Re: [PATCH 1/2] mtd: spi-nor: add an option to force 3byte adressing mode

From: Marcin Wojtas
Date: Mon Aug 28 2017 - 17:54:12 EST


Hi Geert,

>> +- spi-3byte-addressing - Empty property indicating device access to be done
>> + only in 3byte addressing mode.
>
> spi-force-3byte-addressing?

I can change it, no problem. I thought of this, but was affraid if the
property wouldn't be too long.

>
>> Some SPI controllers and devices support Dual and Quad SPI transfer mode.
>> It allows data in the SPI system to be transferred using 2 wires (DUAL) or 4
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index 1413828..029c87d 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -2002,7 +2002,17 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
>> if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
>> info->flags & SPI_NOR_4B_OPCODES)
>> spi_nor_set_4byte_opcodes(nor, info);
>> - else
>> + else if (of_property_read_bool(np, "spi-3byte-addressing")) {
>> + /*
>> + * Do not enter 4byte mode in order to prevent
>> + * the early bootloader to come up on non-default
>> + * SPI NOR memory during boot. Limit accessible
>> + * size to 16MiB.
>> + */
>> + nor->addr_width = 3;
>> + mtd->size = 0x1000000;
>
> What if the device is smaller than 16 MiB?
>
> mtd->size = min(mtd->size, 0x1000000);

Not needed - this code is executed only for mtd->size > 0x1000000. See
bigger context:

if (info->addr_width)
nor->addr_width = info->addr_width;
else if (mtd->size > 0x1000000) {
/* enable 4-byte addressing if the device exceeds 16MiB */
nor->addr_width = 4;
if (JEDEC_MFR(info) == SNOR_MFR_SPANSION ||
info->flags & SPI_NOR_4B_OPCODES)
spi_nor_set_4byte_opcodes(nor, info);
else if (of_property_read_bool(np, "spi-3byte-addressing")) {
/*
* Do not enter 4byte mode in order to prevent
* the early bootloader to come up on non-default
* SPI NOR memory during boot. Limit accessible
* size to 16MiB.
*/
nor->addr_width = 3;
mtd->size = 0x1000000;
dev_info(dev, "Force 3B addressing mode\n");
} else
set_4byte(nor, info, 1);
} else {
nor->addr_width = 3;
}


Best regards,
Marcin