Re: [PATCH v3 3/4] dt-bindings: mmc: cdns,sd6hc: add SD6HC DDR50 read-path tuning
From: Krzysztof Kozlowski
Date: Fri Nov 06 2026 - 07:45:13 EST
On Fri, Nov 06, 2026 at 02:16:54PM +0800, tze.yee.ng@xxxxxxxxxx wrote:
> From: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>
>
> DDR50 has no CMD19 tuning, so the SD6HC read path must be centred by
> static, board/SoC-characterised PHY settings. Add three optional SD6HC
> properties for the extended-read DDR modes (SD DDR50 and eMMC DDR52):
>
> - cdns,ddr-read-dqs-delay: read-DQS delay as a count of DLL delay
> elements (0-255), each cdns,delay-element-ps wide, that centres the
> read eye (default 0).
> - cdns,ddr-no-lpbk-dqs: disable the loopback DQS read strobe and
> use the fabricated phony DQS instead. Loopback DQS is the recommended
> default; set this only on boards that need the phony DQS read path.
> - cdns,ddr-phony-dqs-timing: PHY_CTRL[9:4] phony DQS assertion timing.
> The driver derives this from the RE# pulse width; this property
> overrides the computed value for boards whose flight time shifts the
> DDR data return.
>
> Signed-off-by: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>
> ---
> Changes in v3:
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxxxxx>
Best regards,
Krzysztof