Re: [RFC] Accessing QSPI device under mtd

[Vignesh Raghavendra <vigneshr@ti.com>]

On 11/2/20 8:33 AM, Dinh Nguyen wrote:
> 
> 
> On 10/31/20 12:24 AM, Vignesh Raghavendra wrote:
>>
>>
>> On 10/31/20 12:53 AM, Dinh Nguyen wrote:
>>> Hi Vignesh,
>>>
>>> I'm using the standard arm64 defconfig. Attached are 2 bootlogs, v5.8
>>> and v5.9. On the v5.8, I can see the QSPI devices under /dev/mtdX, and
>>> has this in the bootlog:
>>>
>>> [    1.073562] cadence-qspi ff8d2000.spi: mt25qu02g (262144 Kbytes)
>>> [    1.079865] 2 fixed-partitions partitions found on MTD device
>>> ff8d2000.spi.0
>>> [    1.086917] Creating 2 MTD partitions on "ff8d2000.spi.0":
>>> [    1.092401] 0x000000000000-0x000003fe0000 : "Boot and fpga data"
>>> [    1.103073] 0x000003fe0000-0x000010000000 : "Root Filesystem - JFFS2"
>>>
>>> In v5.9, I don't see the above output in the bootlog, and there are no
>>> /dev/mtdX. I did a bisect and it resulted in commit "a314f6367787ee mtd:
>>> spi-nor: Convert cadence-quadspi to use spi-mem framework". If I revert
>>> this patch, then QSPI device is under /dev/mtdX.
>>>
>>> There were no changes in the Stratix10 DTS files between v5.8 and v5.9
>>> that should have any affect on QSPI.
>>>
>>
>> I think I found the problem. Looking at
>> arch/arm64/boot/dts/altera/socfpga_stratix10_socdk.dts:
>>
>> 	&qspi {
>>         	...
>> 	        flash@0 {
>>         	        compatible = "n25q00a";
>> 			...
>> 		};
>> 	};
>>
>> Flash node is using non standard compatible "n25q00a". Per
>> Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt, SPI NOR flash
>> node must include "jedec,spi-nor" as compatible.
>>
>> Old driver under drivers/mtd/spi-nor/ worked because, it directly called
>> spi_nor_scan() w/o looking at compatible string.
>>
>> Could you try adding "jedec,spi-nor" to flash node's compatible list and
>> see if everything works?
>>
>>
> 
> Yes, that fixed it! I have a question though, if I also change it to
> "jedec,spi-nor" on the v5.8 kernel, prior to the spi-mem commit, I get
> this error:
> 
> [    1.075268] cadence-qspi ff8d2000.spi: unrecognized JEDEC id bytes:
> d0 5d 91 08 22 00
> [    1.083091] cadence-qspi ff8d2000.spi: Cadence QSPI NOR probe failed -2
> [    1.089761] cadence-qspi: probe of ff8d2000.spi failed with error -2
> 
> Do you know why that is?
> 

Hmm, that should not happen.. Flash nodes "compatible" line as no effect
with old driver (even deleting it won't matter). Is this change on top
of plain v5.8 or do you have some other changes to spi-nor or controller
driver?

Only way to debug would be to see difference in controller register
configuration with and without "jedec,spi-nor"