Re: [RFC] Accessing QSPI device under mtd

[Dinh Nguyen <dinguyen@xxxxxxxxxx>]

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?

Thanks,
Dinh