Re: [PATCH v3 00/13] spi: cadence-quadspi: add PHY tuning support

[Miquel Raynal]

Hi Santhosh,

Very happy to see this v3! Looks pretty neat overall.

On 27/05/2026 at 23:25:14 +0530, Santhosh Kumar K <s-k6@xxxxxx> wrote:

> This series implements PHY tuning support for the Cadence QSPI controller
> to enable reliable high-speed operations. Without PHY tuning, controllers
> use conservative timing that limits performance. PHY tuning calibrates
> RX/TX delay lines to find optimal data capture timing windows, enabling
> operation up to the controller's maximum frequency.
>
> Background:
> High-speed SPI memory controllers require precise timing calibration for
> reliable operation. At higher frequencies, board-to-board variations make
> fixed timing parameters inadequate. The Cadence QSPI controller includes
> a PHY interface with programmable delay lines (0-127 taps) for RX and TX
> paths, but these require runtime calibration to find the valid timing
> window.
>
> Approach:
> Add SDR/DDR PHY tuning algorithms for the Cadence controller:
>
> SDR Mode Tuning (1D search):
>  - Searches for two consecutive valid RX delay windows
>  - Selects the larger window and uses its midpoint for maximum margin
>  - TX delay fixed at maximum (127) as it's less critical in SDR
>
> DDR Mode Tuning (2D search):
>  - Finds RX boundaries (rxlow/rxhigh) using TX window sweeps
>  - Finds TX boundaries (txlow/txhigh) at fixed RX positions
>  - Defines valid region corners and detects gaps via binary search
>  - Applies temperature compensation for optimal point selection
>  - Handles single or dual passing regions with different strategies
>
> Patch description:
> Infrastructure (1-5):
>  - Patch 1:   Extend spi-max-frequency DT binding to accept an optional
>               second value forming a [base-freq, max-freq] pair
>  - Patch 2:   Add cadence-specific cdns,phy-pattern-partition phandle for
>               NOR flash PHY tuning pattern location
>  - Patch 3:   Parse two-element spi-max-frequency in spi.c; adds
>               spi_device.base_speed_hz (0 when a single value is used,
>               keeping all existing DT fully compatible)
>  - Patch 4:   Add spi_mem_apply_base_freq_cap(), called from
>               spi_mem_exec_op() to cap non-PHY ops to base_speed_hz;
>               tuned ops bypass the cap because execute_tuning() marks
>               them with op->max_freq = max_speed_hz
>  - Patch 5:   Add execute_tuning callback to spi_controller_mem_ops and
>               spi_mem_execute_tuning() wrapper in SPI-MEM core
>
> Cadence QSPI Implementation (6-10):
>  - Patch 6:   Move cqspi_readdata_capture() earlier (preparatory)
>  - Patch 7:   Add DQS bit to cqspi_readdata_capture() (preparatory)
>  - Patch 8:   Add complete PHY tuning support: DLL management, pattern
>               verification (NOR via cdns,phy-pattern-partition phandle,
>               NAND via write-to-cache), SDR 1D and DDR 2D search
>               algorithms with temperature compensation, AM654-specific
>               execute_tuning entry point; base_speed_hz is cleared during
>               the tuning loop and restored unconditionally on return
>  - Patch 9:   Reject 2-byte-address DDR operations via a new
>               CQSPI_NO_2BYTE_ADDR_PHY_DDR quirk flag to work around
>               AM654 OSPI erratum i2383
>  - Patch 10:  Enable PHY for direct memory-mapped reads (aligned body
>               region only; unaligned head and tail run without PHY) and
>               for indirect writes >= 1 KB
>
> MTD core (11-13):
>  - Patch 11:  Integrate tuning in SPI-NAND probe; propagate the validated
>               frequency to all plane dirmaps (primary and secondary op
>               templates) and to the persistent write dirmap template
>  - Patch 12:  Extract spi_nor_spimem_get_read_op() helper (preparatory)
>  - Patch 13:  Integrate tuning in SPI-NOR probe; patch the dirmap op
>               template with the validated frequency; store the result in
>               nor->max_read_op so all subsequent reads (dirmap and direct)
>               pick up the tuned speed automatically
>
> Series dependency:
> Merge after:
> https://lore.kernel.org/linux-spi/20260527173736.2243004-1-s-k6@xxxxxx/T/#u

Isn't the DQS series a prerequisite as well? I sent it as an RFC, we can
definitely consider it for merge together with this series once
ready.

Link: https://lore.kernel.org/linux-mtd/20260205-winbond-nand-next-phy-tuning-v1-0-5e7d3976f0f1@xxxxxxxxxxx/

Do you confirm that you have "[PATCH DO NOT MERGE RFC 4/4] spi: cadence-qspi: Retrieve
DQS capability using the core helper" in your branch for the PHY tuning
series to work?

> Testing:
> This series was tested on TI's
> AM62Ax SK with OSPI NAND flash and
> AM62Px SK with OSPI NOR flash:
>
> Read throughput:
> |-------------------------------------|
> |           | without PHY | with PHY  |
> |-------------------------------------|
> | OSPI NOR  | 37.5 MB/s   | 216 MB/s  |

I am impressed by the SPI NOR improvement o_O

> |-------------------------------------|
> | OSPI NAND | 9.2 MB/s    | 35.1 MB/s |
> |-------------------------------------|

Was this tested in 8D-8D-8D mode?

> Write throughput:
> |-------------------------------------|
> |           | without PHY | with PHY  |
> |-------------------------------------|
> | OSPI NAND | 6 MB/s      | 9.2 MB/s  |
> |-------------------------------------|

Thanks,
Miquèl