Re: [RFC PATCH 03/23] scripts: add script to generate C header files from SVD XML files

[Peter Maydell]

On Mon, 5 Aug 2024 at 21:17, Octavian Purdila <tavip@google.com> wrote:
>
> From: Stefan Stanacar <stefanst@google.com>
>
> From: Stefan Stanacar <stefanst@google.com>
>
> The CMSIS System View Description format(CMSIS-SVD) is an XML based
> description of Arm Cortex-M microcontrollers provided and maintained
> by sillicon vendors. It includes details such as peripherals registers
> (down to bitfields), peripheral register block addresses, reset
> values, etc.
>
> This script uses this information to create header files that makes it
> easier to emulate peripherals.
>
> The script can be used to create either peripheral specific headers or
> board / system specific information. The script generated headers are
> similar to the SVDConv utility.
>
> Peripheral specific headers contains information such as register
> layout, register names and reset values for registers:
>
>   typedef struct {
>     ...
>     union {
>       uint32_t PSELID;              /* 0x00000FF8 Peripheral Select and
>                                      * Flexcomm module ID */
>       struct {
>         uint32_t PERSEL : 3;        /* [2..0] Peripheral Select */
>         uint32_t LOCK : 1;          /* [3..3] Lock the peripheral select */
>         uint32_t USARTPRESENT : 1;  /* [4..4] USART present indicator */
>         uint32_t SPIPRESENT : 1;    /* [5..5] SPI present indicator */
>         uint32_t I2CPRESENT : 1;    /* [6..6] I2C present indicator */
>         uint32_t I2SPRESENT : 1;    /* [7..7] I2S Present */
>         uint32_t : 4;
>         uint32_t ID : 20;           /* [31..12] Flexcomm ID */
>       } PSELID_b;
>     };

Bitfield layout in C isn't portable, so don't generate this kind
of union-of-a-integer-and-some-bitfields, please. You can
generate FIELD() macro invocations (see include/hw/registerfields.h)
which define shift/mask/length macros that can be used with
FIELD_EX*/FIELD_DP* to do extract/deposit operations.

>     ...
>   } FLEXCOMM_Type;                  /* Size = 4096 (0x1000) */
>
>   #define FLEXCOMM_PSELID_PERSEL_Pos (0UL)
>   #define FLEXCOMM_PSELID_PERSEL_Msk (0x7UL)
>   #define FLEXCOMM_PSELID_LOCK_Pos (3UL)
>   #define FLEXCOMM_PSELID_LOCK_Msk (0x8UL)
>   ...
>
>   typedef enum {                /* FLEXCOMM_PSELID_LOCK */
>     /* Peripheral select can be changed by software. */
>     FLEXCOMM_PSELID_LOCK_UNLOCKED = 0,
>     /* Peripheral select is locked and cannot be changed until this
>      * Flexcomm module or the entire device is reset. */
>     FLEXCOMM_PSELID_LOCK_LOCKED = 1,
>   } FLEXCOMM_PSELID_LOCK_Enum;
>   ...
>
>   #define FLEXCOMM_REGISTER_NAMES_ARRAY(_name) \
>     const char *_name[sizeof(FLEXCOMM_Type)] = { \
>         [4088 ... 4091] = "PSELID", \
>         [4092 ... 4095] = "PID", \
>     }
>
> Board specific headers contains information about peripheral base
> register addresses.

thanks
-- PMM