[Linuxarm] Re: [PATCH 1/2] mtd: spi-nor: check 4-byte address support when parsing 4bait

Hi Pratyush,

Thanks for the comments. Some replies below.

On 2021/1/29 19:16, Pratyush Yadav wrote:

Hi Yicong,

On 27/01/21 05:40PM, Yicong Yang wrote:

...

The spi-nor core will convert the address mode to 4-btye, without checking whether 4-byte address is supported or not. For example, the 16M s25fs128s1 can work under both 3-byte and 4-byte address and provides a 4bait table. The spi-nor will drive the flash under 4-byte address mode after parsing the 4bait and will cause it unusable on platforms doesn't support 4-byte.

Another problem caused by 4BAIT parser prematurely selecting the address width. See [0].

Let's fix this 4BAIT problem once and for all. Instead of setting nor->addr_width to 4 in spi_nor_parse_4bait(), just set SNOR_F_HAS_4BAIT (which is already being done). Then in spi_nor_default_setup(), use this information when negotiating the read/write/program commands with the controller to determine the correct address width to use.

The idea is great. ideally we should check the buswidth and commands in spi_nor_default_setup() and finally set address width in spi_nor_set_addr_width().

This refactor is easier said than done. We don't associate address width information with a command. Just protocol, opcode, and dummy cycles (only for read commands). A new mechanism needs to be added where we associate a set of supported addresses with a command and then the command negotiation can use all this information to arrive at the optimal set of commands.

With this in mind, it would be great if you can come up with a patch to add such a mechanism. But I would also be OK with this fix with the condition that it is clearly marked as a temporary fix, and mentions what should ideally be done.

i'd like to get this issue fixed first to make the flash work properly, if possible. then to do the refactor as it may take me sometime.

...

Add checking of 4-byte address support when parsing the 4bait table, stop converting the address mode if it's not supported.

Signed-off-by: Yicong Yang yangyicong@hisilicon.com

drivers/mtd/spi-nor/sfdp.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+)

diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c index 6ee7719..fdafc9b 100644 --- a/drivers/mtd/spi-nor/sfdp.c +++ b/drivers/mtd/spi-nor/sfdp.c @@ -940,6 +940,27 @@ static int spi_nor_parse_smpt(struct spi_nor *nor, return ret; }

+static int spi_nor_spimem_check_4byte_addr(struct spi_nor *nor,

• 			   const struct spi_nor_read_command *read)
  

+{

• struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(read->opcode, 1),

• 			  SPI_MEM_OP_ADDR(4, 0, 1),
  

• 			  SPI_MEM_OP_DUMMY(0, 1),
  

• 			  SPI_MEM_OP_DATA_IN(0, NULL, 1));
  

Set buswidths to 0 here...

ok.

...

• op.cmd.buswidth = spi_nor_get_protocol_inst_nbits(read->proto);
• op.addr.buswidth = spi_nor_get_protocol_addr_nbits(read->proto);
• op.data.buswidth = spi_nor_get_protocol_data_nbits(read->proto);
• op.dummy.buswidth = op.addr.buswidth;

... and use spi_nor_spimem_setup_op() to do this. It will also take care of setting up DTR ops.

will change to the new function, i didn't notice it. :)

Thanks, Yicong

...

• op.dummy.nbytes = (read->num_mode_clocks + read->num_wait_states) *

• 	  op.dummy.buswidth / 8;
  

• if (!spi_mem_supports_op(nor->spimem, &op))

• return -EOPNOTSUPP;
  

• return 0;

+}

/**

• spi_nor_parse_4bait() - parse the 4-Byte Address Instruction Table
• @nor: pointer to a 'struct spi_nor'.

@@ -1061,6 +1082,33 @@ static int spi_nor_parse_4bait(struct spi_nor *nor, goto out;

/*

• * Check whether the 4-byte address is supported before converting
  

• * the instruction set to 4-byte.
  

• */
  

• if (nor->spimem) {

• bool support = false;
  

• for (i = 0; i < SNOR_CMD_READ_MAX; i++) {
  

• 	struct spi_nor_read_command read_cmd;
  

• 	memcpy(&read_cmd, &params->reads[i], sizeof(read_cmd));
  

• 	read_cmd.opcode = spi_nor_convert_3to4_read(read_cmd.opcode);
  

• 	if (!spi_nor_spimem_check_4byte_addr(nor, &read_cmd)) {
  

• 		support = true;
  

• 		break;
  

• 	}
  

• }
  

• /*
  

•  * No supported 4-byte instruction is found, stop parsing the
  

•  * 4bait table.
  

•  */
  

• if (!support)
  

• 	goto out;
  

• }
• /*
  • Discard all operations from the 4-byte instruction set which are
  • not supported by this memory.
  */

[0] https://lore.kernel.org/linux-mtd/20201212115817.5122-1-vigneshr@ti.com/