Re: [PATCH v3 1/2] mtd: spi-nor: Make sure SFDP-based 4B_OPCODE support detection works correctly

[<Tudor.Ambarus@microchip.com>]

On 11/08/2018 07:08 PM, Boris Brezillon wrote:
> On Thu, 8 Nov 2018 16:55:29 +0000
> <Tudor.Ambarus@microchip.com> wrote:
> 
>> On 10/31/2018 04:45 PM, Boris Brezillon wrote:
>>> Some flash_info entries have the SPI_NOR_4B_OPCODES flag set to let the
>>> core know that the flash supports 4B opcode. While this solution works
>>> fine for id-based caps detection, it doesn't work that well when relying
>>> on SFDP-based caps detection. Let's add an SNOR_F_4B_OPCODES flag so that
>>> spi_nor_parse_bfpt() can add it when the BFPT_DWORD1_ADDRESS_BYTES
>>> field is set to BFPT_DWORD1_ADDRESS_BYTES_4_ONLY.
>>>
>>> Reported-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
>>> Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
>>> Tested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
>>> ---
>>> Changes in v3:
>>> - Clear SNOR_F_4B_OPCODES flag when SFDP fails
>>> - Add Alexandre R-b
>>>
>>> Changes in v2:
>>> - Fix the commit message
>>> - Fix the ->addr_width check
>>> - Add a comma at the end of the SNOR_F_4B_OPCODES definition
>>> ---
>>>  drivers/mtd/spi-nor/spi-nor.c | 12 +++++++++---
>>>  include/linux/mtd/spi-nor.h   |  1 +
>>>  2 files changed, 10 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>>> index 3e54e31889c7..798915b5c2b0 100644
>>> --- a/drivers/mtd/spi-nor/spi-nor.c
>>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>>> @@ -2643,6 +2643,7 @@ static int spi_nor_parse_bfpt(struct spi_nor *nor,
>>>  		break;
>>>  
>>>  	case BFPT_DWORD1_ADDRESS_BYTES_4_ONLY:
>>> +		nor->flags |= SNOR_F_4B_OPCODES;
>>>  		nor->addr_width = 4;
>>>  		break;
>>>  
>>> @@ -3252,6 +3253,7 @@ static int spi_nor_init_params(struct spi_nor *nor,
>>>  
>>>  		if (spi_nor_parse_sfdp(nor, &sfdp_params)) {
>>>  			nor->addr_width = 0;
>>> +			nor->flags &= ~SNOR_F_4B_OPCODES;
>>>  			/* restore previous erase map */
>>>  			memcpy(&nor->erase_map, &prev_map,
>>>  			       sizeof(nor->erase_map));
>>> @@ -3554,7 +3556,7 @@ static int spi_nor_init(struct spi_nor *nor)
>>>  
>>>  	if ((nor->addr_width == 4) &&
>>>  	    (JEDEC_MFR(nor->info) != SNOR_MFR_SPANSION) &&
>>> -	    !(nor->info->flags & SPI_NOR_4B_OPCODES)) {
>>> +	    !(nor->flags & SNOR_F_4B_OPCODES)) {
>>>  		/*
>>>  		 * If the RESET# pin isn't hooked up properly, or the system
>>>  		 * otherwise doesn't perform a reset command in the boot
>>> @@ -3588,7 +3590,7 @@ void spi_nor_restore(struct spi_nor *nor)
>>>  	/* restore the addressing mode */
>>>  	if ((nor->addr_width == 4) &&
>>>  	    (JEDEC_MFR(nor->info) != SNOR_MFR_SPANSION) &&
>>> -	    !(nor->info->flags & SPI_NOR_4B_OPCODES) &&
>>> +	    !(nor->flags & SNOR_F_4B_OPCODES) &&
>>>  	    (nor->flags & SNOR_F_BROKEN_RESET))
>>>  		set_4byte(nor, nor->info, 0);
>>>  }
>>> @@ -3746,11 +3748,15 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
>>>  		nor->addr_width = 4;
>>>  		if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
>>>  		    info->flags & SPI_NOR_4B_OPCODES)
>>> -			spi_nor_set_4byte_opcodes(nor, info);
>>> +			nor->flags |= SNOR_F_4B_OPCODES;
>>>  	} else {
>>>  		nor->addr_width = 3;
>>>  	}
>>>  
>>> +	if (nor->addr_width == 4 &&  
>>
>> Shouldn't SNOR_F_4B_OPCODES already imply nor->addr_width == 4?
> 
> Can't we have NORs supporting 4B opcodes but are less than 16MB? In
> this case SNOR_F_4B_OPCODES would be set and ->addr_width would be 3.

I guess not, it wouldn't make sense, but who knows ... :)

The 4-byte opcodes indicate that 4-bytes of address follow the instruction. And
4-byte addresses make sense for spi memories that exceed the 16MB density.

> 
>> When SNOR_F_4B_OPCODES comes from bfpt, addr_width is set to 4. For the id-based
>> caps detection, when mtd->size > 0x1000000, we set nor->addr_width = 4 too.
>>
>> The only uncovered case would be when
>>         } else if (info->addr_width) {
>>                 nor->addr_width = info->addr_width;
>>
>> but this can be solved by reordering the else if cases.
>>
>>         if (nor->addr_width) {
>>                 /* already configured from SFDP */
>>         } else if (mtd->size > 0x1000000) {
>> 		...
>>         } else if (info->addr_width) {
>>                 nor->addr_width = info->addr_width;
>>         } else {
>>                 nor->addr_width = 3;
>>         }
>>
>> What do you think?
> 
> I'd rather not change that in this patch, but feel free to propose
> a patch on top of mine to simplify the logic if you think it's
> needed.
> 

yeah, it can be made in a separate patch.

Cheers,
ta