diff options
| -rw-r--r-- | src/flash/nor/spearsmi.c | 26 |
1 files changed, 22 insertions, 4 deletions
diff --git a/src/flash/nor/spearsmi.c b/src/flash/nor/spearsmi.c index 19a44054..4902a446 100644 --- a/src/flash/nor/spearsmi.c +++ b/src/flash/nor/spearsmi.c @@ -17,6 +17,16 @@ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * ***************************************************************************/ +/* SPEAr Serial Memory Interface (SMI) controller is a SPI bus controller + * specifically designed for SPI memories. + * Only SPI "mode 3" (CPOL=1 and CPHA=1) is supported. + * Two working modes are available: + * - SW mode: the SPI is controlled by SW. Any custom commands can be sent + * on the bus. + * - HW mode: the SPI but is under SMI control. Memory content is directly + * accessible in CPU memory space. CPU can read, write and execute memory + * content. */ + /* ATTENTION: * To have flash memory mapped in CPU memory space, the SMI controller * have to be in "HW mode". This requires following constraints: @@ -136,6 +146,9 @@ struct flash_device { .size_in_bytes = size \ } +/* List below is taken from Linux driver. It is not exhaustive of all the + * possible SPI memories, nor exclusive for SMI. Could be shared with + * other SPI drivers. */ static struct flash_device flash_devices[] = { /* name, erase_cmd, device_id, pagesize, sectorsize, size_in_bytes */ FLASH_ID("st m25p05", 0xd8, 0x00102020, 0x80, 0x8000, 0x10000), @@ -217,6 +230,9 @@ static int poll_tff(struct target *target, uint32_t io_base, int timeout) return ERROR_FLASH_OPERATION_FAILED; } +/* Read the status register of the external SPI flash chip. + * The operation is triggered by setting SMI_RSR bit. + * SMI sends the proper SPI command (0x05) and returns value in SMI_SR */ static int read_status_reg(struct flash_bank *bank, uint32_t *status) { struct target *target = bank->target; @@ -235,7 +251,6 @@ static int read_status_reg(struct flash_bank *bank, uint32_t *status) /* clear transmit finished flag */ SMI_CLEAR_TFF(); - /* Check write enabled */ *status = SMI_READ_REG(SMI_SR) & 0x0000ffff; /* clean-up SMI_CR2 */ @@ -268,6 +283,9 @@ static int wait_till_ready(struct flash_bank *bank, int timeout) return ERROR_FAIL; } +/* Send "write enable" command to SPI flash chip. + * The operation is triggered by setting SMI_WE bit, and SMI sends + * the proper SPI command (0x06) */ static int smi_write_enable(struct flash_bank *bank) { struct target *target = bank->target; @@ -337,7 +355,7 @@ static int smi_erase_sector(struct flash_bank *bank, int sector) /* clear transmit finished flag */ SMI_CLEAR_TFF(); - /* send erase command */ + /* send SPI command "block erase" */ cmd = erase_command(spearsmi_info, bank->sectors[sector].offset); SMI_WRITE_REG(SMI_TR, cmd); SMI_WRITE_REG(SMI_CR2, spearsmi_info->bank_num | SMI_SEND | SMI_TX_LEN_4); @@ -554,7 +572,7 @@ static int read_flash_id(struct flash_bank *bank, uint32_t *id) /* clear transmit finished flag */ SMI_CLEAR_TFF(); - /* Require read flash ID */ + /* Send SPI command "read ID" */ SMI_WRITE_REG(SMI_TR, SMI_READ_ID); SMI_WRITE_REG(SMI_CR2, spearsmi_info->bank_num | SMI_SEND | SMI_RX_LEN_3 | SMI_TX_LEN_1); @@ -565,7 +583,7 @@ static int read_flash_id(struct flash_bank *bank, uint32_t *id) /* clear transmit finished flag */ SMI_CLEAR_TFF(); - /* read ID */ + /* read ID from Receive Register */ *id = SMI_READ_REG(SMI_RR) & 0x00ffffff; return ERROR_OK; } |