[PATCH RFC 0/4] Add set_iofv() callback

[Michael Walle]

Hi Biju,

>> >> > As per section 8.14 on the AT25QL128A hardware manual[1],
>> >> > IO0..IO3 must be set to Hi-Z state for this flash for fast read
>> >> > quad IO.
>> >> > Snippet from HW manual section 8.14:
>> >> > The upper nibble of the Mode(M7-4) controls the length of the next
>> >> > FAST Read Quad IO instruction through the inclusion or exclusion of
>> >> > the first byte instruction code. The lower nibble bits of the
>> >> > Mode(M3-0) are don't care. However, the IO pins must be
>> >> > high-impedance before the falling edge of the first data out clock.
>> >>
>> >> I'm still not sure what you are trying to fix here. For any quad I/O
>> >> mode, the pins of the controller must be in hiZ during the data phase
>> >> on a read operation. Otherwise the flash couldn't send any data,
>> >> there would be two drivers for one signal. So being in hiZ state
>> >> should be the default and shouldn't depend on any connected flash.
>> >
>> > OK, I will make hiZ state as the default.
>> 
>> I still think this iofv setting is the wrong approach, though. Do you 
>> have
>> a link to the spi controller datasheet where I can look up what the
>> controller is doing.
> 
> Please find the below link.
> 
> https://www.renesas.com/eu/en/products/microcontrollers-microprocessors/rz-mpus/rzg2l-general-purpose-microprocessors-dual-core-arm-cortex-a55-12-ghz-cpus-and-single-core-arm-cortex-m33#overview

Thanks.

>> This seem to be a general problem with what we are sending during the
>> command phase and I'm curious why there wasn't more reports on non 
>> working
>> micron flashes for now.
> 
> 1-bit mode, we don't have any issue. Once we switch to 4-bit mode we 
> have this
> issue with micron MT25QU512A flash and we need to set the correct IO 
> fixed values.
> 
> Maybe others are testing with 1-bit mode and not testing the full 
> capability of the flash.
> 
>> 
>> >> You've mentioned the micron flash which needs a '1' on its hold/reset
>> >> pin.
>> >> I would have expected a fixup for this flash, not for the flash which
>> >> behaves normal.
>> >
>> > I will drop fixup for Renesas AT25QL128A  and will add fixup for
>> > micron flash.
>> 
>> btw, what will happen if you always use the {3,3,3,1} setting? I guess 
>> the
>> atmel flash will also work? because HiZ should mean "don't care"
>> from
>> the point of view of the flash.
> 
> With atmel flash if use {3,3,3,1} setting, I get below error.
> 
> root at smarc-rzg2ul:/cip-test-scripts# ./rpcif_t_001.sh
> [  144.078854] spi-nor spi1.0: spi-nor-generic (16384 Kbytes)
> [  144.120468] 2 fixed-partitions partitions found on MTD device spi1.0
> [  144.126982] Creating 2 MTD partitions on "spi1.0":
> [  144.133004] 0x000000000000-0x000000200000 : "boot"
> [  144.141879] 0x000000200000-0x000001000000 : "user"
> [  358.476963] jffs2: notice: (230) read_dnode: node CRC failed on 
> dnode at 0xdfe084: read 0x336ebbbc, calculated 0x961503c7
> [  358.488509] jffs2: notice: (230) read_dnode: node CRC failed on 
> dnode at 0xdfd118: read 0xff6a5df6, calculated 0x786a5df6
> [  358.502963] jffs2: notice: (230) read_dnode: node CRC failed on 
> dnode at 0xdfa2d4: read 0x1fc99948, calculated 0xbab22133
> [  358.515357] jffs2: notice: (230) read_dnode: node CRC failed on 
> dnode at 0xdf9368: read 0xffd184a7, calculated 0x3d184a7
> [  358.528175] jffs2: notice: (230) read_dnode: node CRC failed on 
> dnode at 0xdf6524: read 0x5deb2462, calculated 0xf8909c19

Strange. Can't make any sense of this at the moment.

>> > With iofv settings {3,3,3,3} (all pins on Hi-Z state) with Micron
>> > flash
>> > ----------------------------------------------------------------------
>> > -
>> >
>> > ./rpcif_t_001.sh
>> > [   37.950986] spi-nor spi1.0: unrecognized JEDEC id bytes: ff ff ff ff
>> > ff ff
>> 
>> As mentioned earlier, I suspect that HiZ on IO3 means low and the 
>> flash
>> will be in reset. Could you perhaps verify that by probing IO3?
>> I know that other flashes will *either* support RESET#/HOLD# or quad 
>> mode.
>> Thus I was saying, that we probably wont support that and the easiest 
>> fix
>> should be to disable this behavior for the atmel flash (there was nv
>> setting).
> 
> The fix up is invoked only for quad mode, I believe it is safe to add 
> fixup for micron flash
> As it is the one deviating from normal according to you, rather than 
> adding fixup
> for generic flash like ATMEL flash(Now Renesas flash)

Could you please try setting bit 4 in the Nonvolatile Configuration
Register (Table 7) and see if the problem goes away?

Also could you have a look at the schematics, does the IO3/RESET#
have a pull-up? If not, who is in control of driving the correct
value here? If it has a pull-up, I'm puzzled why you need any
other setting than HiZ.

The correct fix would be to the information about the missing
IO state in the "struct spi_mem_op". That is, what should be the
default values of all the IO lines which are unused. For example
if we have a 1s1s4s transaction, what should be the state of IO0,
IO2 and IO3 during the command and address phase. If we have a
1s2s2s, what should be the state of IO0 during the command phase
etc.

That can then be used within your driver to set the corresponding
IOFV values (for each spi-mem op).

But I'm not sure if other SPI controllers will support that, though.

-michael