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sys/bit: provide CPU_HAS_SRAM_BITBAND

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CPU_HAS_SRAM_BITBAND can be used to check whether bit-banding is supported for
all of SRAM. With partially supported bit-banding, this feature is more of a
foot gun that a valuable tool.

(cherry picked from commit 51db33375a1c3fc250ab53762829f1226d22c5bc)
This commit is contained in:
Marian Buschsieweke 2021-01-20 09:16:51 +01:00
parent 320a431fda
commit a8b6c0579c
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GPG Key ID: 61F64C6599B1539F
2 changed files with 24 additions and 2 deletions
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4
cpu/kinetis/include/cpu_conf.h
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@ -49,7 +49,9 @@ extern "C"
* @{
*/
#ifdef BITBAND_REG32
#define CPU_HAS_BITBAND 1
#define CPU_HAS_BITBAND 1
/* SRAM_L is mapped before the bit-banding region, only SRAM_U can be used for bit-banding */
#define CPU_HAS_SRAM_BITBAND 0
#endif
/** @} */

22
sys/include/bit.h
View File

@ -31,11 +31,31 @@ extern "C" {
#if !BITBAND_FUNCTIONS_PROVIDED
#if DOXYGEN
/** @brief Flag for telling if the CPU has hardware bit band support */
/**
* @brief Flag to check if the CPU has hardware bit band support
*/
#define CPU_HAS_BITBAND 1 || 0 (1 if CPU implements bit-banding, 0 if not)
/**
* @brief Flag to check if bit-banding is supported for all of SRAM
*
* @details Bit-banding in SRAM is only supported (if available at all) for a
* 1 MiB region in the address space. If not all of SRAM is mapped
* there, it is safest to not use bit-banding at all. Luckily, only
* few vendors decided to implement partially broken bit-banding.
*
* @retval 1 All of SRAM is bit-banding capable
* @retval 0 (At least one part) SRAM is not bit-banding capable
*/
#define CPU_HAS_SRAM_BITBAND 1 || 0
#endif
#if CPU_HAS_BITBAND || DOXYGEN
/* Most CPUs with bitband have all of SRAM mapped in the bit-banding region.
* The few oddballs have to define it to zero in cpu_conf.h */
#ifndef CPU_HAS_SRAM_BITBAND
#define CPU_HAS_SRAM_BITBAND 1
#endif
/* Some MCUs provide a bitband address space for atomically accessing
* single bits of peripheral registers, and sometimes for RAM as well */
/**