
1.8 KiB
C
89 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Baboon Custom IC Management
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*
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* The Baboon custom IC controls the IDE, PCMCIA and media bay on the
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* PowerBook 190. It multiplexes multiple interrupt sources onto the
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* Nubus slot $C interrupt.
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/irq.h>
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#include <asm/macintosh.h>
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#include <asm/macints.h>
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#include <asm/mac_baboon.h>
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int baboon_present;
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static volatile struct baboon *baboon;
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/*
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* Baboon initialization.
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*/
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void __init baboon_init(void)
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{
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if (macintosh_config->ident != MAC_MODEL_PB190) {
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baboon = NULL;
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baboon_present = 0;
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return;
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}
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baboon = (struct baboon *) BABOON_BASE;
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baboon_present = 1;
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pr_debug("Baboon detected at %p\n", baboon);
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}
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/*
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* Baboon interrupt handler.
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* XXX how do you clear a pending IRQ? is it even necessary?
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*/
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static void baboon_irq(struct irq_desc *desc)
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{
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short events, irq_bit;
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int irq_num;
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events = baboon->mb_ifr & 0x07;
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irq_num = IRQ_BABOON_0;
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irq_bit = 1;
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do {
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if (events & irq_bit) {
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events &= ~irq_bit;
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generic_handle_irq(irq_num);
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}
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++irq_num;
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irq_bit <<= 1;
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} while (events);
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}
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/*
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* Register the Baboon interrupt dispatcher on nubus slot $C.
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*/
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void __init baboon_register_interrupts(void)
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{
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irq_set_chained_handler(IRQ_NUBUS_C, baboon_irq);
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}
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/*
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* The means for masking individual Baboon interrupts remains a mystery.
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* However, since we only use the IDE IRQ, we can just enable/disable all
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* Baboon interrupts. If/when we handle more than one Baboon IRQ, we must
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* either figure out how to mask them individually or else implement the
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* same workaround that's used for NuBus slots (see nubus_disabled and
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* via_nubus_irq_shutdown).
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*/
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void baboon_irq_enable(int irq)
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{
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mac_irq_enable(irq_get_irq_data(IRQ_NUBUS_C));
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}
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void baboon_irq_disable(int irq)
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{
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mac_irq_disable(irq_get_irq_data(IRQ_NUBUS_C));
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}
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