From 60949b7b805424f21326b450ca4f1806c06d982e Mon Sep 17 00:00:00 2001 From: Clément Léger Date: Mon, 26 Aug 2024 12:16:44 +0200 Subject: ACPI: CPPC: Fix MASK_VAL() usage MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MASK_VAL() was added as a way to handle bit_offset and bit_width for registers located in system memory address space. However, while suited for reading, it does not work for writing and result in corrupted registers when writing values with bit_offset > 0. Moreover, when a register is collocated with another one at the same address but with a different mask, the current code results in the other registers being overwritten with 0s. The write procedure for SYSTEM_MEMORY registers should actually read the value, mask it, update it and write it with the updated value. Moreover, since registers can be located in the same word, we must take care of locking the access before doing it. We should potentially use a global lock since we don't know in if register addresses aren't shared with another _CPC package but better not encourage vendors to do so. Assume that registers can use the same word inside a _CPC package and thus, use a per _CPC package lock. Fixes: 2f4a4d63a193 ("ACPI: CPPC: Use access_width over bit_width for system memory accesses") Signed-off-by: Clément Léger Link: https://patch.msgid.link/20240826101648.95654-1-cleger@rivosinc.com [ rjw: Dropped redundant semicolon ] Signed-off-by: Rafael J. Wysocki --- include/acpi/cppc_acpi.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/acpi') diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h index 930b6afba6f4..e1720d930666 100644 --- a/include/acpi/cppc_acpi.h +++ b/include/acpi/cppc_acpi.h @@ -64,6 +64,8 @@ struct cpc_desc { int cpu_id; int write_cmd_status; int write_cmd_id; + /* Lock used for RMW operations in cpc_write() */ + spinlock_t rmw_lock; struct cpc_register_resource cpc_regs[MAX_CPC_REG_ENT]; struct acpi_psd_package domain_info; struct kobject kobj; -- cgit v1.2.3