Re: [PATCH v5 2/6] mtd: m25p80: add support of SPI 1-2-2 and 1-4-4 protocols

[Marek Vasut <marek.vasut@gmail.com>]

On 03/23/2017 12:33 AM, Cyrille Pitchen wrote:
> Before this patch, m25p80_read() supported few SPI protocols:
> - regular SPI 1-1-1
> - SPI Dual Output 1-1-2
> - SPI Quad Output 1-1-4
> On the other hand, m25p80_write() only supported SPI 1-1-1.
> 
> This patch updates both m25p80_read() and m25p80_write() functions to let
> them support SPI 1-2-2 and SPI 1-4-4 protocols for Fast Read and Page
> Program SPI commands.
> 
> It adopts a conservative approach to avoid regressions. Hence the new
                                             ^ FYI, regression != bug

> implementations try to be as close as possible to the old implementations,
> so the main differences are:
> - the tx_nbits values now being set properly for the spi_transfer
>   structures carrying the (op code + address/dummy) bytes
> - and the spi_transfer structure being split into 2 spi_transfer
>   structures when the numbers of I/O lines are different for op code and
>   for address/dummy byte transfers on the SPI bus.
> 
> Besides, the current spi-nor framework supports neither the SPI 2-2-2 nor
> the SPI 4-4-4 protocols. So, for now, we don't need to update the
> m25p80_{read|write}_reg() functions as SPI 1-1-1 is the only one possible
> protocol.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen@atmel.com>
> ---
>  drivers/mtd/devices/m25p80.c | 120 ++++++++++++++++++++++++++++++++-----------
>  1 file changed, 90 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> index 68986a26c8fe..64d562efc25d 100644
> --- a/drivers/mtd/devices/m25p80.c
> +++ b/drivers/mtd/devices/m25p80.c
> @@ -34,6 +34,19 @@ struct m25p {
>  	u8			command[MAX_CMD_SIZE];
>  };
>  
> +static inline void m25p80_proto2nbits(enum spi_nor_protocol proto,
> +				      unsigned int *inst_nbits,
> +				      unsigned int *addr_nbits,
> +				      unsigned int *data_nbits)
> +{

Why don't we just have some generic macros to extract the number of bits
from $proto ?

> +	if (inst_nbits)
> +		*inst_nbits = spi_nor_get_protocol_inst_width(proto);
> +	if (addr_nbits)
> +		*addr_nbits = spi_nor_get_protocol_addr_width(proto);
> +	if (data_nbits)
> +		*data_nbits = spi_nor_get_protocol_data_width(proto);
> +}
> +
>  static int m25p80_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
>  {
>  	struct m25p *flash = nor->priv;
> @@ -78,11 +91,16 @@ static ssize_t m25p80_write(struct spi_nor *nor, loff_t to, size_t len,
>  {
>  	struct m25p *flash = nor->priv;
>  	struct spi_device *spi = flash->spi;
> -	struct spi_transfer t[2] = {};
> +	unsigned int inst_nbits, addr_nbits, data_nbits, data_idx;
> +	struct spi_transfer t[3] = {};
>  	struct spi_message m;
>  	int cmd_sz = m25p_cmdsz(nor);
>  	ssize_t ret;
>  
> +	/* get transfer protocols. */
> +	m25p80_proto2nbits(nor->write_proto, &inst_nbits,
> +			   &addr_nbits, &data_nbits);
> +
>  	spi_message_init(&m);
>  
>  	if (nor->program_opcode == SPINOR_OP_AAI_WP && nor->sst_write_second)
> @@ -92,12 +110,27 @@ static ssize_t m25p80_write(struct spi_nor *nor, loff_t to, size_t len,
>  	m25p_addr2cmd(nor, to, flash->command);
>  
>  	t[0].tx_buf = flash->command;
> +	t[0].tx_nbits = inst_nbits;
>  	t[0].len = cmd_sz;
>  	spi_message_add_tail(&t[0], &m);
>  
> -	t[1].tx_buf = buf;
> -	t[1].len = len;
> -	spi_message_add_tail(&t[1], &m);
> +	/* split the op code and address bytes into two transfers if needed. */
> +	data_idx = 1;
> +	if (addr_nbits != inst_nbits) {
> +		t[0].len = 1;
> +
> +		t[1].tx_buf = &flash->command[1];
> +		t[1].tx_nbits = addr_nbits;
> +		t[1].len = cmd_sz - 1;
> +		spi_message_add_tail(&t[1], &m);
> +
> +		data_idx = 2;
> +	}
> +
> +	t[data_idx].tx_buf = buf;
> +	t[data_idx].tx_nbits = data_nbits;
> +	t[data_idx].len = len;
> +	spi_message_add_tail(&t[data_idx], &m);
>  
>  	ret = spi_sync(spi, &m);
>  	if (ret)
> @@ -109,18 +142,6 @@ static ssize_t m25p80_write(struct spi_nor *nor, loff_t to, size_t len,
>  	return ret;
>  }
>  
> -static inline unsigned int m25p80_rx_nbits(struct spi_nor *nor)
> -{
> -	switch (nor->read_proto) {
> -	case SNOR_PROTO_1_1_2:
> -		return 2;
> -	case SNOR_PROTO_1_1_4:
> -		return 4;
> -	default:
> -		return 0;
> -	}
> -}
> -
>  /*
>   * Read an address range from the nor chip.  The address range
>   * may be any size provided it is within the physical boundaries.
> @@ -130,13 +151,19 @@ static ssize_t m25p80_read(struct spi_nor *nor, loff_t from, size_t len,
>  {
>  	struct m25p *flash = nor->priv;
>  	struct spi_device *spi = flash->spi;
> -	struct spi_transfer t[2];
> +	unsigned int inst_nbits, addr_nbits, data_nbits, data_idx;
> +	struct spi_transfer t[3];
>  	struct spi_message m;
>  	unsigned int dummy = nor->read_dummy;
>  	ssize_t ret;
> +	int cmd_sz;
> +
> +	/* get transfer protocols. */
> +	m25p80_proto2nbits(nor->read_proto, &inst_nbits,
> +			   &addr_nbits, &data_nbits);
>  
>  	/* convert the dummy cycles to the number of bytes */
> -	dummy /= 8;
> +	dummy = (dummy * addr_nbits) / 8;
>  
>  	if (spi_flash_read_supported(spi)) {
>  		struct spi_flash_read_message msg;
> @@ -149,10 +176,9 @@ static ssize_t m25p80_read(struct spi_nor *nor, loff_t from, size_t len,
>  		msg.read_opcode = nor->read_opcode;
>  		msg.addr_width = nor->addr_width;
>  		msg.dummy_bytes = dummy;
> -		/* TODO: Support other combinations */
> -		msg.opcode_nbits = SPI_NBITS_SINGLE;
> -		msg.addr_nbits = SPI_NBITS_SINGLE;
> -		msg.data_nbits = m25p80_rx_nbits(nor);
> +		msg.opcode_nbits = inst_nbits;
> +		msg.addr_nbits = addr_nbits;
> +		msg.data_nbits = data_nbits;
>  
>  		ret = spi_flash_read(spi, &msg);
>  		if (ret < 0)
> @@ -167,20 +193,45 @@ static ssize_t m25p80_read(struct spi_nor *nor, loff_t from, size_t len,
>  	m25p_addr2cmd(nor, from, flash->command);
>  
>  	t[0].tx_buf = flash->command;
> +	t[0].tx_nbits = inst_nbits;
>  	t[0].len = m25p_cmdsz(nor) + dummy;
>  	spi_message_add_tail(&t[0], &m);
>  
> -	t[1].rx_buf = buf;
> -	t[1].rx_nbits = m25p80_rx_nbits(nor);
> -	t[1].len = min3(len, spi_max_transfer_size(spi),
> -			spi_max_message_size(spi) - t[0].len);
> -	spi_message_add_tail(&t[1], &m);
> +	/*
> +	 * Set all dummy/mode cycle bits to avoid sending some manufacturer
> +	 * specific pattern, which might make the memory enter its Continuous
> +	 * Read mode by mistake.
> +	 * Based on the different mode cycle bit patterns listed and described
> +	 * in the JESD216B speficication, the 0xff value works for all memories
                           ^
                           specification, typo

