[U-Boot] Macronix NOR_SPI and Quad I/O

[Bacrau, Dumitru]

Hi Andy,

I have double-checked the datasheets and indeed the Quad Page Program opcode for Macronix is 0x38 and not 0x32 like the U-Boot code has defined in CMD_QUAD_PAGE_PROGRAM.

My version of the code is similar to the current u-boot mainline, and it also has the WR_QPP flag. But its usage depends on another flag that never gets set, so basically I have never used Quad mode for writing in my testing.

In the latest U-Boot code from u-boot-spi the situation is similar, except the above parameter is retrieved from the U-Boot device tree parameter  "spi-tx-bus-width". But none of the device trees set that parameter to '4' so again the Quad mode is never used for writing anyway.

Note that Quad mode is very useful for reading, where it effectively quadruples the speed. But in case of writing, it only speeds up data transmission to the flash device, which then starts writing, and the host keeps polling it for completion. Because of this, there is not a lot to gain from using quad mode for writing.

Ideally we would need a way to convey that the Macronix devices use a different instruction opcode for quad writing. This could be in spi_flash_info structure or somewhere in the device tree.

Regards,
Radu

-----Original Message-----
From: Champ, Andy [mailto:andycham at amazon.co.uk] 
Sent: Monday, November 28, 2016 9:59 AM
To: Bacrau, Dumitru <dumitru.bacrau at intel.com>; Jagan Teki <jagan at openedev.com>
Cc: u-boot at lists.denx.de; jteki at openedev.com; radu.bacrau at gmail.com; clsee at altera.com
Subject: RE: [U-Boot] Macronix NOR_SPI and Quad I/O

Hi Radu,
As far as I am concerned there is no urgency at all.
I just happened to notice as I was looking through the code that the command does not agree with the Macronix device spec, and I thought I should tell someone! Our device does not support Quad I/O.

Thanks
Andy Champ

-----Original Message-----
From: Bacrau, Dumitru [mailto:dumitru.bacrau at intel.com] 
Sent: 28 November 2016 15:50
To: Champ, Andy <andycham at amazon.co.uk>; Jagan Teki <jagan at openedev.com>
Cc: u-boot at lists.denx.de; jteki at openedev.com; radu.bacrau at gmail.com; clsee at altera.com
Subject: RE: [U-Boot] Macronix NOR_SPI and Quad I/O

Hi guys,

I do have Macronix parts and Quad capability. Unfortunately I am not using the latest U-Boot code (but looks similar) and also I do not have much time today and tomorrow.

Would it be OK if you waited until Wednesday so I can investigate and test this? If it is urgent go ahead and do what you need to, then we can add Quad later.

Thanks,
Radu

-----Original Message-----
From: Champ, Andy [mailto:andycham at amazon.co.uk] 
Sent: Monday, November 28, 2016 4:00 AM
To: Jagan Teki <jagan at openedev.com>
Cc: u-boot at lists.denx.de; jteki at openedev.com; radu.bacrau at gmail.com; clsee at altera.com; Bacrau, Dumitru <dumitru.bacrau at intel.com>
Subject: Re: [U-Boot] Macronix NOR_SPI and Quad I/O

I don't have anything that does Quad IO, so I can't test it either.

I think the best thing to do is to disable it for the Macronix parts, and put a comment in the table explaining why. With any luck one day somebody somewhere will have a device with a Macronix chip and quad I/O, and they can do it properly.

If this sounds good I'll put a patch together, run it past our open source lawyers (I'm not allowed to just push!) and send it through.

Alternatively I could put together a patch that sets a different flag bit for Macronix Quad I/O and push that. The only thing is of course that I have no way to test it, and as we all know untested code never works.

Which way should I go?

Regards
Andy Champ
________________________________________
From: Jagan Teki <jagan at openedev.com>
Sent: 26 November 2016 03:13
To: Champ, Andy
Cc: u-boot at lists.denx.de; jteki at openedev.com; radu.bacrau at gmail.com; clsee at altera.com; dumitru.bacrau at intel.com
Subject: Re: [U-Boot] Macronix NOR_SPI and Quad I/O

On Fri, Nov 25, 2016 at 10:07 PM, Champ, Andy <andycham at amazon.co.uk> wrote:
> Hi all,
>
>
> in the table in drivers/mtd/spi/spi_flash_ids.c there is a flag WR_QPP set against Macronix devices (including the ones Dumitru is just adding).
>
>
> This is used when programming the devices on a 4-bit bus to select the command to use for programming - either CMD_QUAD_PAGE_PROGRAM (0x32) or CMD_PAGE_PROGRAM (0x2).
>
>
> The Macronix devices that I have a spec for do not mention command 0x32. Each of the devices that I have a spec for ( MX25L25635F MX25U51245G MX25V8035F and MX25V1635F ) use command 0x38 instead.

We need to fix this, till now no Macronix has been tested with QUAD I think, please send the suitable fix will review.

thanks!
--
Jagan Teki
Free Software Engineer | www.openedev.com U-Boot, Linux | Upstream Maintainer Hyderabad, India.