Re: [PATCH 3/3] arm64: dts: qcom: sm8650: Enable UHS-I SDR50 and SDR104 SD card modes

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 11/26/25 2:20 AM, Vladimir Zapolskiy wrote:
> The restriction on UHS-I speed modes was added to all SM8650 platforms
> by copying it from SM8450 and SM8550 dtsi files, and it was an actually
> reproducible problem due to the overclocking of SD cards. Since the latter
> issue has been fixed in the SM8650 GCC driver, UHS-I speed modes are
> working fine on SM8650 boards, below is the test performed on SM8650-HDK:
> 
> SDR50 speed mode:
> 
>     mmc0: new UHS-I speed SDR50 SDHC card at address 0001
>     mmcblk0: mmc0:0001 00000 14.6 GiB
>      mmcblk0: p1
> 
>     % dd if=/dev/mmcblk0p1 of=/dev/null bs=1M count=1024
>     1024+0 records in
>     1024+0 records out
>     1073741824 bytes (1.1 GB, 1.0 GiB) copied, 24.8086 s, 43.3 MB/s
> 
>     SDR104 speed mode:
> 
>     mmc0: new UHS-I speed SDR104 SDHC card at address 59b4
>     mmcblk0: mmc0:59b4 USDU1 28.3 GiB
>      mmcblk0: p1
> 
>     % dd if=/dev/mmcblk0p1 of=/dev/null bs=1M count=1024
>     1024+0 records in
>     1024+0 records out
>     1073741824 bytes (1.1 GB, 1.0 GiB) copied, 12.9448 s, 82.9 MB/s
> 
> Unset the UHS-I speed mode restrictions from the SM8550 platform dtsi
> file, there is no indication that the SDHC controller is broken.
> 
> Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
> ---
>  arch/arm64/boot/dts/qcom/sm8650.dtsi | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/qcom/sm8650.dtsi b/arch/arm64/boot/dts/qcom/sm8650.dtsi
> index ebf1971b1bfb..1be709204cae 100644
> --- a/arch/arm64/boot/dts/qcom/sm8650.dtsi
> +++ b/arch/arm64/boot/dts/qcom/sm8650.dtsi
> @@ -4939,9 +4939,6 @@ &mc_virt SLAVE_EBI1 QCOM_ICC_TAG_ALWAYS>,
>  
>  			bus-width = <4>;
>  
> -			/* Forbid SDR104/SDR50 - broken hw! */

This comment wasn't even right.. it did forbid MMC_CAP_4_BIT_DATA
which seems to have knocked off UHS-I for good, but also MMC_CAP_MMC_HIGHSPEED
which isn't applicable to SD cards

in any case

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad