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      1 /*	$NetBSD: apei_reg.c,v 1.3 2024/03/22 20:48:14 riastradh Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2024 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 /*
     30  * APEI register access for ERST/EINJ action instructions
     31  */
     32 
     33 #include <sys/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: apei_reg.c,v 1.3 2024/03/22 20:48:14 riastradh Exp $");
     35 
     36 #include <sys/types.h>
     37 
     38 #include <dev/acpi/acpivar.h>
     39 #include <dev/acpi/apei_mapreg.h>
     40 #include <dev/acpi/apei_reg.h>
     41 
     42 /*
     43  * apei_read_register(Register, map, Mask, &X)
     44  *
     45  *	Read from Register mapped at map, shifted out of position and
     46  *	then masked with Mask, and return the result.
     47  *
     48  *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#read-register
     49  *
     50  *	(I'm guessing this applies to both ERST and EINJ, even though
     51  *	that section is under the ERST part.)
     52  */
     53 uint64_t
     54 apei_read_register(ACPI_GENERIC_ADDRESS *Register, struct apei_mapreg *map,
     55     uint64_t Mask)
     56 {
     57 	const uint8_t BitOffset = Register->BitOffset;
     58 	uint64_t X;
     59 
     60 	X = apei_mapreg_read(Register, map);
     61 	X >>= BitOffset;
     62 	X &= Mask;
     63 
     64 	return X;
     65 }
     66 
     67 /*
     68  * apei_write_register(Register, map, Mask, preserve_register, X)
     69  *
     70  *	Write X, masked with Mask and shifted into position, to
     71  *	Register, mapped at map, preserving other bits if
     72  *	preserve_register is true.
     73  *
     74  *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#write-register
     75  *
     76  *	Note: The Preserve Register semantics is based on the clearer
     77  *	indentation at
     78  *	https://uefi.org/sites/default/files/resources/ACPI_5_1release.pdf#page=714
     79  *	which has been lost in more recent versions of the spec.
     80  */
     81 void
     82 apei_write_register(ACPI_GENERIC_ADDRESS *Register, struct apei_mapreg *map,
     83     uint64_t Mask, bool preserve_register, uint64_t X)
     84 {
     85 	const uint8_t BitOffset = Register->BitOffset;
     86 
     87 	X &= Mask;
     88 	X <<= BitOffset;
     89 	if (preserve_register) {
     90 		uint64_t Y;
     91 
     92 		Y = apei_mapreg_read(Register, map);
     93 		Y &= ~(Mask << BitOffset);
     94 		X |= Y;
     95 	}
     96 	apei_mapreg_write(Register, map, X);
     97 }
     98