On Fri, Apr 20 2018, Boris Brezillon wrote: > Hi Neil, > > On Mon, 16 Apr 2018 09:42:30 +1000 > NeilBrown <n...@brown.name> wrote: > >> Winbond spi-nor flash 32MB and larger have an 'Extended Address >> Register' as one option for addressing beyond 16MB (Macronix >> has the same concept, Spansion has EXTADD bits in the Bank Address >> Register). >> >> According to section >> 8.2.7 Write Extended Address Register (C5h) >> >> of the Winbond W25Q256FV data sheet (256M-BIT SPI flash) >> >> The Extended Address Register is only effective when the device is >> in the 3-Byte Address Mode. When the device operates in the 4-Byte >> Address Mode (ADS=1), any command with address input of A31-A24 >> will replace the Extended Address Register values. It is >> recommended to check and update the Extended Address Register if >> necessary when the device is switched from 4-Byte to 3-Byte Address >> Mode. >> >> So the documentation suggests clearing the EAR after switching to >> 3-byte mode. Experimentation shows that the EAR is *always* one after >> the switch to 3-byte mode, so clearing the EAR is mandatory at >> shutdown for a subsequent 3-byte-addressed reboot to work. >> >> Note that some SOCs (e.g. MT7621) do not assert a reset line at normal >> reboot, so we cannot rely on hardware reset. The MT7621 does assert a >> reset line at watchdog-reset. >> >> Signed-off-by: NeilBrown <n...@brown.name> > > We should probably backport the fix. Can you add a Fixes and Cc-stable > tag?
It's a bit weird having Fixes when this isn't a regression, but I guess
it doesn't hurt.
I chose
Fixes: 59b356ffd0b0 ("mtd: m25p80: restore the status of SPI flash when
exiting")
as this patch it useless without that one.
I also fixed the comment and have resent.
Thanks,
NeilBrown
>
>> ---
>>
>> following a helpful discussion with Marek, I've revised the description
>> a little, and make the code change specific to winbond.
>> I've change the OP names to RDEAR and WREAR instead of RDXA and WRXA to
>> match names used in the Macronix documentation. Winbond documentation
>> doesn't provide abbreviated OP names.
>>
>> Thanks,
>> NeilBrown
>>
>>
>> drivers/mtd/spi-nor/spi-nor.c | 13 +++++++++++++
>> include/linux/mtd/spi-nor.h | 2 ++
>> 2 files changed, 15 insertions(+)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index d445a4d3b770..0d0af0acf8b9 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -284,6 +284,19 @@ static inline int set_4byte(struct spi_nor *nor, const
>> struct flash_info *info,
>> if (need_wren)
>> write_disable(nor);
>>
>> + if (!status && !enable &&
>> + JEDEC_MFR(info) == SNOR_MFR_WINBOND) {
>> + /* On Winbond W25Q256FV, leaving 4byte mode causes
>
> We use regular kernel-comment style in MTD:
>
> /*
> * blablabla
> */
>
> Thanks,
>
> Boris
>
>> + * the Extended Address Register to be set to 1, so all
>> + * 3-byte-address reads come from the second 16M.
>> + * We must clear the register to enable normal behavior.
>> + */
>> + write_enable(nor);
>> + nor->cmd_buf[0] = 0;
>> + nor->write_reg(nor, SPINOR_OP_WREAR, nor->cmd_buf, 1);
>> + write_disable(nor);
>> + }
>> +
>> return status;
>> default:
>> /* Spansion style */
>> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
>> index de36969eb359..e60da0d34cc1 100644
>> --- a/include/linux/mtd/spi-nor.h
>> +++ b/include/linux/mtd/spi-nor.h
>> @@ -62,6 +62,8 @@
>> #define SPINOR_OP_RDCR 0x35 /* Read configuration register
>> */
>> #define SPINOR_OP_RDFSR 0x70 /* Read flag status register */
>> #define SPINOR_OP_CLFSR 0x50 /* Clear flag status register */
>> +#define SPINOR_OP_RDEAR 0xc8 /* Read Extended Address
>> Register */
>> +#define SPINOR_OP_WREAR 0xc5 /* Write Extended Address
>> Register */
>>
>> /* 4-byte address opcodes - used on Spansion and some Macronix flashes. */
>> #define SPINOR_OP_READ_4B 0x13 /* Read data bytes (low frequency) */
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