> +	 * and all manufacturers.
> +	 */
> +	cmd_sz = t[0].len;
> +	memset(flash->command + cmd_sz - dummy, 0xff, dummy);
> +
> +	/* split the op code and address bytes into two transfers if needed. */
> +	data_idx = 1;
> +	if (addr_nbits != inst_nbits) {
> +		t[0].len = 1;
> +
> +		t[1].tx_buf = &flash->command[1];
> +		t[1].tx_nbits = addr_nbits;
> +		t[1].len = cmd_sz - 1;
> +		spi_message_add_tail(&t[1], &m);
> +
> +		data_idx = 2;
> +	}
> +
> +	t[data_idx].rx_buf = buf;
> +	t[data_idx].rx_nbits = data_nbits;
> +	t[data_idx].len = min3(len, spi_max_transfer_size(spi),
> +			       spi_max_message_size(spi) - cmd_sz);
> +	spi_message_add_tail(&t[data_idx], &m);
>  
>  	ret = spi_sync(spi, &m);
>  	if (ret)
>  		return ret;
>  
> -	ret = m.actual_length - m25p_cmdsz(nor) - dummy;
> +	ret = m.actual_length - cmd_sz;
>  	if (ret < 0)
>  		return -EIO;
>  	return ret;
> @@ -223,11 +274,20 @@ static int m25p_probe(struct spi_device *spi)
>  	spi_set_drvdata(spi, flash);
>  	flash->spi = spi;
>  
> -	if (spi->mode & SPI_RX_QUAD)
> +	if (spi->mode & SPI_RX_QUAD) {
>  		hwcaps.mask |= SNOR_HWCAPS_READ_1_1_4;
> -	else if (spi->mode & SPI_RX_DUAL)
> +
> +		if (spi->mode & SPI_TX_QUAD)
> +			hwcaps.mask |= (SNOR_HWCAPS_READ_1_4_4 |
> +					SNOR_HWCAPS_PP_1_1_4 |
> +					SNOR_HWCAPS_PP_1_4_4);
> +	} else if (spi->mode & SPI_RX_DUAL) {
>  		hwcaps.mask |= SNOR_HWCAPS_READ_1_1_2;
>  
> +		if (spi->mode & SPI_TX_DUAL)
> +			hwcaps.mask |= SNOR_HWCAPS_READ_1_2_2;
> +	}
> +
>  	if (data && data->name)
>  		nor->mtd.name = data->name;
>  
> 


-- 
Best regards,
Marek Vasut