Re: [PATCH V1 0/2] arm64: dts: qcom: lemans-evk: Update SDHC storage support via overlays

[Monish Chunara <monish.chunara@oss.qualcomm.com>]

On Thu, Mar 05, 2026 at 06:52:17AM +0200, Dmitry Baryshkov wrote:
> On Mon, Mar 02, 2026 at 08:13:01PM +0530, Monish Chunara wrote:
> > On Fri, Feb 27, 2026 at 10:07:33PM +0200, Dmitry Baryshkov wrote:
> > > On Fri, Feb 27, 2026 at 03:54:03PM +0530, Monish Chunara wrote:
> > > > This series updates the device tree configuration for the LeMans EVK
> > > > board to support dynamic selection between SD card and eMMC storage.
> > > > 
> > > > The LeMans EVK hardware supports either an SD card or eMMC, but the
> > > > interfaces are mutually exclusive as they share the same controller and
> > > > resources. Previously, SD card support was hardcoded in the main device
> > > > tree, preventing easy switching to eMMC.
> > > > 
> > > > This series refactors the SDHC configuration by:
> > > > 
> > > > 1. Moving the existing SD card configuration into a dedicated overlay.
> > > > 2. Adding a new overlay to support eMMC.
> > > > 3. Updating the common SDHC node in the SoC dtsi to include necessary
> > > > resources (clocks, register ranges) required by the eMMC configuration.
> > > > 
> > > > This allows the bootloader to apply the appropriate overlay based on the
> > > > desired storage medium.
> > > 
> > > Is there a default mode of operation / extension? If there is one,
> > > please define it in the base DT and override it in a single overlay
> > > rather than having two mutually exclusive overlays.
> > > 
> > 
> > The LeMans EVK has SD card slot onboard and eMMC support via a mezzanine card.
> > 
> > However, if SD card is configured to be a default case in plaform DT, some of
> > the properties like 'no-mmc' would conflict for eMMC use case which cannot be
> > deleted in an overlay file, and vice versa. To avoid such issues, definied
> > separate overlays for both which gets selected based on the actual connection on
> > the board.
> 
> What would be the result of not specifying the no-mmc in the base DT?
>

If 'no-mmc' is not specified for SD card use-case, then during boot-up, it
would unnecessarily attempt for eMMC and sdio paths which are not required and
can be optimized with this property. Hence it needs to be added for SD card
use-case.

If SD card is made default in SoC DT, these properties will conflict as per the
above explanation.

Regards,
Monish