linux-kernel - Re: [RFC PATCH v2 10/12] spi: cadence-quadspi: implement PHY tuning algorithm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <875x8bgk7y.fsf@bootlin.com>
Date: Thu, 05 Feb 2026 18:42:57 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Santhosh Kumar K <s-k6@...com>
Cc: <broonie@...nel.org>,  <robh@...nel.org>,  <krzk+dt@...nel.org>,
  <conor+dt@...nel.org>,  <richard@....at>,  <vigneshr@...com>,
  <tudor.ambarus@...aro.org>,  <pratyush@...nel.org>,  <mwalle@...nel.org>,
  <linux-spi@...r.kernel.org>,  <devicetree@...r.kernel.org>,
  <linux-kernel@...r.kernel.org>,  <linux-mtd@...ts.infradead.org>,
  <praneeth@...com>,  <u-kumar1@...com>,  <p-mantena@...com>,
  <a-dutta@...com>
Subject: Re: [RFC PATCH v2 10/12] spi: cadence-quadspi: implement PHY tuning
 algorithm

On 13/01/2026 at 19:46:15 +0530, Santhosh Kumar K <s-k6@...com> wrote:

> Implement PHY tuning for SDR and DDR modes. PHY tuning calibrates RX
> and TX delay lines to find optimal timing for high-speed operation.
>
> Add DLL management functions:
> - cqspi_resync_dll(): Reset DLL and wait for lock
> - cqspi_set_dll(): Configure RX/TX delays (0-127)
>
> Add pre/post config functions that enable PHY mode during tuning and
> restore normal operation afterward. PHY mode consumes one dummy cycle,
> so adjust dummy count to maintain correct flash timing.
>
> SDR tuning uses 1D search across RX delays at fixed TX. Search for
> two valid windows at consecutive read_delay values, select the larger
> window, and use the midpoint.
>
> DDR tuning uses 2D search across RX and TX delays:
> - Primary and secondary RX boundary searches at different TX values
> - Binary search for gap boundaries within valid region
> - Temperature compensation with midpoint calculation
> - Systematic boundary searches using 4-step increments
>
> The DDR algorithm finds the four corners of the valid region, identifies
> gaps, calculates temperature-aware midpoints, and validates final settings.
>
> Signed-off-by: Santhosh Kumar K <s-k6@...com>

This commit is gold, thanks a lot for the details in the comments.

I have no authority on this part to acknowledge it formally, but I
believe this is great work. Looking forward to see it work in octal DTR
mode now ;-)

Thanks,
Miquèl