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apei_reg.c revision 1.1 
      1 /*	$NetBSD: apei_reg.c,v 1.1 2024/03/20 17:11:44 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 1.1 2024/03/20 17:11:44 riastradh Exp $");
     35 
     36 #include <sys/types.h>
     37 
     38 #include <dev/acpi/acpivar.h>
     39 #include <dev/acpi/apei_reg.h>
     40 
     41 /*
     42  * apei_read_register(Register, Mask, &X)
     43  *
     44  *	Read from Register, shifted out of position and then masked
     45  *	with Mask, and store the result in X.
     46  *
     47  *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#read-register
     48  *
     49  *	(I'm guessing this applies to both ERST and EINJ, even though
     50  *	that section is under the ERST part.)
     51  */
     52 ACPI_STATUS
     53 apei_read_register(ACPI_GENERIC_ADDRESS *Register, uint64_t Mask, uint64_t *p)
     54 {
     55 	const uint8_t BitOffset = Register->BitOffset;
     56 	uint64_t X;
     57 	ACPI_STATUS rv;
     58 
     59 	rv = AcpiRead(&X, Register);
     60 	if (ACPI_FAILURE(rv)) {
     61 		*p = 0;		/* XXX */
     62 		return rv;
     63 	}
     64 	X >>= BitOffset;
     65 	X &= Mask;
     66 
     67 	*p = X;
     68 	return AE_OK;
     69 }
     70 
     71 /*
     72  * apei_write_register(Register, Mask, preserve_register, X)
     73  *
     74  *	Write X, masked with Mask and shifted into position, to
     75  *	Register, preserving other bits if preserve_register is true.
     76  *
     77  *	https://uefi.org/specs/ACPI/6.5/18_Platform_Error_Interfaces.html#write-register
     78  *
     79  *	Note: The Preserve Register semantics is based on the clearer
     80  *	indentation at
     81  *	https://uefi.org/sites/default/files/resources/ACPI_5_1release.pdf#page=714
     82  *	which has been lost in more recent versions of the spec.
     83  */
     84 ACPI_STATUS
     85 apei_write_register(ACPI_GENERIC_ADDRESS *Register, uint64_t Mask,
     86     bool preserve_register, uint64_t X)
     87 {
     88 	const uint8_t BitOffset = Register->BitOffset;
     89 	ACPI_STATUS rv;
     90 
     91 	X &= Mask;
     92 	X <<= BitOffset;
     93 	if (preserve_register) {
     94 		uint64_t Y;
     95 
     96 		rv = AcpiRead(&Y, Register);
     97 		if (ACPI_FAILURE(rv))
     98 			return rv;
     99 		Y &= ~(Mask << BitOffset);
    100 		X |= Y;
    101 	}
    102 	return AcpiWrite(X, Register);
    103 }
    104