From: Boris Brezillon <boris.brezillon@bootlin.com>
To: NeilBrown <neil@brown.name>
Cc: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>,
Marek Vasut <marek.vasut@gmail.com>,
David Woodhouse <dwmw2@infradead.org>,
Brian Norris <computersforpeace@gmail.com>,
Boris Brezillon <boris.brezillon@free-electrons.com>,
Richard Weinberger <richard@nod.at>,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mtd: spi-nor: clear Winbond Extended Address Reg on switch to 3-byte addressing.
Date: Fri, 20 Apr 2018 21:54:40 +0200 [thread overview]
Message-ID: <20180420215440.7b078f6c@bbrezillon> (raw)
In-Reply-To: <87sh7wrq8p.fsf@notabene.neil.brown.name>
Hi Neil,
On Mon, 16 Apr 2018 09:42:30 +1000
NeilBrown <neil@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 <neil@brown.name>
We should probably backport the fix. Can you add a Fixes and Cc-stable
tag?
> ---
>
> 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) */
next prev parent reply other threads:[~2018-04-20 19:54 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-08 7:04 [PATCH] mtd: spi-nor: clear Extended Address Reg on switch to 3-byte addressing NeilBrown
2018-04-08 10:53 ` Marek Vasut
2018-04-08 21:56 ` NeilBrown
2018-04-09 21:58 ` Marek Vasut
2018-04-10 1:05 ` NeilBrown
2018-04-10 23:20 ` Marek Vasut
2018-07-23 18:25 ` Brian Norris
2018-07-23 21:45 ` NeilBrown
2018-07-23 22:17 ` Brian Norris
2018-07-23 22:23 ` NeilBrown
2018-04-10 23:13 ` Marek Vasut
2018-04-15 23:42 ` [PATCH v2] mtd: spi-nor: clear Winbond " NeilBrown
2018-04-20 19:54 ` Boris Brezillon [this message]
2018-04-20 21:26 ` [PATCH v3] " NeilBrown
2018-04-20 21:57 ` Marek Vasut
2018-04-20 22:54 ` [PATCH v4] " NeilBrown
2018-04-22 17:22 ` Boris Brezillon
2018-04-20 21:28 ` [PATCH v2] " NeilBrown
2018-04-20 22:10 ` Boris Brezillon
2018-04-20 22:51 ` NeilBrown
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