[PATCH v6 3/3] arm64: dts: rockchip: Add Radxa CM5 IO Board

[Jimmy Hon]

On Wed, Nov 5, 2025 at 11:09 PM FUKAUMI Naoki <naoki at radxa.com> wrote:
>
> Hi Jimmy,
>
> On 11/6/25 13:53, Jimmy Hon wrote:
> > On Wed, Nov 5, 2025 at 9:31 PM Dragan Simic <dsimic at manjaro.org> wrote:
> >
> > [ snip ]
> >
> >>
> >> With all that in mind, we should specify "no-mmc" here, because
> >> we're describing a microSD slot, instead of describing some hybrid
> >> MMC/microSD slot.  That also explains why the adapter sold by Radxa
> >> is described as not to be used with microSD card slots on SBCs.  I'd
> >> also like to hear is this adapter/eMMC chip combo recognized by the
> >> kernel when "no-mmc" is specified; it should fail.
> >>
> >> Actually, not specifying "no-mmc" here may result in some unforeseen
> >> issues with some (or perhaps many?) microSD cards, because the MMC
> >> drivers will treat them as MMC-capable devices and try to initialize
> >> them as such, which may cause all kinds of issues.  In fact, I'm not
> >> really sure that the MMC drivers are actually implemented in a way
> >> that avoids all possible issues with the storage controllers that
> >> are capable of both SD and MMC modes when neither of "no-sd" and
> >> "no-mmc" is specified in their DT nodes.
> >
> > Hybrid MMC and SD slots are pretty normal on USB card readers. So it's
> > normal for the host controller to figure out what kind of card is in
> > the slot.
> > https://uditagarwal.in/understanding-sd-sdio-and-mmc-interface/
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6ae3e537eab9f560b516b001eb89f0cd568bdced
> > was the commit that introduced the device tree properties. By the
> > wording of the commit message, these device tree properties are used
> > to indicate to the driver if the host controller hardware is capable
> > of MMC initialization or SD initialization.
> >
> > Since the host controller in the RK3588 is capable of all the modes,
> > these properties do not need to be specified.
> >
> > Since Radxa has the eMMC to uSD adapter, it makes sense Radxa would
> > want to configure their microSD card slot on their boards to be a
> > hybrid SD/MMC slot.
> >
> > Now, the more fun question is if the adapter can handle eMMC HS200
> > using the 4-bit bus?
>
> I added
>   mmc-hs200-1_8v;
>
> I got
>
> [  226.099510] mmc_host mmc1: Bus speed (slot 0) = 400000Hz (slot req
> 400000Hz, actual 400000HZ div = 0)
> [  226.546246] mmc_host mmc1: Bus speed (slot 0) = 49500000Hz (slot req
> 52000000Hz, actual 49500000HZ div = 0)
> [  226.546371] mmc_host mmc1: Bus speed (slot 0) = 198000000Hz (slot req
> 200000000Hz, actual 198000000HZ div = 0)
> [  226.656853] dwmmc_rockchip fe2c0000.mmc: Successfully tuned phase to 76
> [  226.657011] mmc1: error -110 whilst initialising MMC card
> [  226.671469] mmc_host mmc1: Bus speed (slot 0) = 300000Hz (slot req
> 300000Hz, actual 300000HZ div = 0)
> [  226.793733] mmc1: switch to bus width 4 failed
> [  226.798915] mmc1: mmc_select_hs200 failed, error -110
> [  226.799390] mmc1: error -110 whilst initialising MMC card
> [  226.811549] mmc_host mmc1: Bus speed (slot 0) = 200000Hz (slot req
> 200000Hz, actual 200000HZ div = 0)
> [  226.947518] mmc1: switch to bus width 4 failed
> [  226.954978] mmc1: mmc_select_hs200 failed, error -110
> [  226.955454] mmc1: error -110 whilst initialising MMC card
>
> I don't know if this is board-dependent.

I was hoping for too much.

In the "RK3588 Datasheet", under the "eMMC Interface", it specifically
lists support for HS400. However, for the "SD/MMC Interface", it only
mentions "SD3.0, MMC ver4.51", so the more performant eMMC modes are
not available on that interface.

Jimmy

>
> Best regards,
>
> --
> FUKAUMI Naoki
> Radxa Computer (Shenzhen) Co., Ltd.
>
> > Jimmy
> >
>
>