[OpenWrt-Devel] [PATCH] ramips: reset m25p80 when shutdown

[Dorian Schneltzer]

Hi!
On 11/11/2015 12:26 PM, Daniel Golle wrote:
> Hi!
>
> On Wed, Nov 11, 2015 at 06:53:33PM +0800, Weijie Gao wrote:
>> 2015-11-08 4:42 GMT+08:00 Shonn Lu <countrysideboy at qq.com>:
>>
>>> Signed-off-by: Shonn Lu <countrysideboy at qq.com>
>>> ---
>>>  .../0064-reset-m25p80-when-shutdown.patch          | 24
>>> ++++++++++++++++++++++
>>>  1 file changed, 24 insertions(+)
>>>  create mode 100644
>>> target/linux/ramips/patches-3.18/0064-reset-m25p80-when-shutdown.patch
>>>
>>> diff --git
>>> a/target/linux/ramips/patches-3.18/0064-reset-m25p80-when-shutdown.patch
>>> b/target/linux/ramips/patches-3.18/0064-reset-m25p80-when-shutdown.patch
>>> new file mode 100644
>>> index 0000000..76f916a
>>> --- /dev/null
>>> +++
>>> b/target/linux/ramips/patches-3.18/0064-reset-m25p80-when-shutdown.patch
>>> @@ -0,0 +1,24 @@
>>> +--- a/drivers/mtd/devices/m25p80.c
>>> ++++ b/drivers/mtd/devices/m25p80.c
>>> +@@ -319,6 +319,12 @@
>>> + {
>>> +       struct m25p     *flash = spi_get_drvdata(spi);
>>> +
>>> ++    //        play4fun: add spi flash reset code
>>> ++      flash->command[0] = 0x66;
>>> ++      spi_write(flash->spi, flash->command, 1);
>>> ++      flash->command[0] = 0x99;
>>> ++      spi_write(flash->spi, flash->command, 1);
>>> ++
>>> +       /* Clean up MTD stuff. */
>>> +       return mtd_device_unregister(&flash->mtd);
>>> + }
>>> +@@ -382,6 +388,8 @@
>>> +       .id_table       = m25p_ids,
>>> +       .probe  = m25p_probe,
>>> +       .remove = m25p_remove,
>>> ++      //      play4fun add shutdown method to reset spi flash
>>> ++      .shutdown = m25p_remove,
>>> +
>>> +       /* REVISIT: many of these chips have deep power-down modes,
which
>>> +        * should clearly be entered on suspend() to minimize power use.
>>> --
>>> 1.9.1
>>> _______________________________________________
>>> openwrt-devel mailing list
>>> openwrt-devel at lists.openwrt.org
>>> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
>>
>>
>> This is not enough for w25q256.
>> The Extended Address Register (EAR) must be cleared, or the higher half
>> 16MB may be accessed in 3-byte addressing mode, and this will cause a
boot
>> failure.
>
> At least on Macronix SPI chips, using 0x66, 0x99 to reset the chip is
> not nough as that will not clear the adressing-mode bits.
> Using 0xE9 (EX4B; exit 4-byte mode) instead fixes the issue eg. on
> MX25L256.
>
> Also note, that while it's helpful to find out the details by directly
> writing values to the SPI bus, this is probably not acceptable
> upstream.
>
> I reckon we'll need a generic shutdown function in spi-nor.c calling
> set_4byte(nor, info, 0)
> We can then use that in m25p_remove.
>
>
>
> Cheers
>
>
> Daniel
> _______________________________________________
> openwrt-devel mailing list
> openwrt-devel at lists.openwrt.org
> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
Daniel is right. I had the reboot problem on the ALL5003 Module, RT5350
based and with Macronix MX25L25635E. Since Ralink U-Boot can only boot
in 24bit mode, the SPI Flash needs to be re-setted to 24bit mode from
32bit mode in order to be able to boot. Macronix has released an
application note called "MX25L25635E 256Mb Serial Flash Application in
System Reset" on their homepage, regarding exact this problem. There, in
the introduction, they wrote: "MX25L25635E provides 24-bit and 32-bit
address modes by command definition. Once the device enters 32-bit
address mode by B7 command, command E9 or power-off cycle is required to
exit the 32-bit address mode. After the flash switches to 32-bit address
mode and the system executes a warm boot (power is not off during the
system reset), the flash memory will remain in 32-bit address mode and
will not be able to boot by 24-bit addressing. "

In order to fix the problem, I used the patch from Shonn Lu, but
modified. Instead of writing 0x66 and 0x99, I just wrote 0xE9. After
this, the reboot worked like a charm. I don't know if writing just 0xE9
is enough in order to reset Winbond SPI flash. But I can confirm that
just writing an 0xE9 solves the reboot problem on Macronix 32MB SPI Flash.

I have some Winbond 25Q256FV chips here, but I need to find the time to
replace the macronix on my all5003 by a winbond in order to test the
patch. Maybe next week.


Cheers,
Dorian
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