Re: [RFC PATCH v2 00/12] spi: cadence-quadspi: add PHY tuning support

[Miquel Raynal <miquel.raynal@bootlin.com>]

On 07/02/2026 at 00:58:03 +0530, Santhosh Kumar K <s-k6@ti.com> wrote:

> On 05/02/26 21:18, Miquel Raynal wrote:
>> Hi Santhosh,
>> 
>>> I am surprised by these numbers, I would expect these to get higher for
>>> SPI NANDs. I will test the series and report my observations, especially
>>> since there is also ODDR SPI NAND support now (in nand/next, should be
>>> part of my upcoming merge request to Linus for 6.19+1);
>> I just tested the series, here are some numbers I grabbed on TI AM62A7
>> LP SK with a Winbond W35N02 SPI NAND chip (so in the end very close to
>> your report):
>>   +-----------------+-----------+------------+
>>   | SPI NAND        | no tuning | PHY tuning |
>>   | Unit: MiB/s     |   25MHz   |   166MHz   |
>>   |-----------------+-----------+------------|
>>   | Octal SDR read  |   13.8    |    34.2    |
>>   |           write |    7.2    |    10.2    |
>>   |-----------------+-----------+------------|
>>   | Octal DTR read  |   21.2    |     N/A    |
>>   |           write |    9.0    |     N/A    |
>>   +-----------------+-----------+------------+
>> Please mind I used MiB/s and not MB/s (so kiB / 1024), I don't know
>> which one you used for measuring, as you marked MB, whereas the most
>> common unit seems to be MiB.
>> However PHY tuning failed in Octal DTR mode (your series applied on
>> top
>> of nand/next) with the following logs, can you have a look?
>> [    2.261647] spi-nand spi0.0: Winbond SPI NAND was found.
>> [    2.266956] spi-nand spi0.0: 128 MiB, block size: 256 KiB, page size: 4096, OOB size: 128
>> [    2.285257] cadence-qspi fc40000.spi: PHY tuning failed: -2
>> [    2.290835] spi-nand spi0.0: Failed to execute PHY tuning: -2
>
> Unfortunately, due to a known erratum in the Cadence controller, PHY DDR
> mode cannot be used with 2-byte addressing.
>
> Refer:
> Errata i2383: OSPI: 2-byte address is not supported in PHY DDR mode [1]
>
> As a result, the Cadence controller supports only the following
> operating modes:
>  - PHY DDR mode with 4-byte addressing
>  - PHY SDR mode
>  - TAP (non-PHY) DDR mode
>  - TAP (non-PHY) SDR mode

I do not think we have 4-byte addressing capabilities on SPI NAND chips,
esp. Winbond's chips. So there is a down side: the core will pick-up
Octal DTR modes rather than Octal SDR (with PHY) mode, which is not the
fastest mode. Maybe we can guess that once we have access to the max
(tuned PHY) spi frequency, with an extra flag in the driver indicating
that the PHY speed is not accessible in DTR mode. But this again
requires different handling between SPI NAND and SPI NOR, as SPI NOR
IIRC may have 4-byte addressing capabilities.

Thanks,
Miquèl