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

[FUKAUMI Naoki]

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.

Best regards,

--
FUKAUMI Naoki
Radxa Computer (Shenzhen) Co., Ltd.

> Jimmy
>