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apei_reg.c revision 1.2 
      1 /*	$NetBSD: apei_reg.c,v 1.2 2024/03/22 20:48:05 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 1.2 2024/03/22 20:48:05 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 store the result in X.
     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 ACPI_STATUS
     54 apei_read_register(ACPI_GENERIC_ADDRESS *Register, struct apei_mapreg *map,
     55     uint64_t Mask, uint64_t *p)
     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 	*p = X;
     65 	return AE_OK;
     66 }
     67 
     68 /*
     69  * apei_write_register(Register, map, Mask, preserve_register, X)
     70  *
     71  *	Write X, masked with Mask and shifted into position, to
     72  *	Register, mapped at map, preserving other bits if
     73  *	preserve_register is true.
     74  *
     75  *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#write-register
     76  *
     77  *	Note: The Preserve Register semantics is based on the clearer
     78  *	indentation at
     79  *	https://uefi.org/sites/default/files/resources/ACPI_5_1release.pdf#page=714
     80  *	which has been lost in more recent versions of the spec.
     81  */
     82 ACPI_STATUS
     83 apei_write_register(ACPI_GENERIC_ADDRESS *Register, struct apei_mapreg *map,
     84     uint64_t Mask, bool preserve_register, uint64_t X)
     85 {
     86 	const uint8_t BitOffset = Register->BitOffset;
     87 
     88 	X &= Mask;
     89 	X <<= BitOffset;
     90 	if (preserve_register) {
     91 		uint64_t Y;
     92 
     93 		Y = apei_mapreg_read(Register, map);
     94 		Y &= ~(Mask << BitOffset);
     95 		X |= Y;
     96 	}
     97 	apei_mapreg_write(Register, map, X);
     98 	return AE_OK;
     99 }
    100