From ace9429bb58fd418f0c81d4c2835699bddf6bde6 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:27:49 +0200 Subject: Adding upstream version 6.6.15. Signed-off-by: Daniel Baumann --- arch/m68k/mm/hwtest.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 arch/m68k/mm/hwtest.c (limited to 'arch/m68k/mm/hwtest.c') diff --git a/arch/m68k/mm/hwtest.c b/arch/m68k/mm/hwtest.c new file mode 100644 index 0000000000..fe99aa9998 --- /dev/null +++ b/arch/m68k/mm/hwtest.c @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Tests for presence or absence of hardware registers. + * This code was originally in atari/config.c, but I noticed + * that it was also in drivers/nubus/nubus.c and I wanted to + * use it in hp300/config.c, so it seemed sensible to pull it + * out into its own file. + * + * The test is for use when trying to read a hardware register + * that isn't present would cause a bus error. We set up a + * temporary handler so that this doesn't kill the kernel. + * + * There is a test-by-reading and a test-by-writing; I present + * them here complete with the comments from the original atari + * config.c... + * -- PMM , 05/1998 + */ + +/* This function tests for the presence of an address, specially a + * hardware register address. It is called very early in the kernel + * initialization process, when the VBR register isn't set up yet. On + * an Atari, it still points to address 0, which is unmapped. So a bus + * error would cause another bus error while fetching the exception + * vector, and the CPU would do nothing at all. So we needed to set up + * a temporary VBR and a vector table for the duration of the test. + */ + +#include + +int hwreg_present(volatile void *regp) +{ + int ret = 0; + unsigned long flags; + long save_sp, save_vbr; + long tmp_vectors[3]; + + local_irq_save(flags); + __asm__ __volatile__ ( + "movec %/vbr,%2\n\t" + "movel #Lberr1,%4@(8)\n\t" + "movec %4,%/vbr\n\t" + "movel %/sp,%1\n\t" + "moveq #0,%0\n\t" + "tstb %3@\n\t" + "nop\n\t" + "moveq #1,%0\n" + "Lberr1:\n\t" + "movel %1,%/sp\n\t" + "movec %2,%/vbr" + : "=&d" (ret), "=&r" (save_sp), "=&r" (save_vbr) + : "a" (regp), "a" (tmp_vectors) + ); + local_irq_restore(flags); + + return ret; +} +EXPORT_SYMBOL(hwreg_present); + +/* Basically the same, but writes a value into a word register, protected + * by a bus error handler. Returns 1 if successful, 0 otherwise. + */ + +int hwreg_write(volatile void *regp, unsigned short val) +{ + int ret; + unsigned long flags; + long save_sp, save_vbr; + long tmp_vectors[3]; + + local_irq_save(flags); + __asm__ __volatile__ ( + "movec %/vbr,%2\n\t" + "movel #Lberr2,%4@(8)\n\t" + "movec %4,%/vbr\n\t" + "movel %/sp,%1\n\t" + "moveq #0,%0\n\t" + "movew %5,%3@\n\t" + "nop\n\t" + /* + * If this nop isn't present, 'ret' may already be loaded + * with 1 at the time the bus error happens! + */ + "moveq #1,%0\n" + "Lberr2:\n\t" + "movel %1,%/sp\n\t" + "movec %2,%/vbr" + : "=&d" (ret), "=&r" (save_sp), "=&r" (save_vbr) + : "a" (regp), "a" (tmp_vectors), "g" (val) + ); + local_irq_restore(flags); + + return ret; +} +EXPORT_SYMBOL(hwreg_write); + -- cgit v1.2.3