Re: [PATCH v1] arm64: dts: ti: k3-am62-verdin: Set MMC clock pins as OUTPUT

Francesco,

On 8/13/2026 10:58 AM, Mendez, Judith wrote:
> 
> 
> On 8/13/2026 10:47 AM, Francesco Dolcini wrote:
>> On Thu, Aug 13, 2026 at 10:45:35AM -0500, Mendez, Judith wrote:
>>> Hi Francesco,
>>>
>>> On 8/13/2026 8:22 AM, Francesco Dolcini wrote:
>>>> +Judith
>>>>
>>>> On Thu, Aug 13, 2026 at 11:24:58AM +0000, [email protected] wrote:
>>>>> Thank you for your contribution! Sashiko AI review found 1 
>>>>> potential issue(s) to consider:
>>>>> - [High] Setting MMC clock pins to PIN_OUTPUT disables the receiver 
>>>>> (RXACTIVE=0), which breaks the internal clock loopback required by 
>>>>> the MMC controller for read operations.
>>>>> -- 
>>>>>
>>>>> --- Patch [1]: [PATCH v1] arm64: dts: ti: k3-am62-verdin: Set MMC 
>>>>> clock pins as OUTPUT ---
>>>>> commit b7e315f9edd8f485234748a2f8e267539b5b0f30
>>>>> Author: Francesco Dolcini <[email protected]>
>>>>>
>>>>> arm64: dts: ti: k3-am62-verdin: Set MMC clock pins as OUTPUT
>>>>>
>>>>> This commit changes the MMC clock pins for the K3 AM62x Verdin module
>>>>> from PIN_INPUT to PIN_OUTPUT to match the TRM documentation, 
>>>>> effectively
>>>>> disabling the receiver (RXACTIVE = 0).
>>>>>
>>>>> Link: https://www.ti.com/lit/pdf/spruiv7 Rev. C: Table 12-246. 
>>>>> MMCSDi I/O Signals [0]
>>>>>
>>>>>> diff --git a/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi b/arch/ 
>>>>>> arm64/boot/dts/ti/k3-am62-verdin.dtsi
>>>>>> index e97b2b047d104..895b1b7dcac71 100644
>>>>>> --- a/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi
>>>>>> +++ b/arch/arm64/boot/dts/ti/k3-am62-verdin.dtsi
>>>>>> @@ -573,7 +573,7 @@ AM62X_IOPAD(0x15c, PIN_INPUT, 0)  /* (AB22) 
>>>>>> MDIO0_MDIO */ /* ETH_1_MDIO, SODIMM
>>>>>>        pinctrl_sdhci0: main-mmc0-default-pins {
>>>>>>            pinctrl-single,pins = <
>>>>>>                AM62X_IOPAD(0x220, PIN_INPUT,        0) /*  (Y3) 
>>>>>> MMC0_CMD  */
>>>>>> -            AM62X_IOPAD(0x218, PIN_INPUT,        0) /* (AB1) 
>>>>>> MMC0_CLK  */
>>>>>> +            AM62X_IOPAD(0x218, PIN_OUTPUT,       0) /* (AB1) 
>>>>>> MMC0_CLK  */
>>>>>
>>>>> [Severity: High]
>>>>> Does configuring this pin as PIN_OUTPUT disable the receiver 
>>>>> (RXACTIVE=0) and
>>>>> break the internal clock loopback?
>>>>>
>>>>> TI MMC controllers generally rely on this internal clock loopback 
>>>>> path to
>>>>> synchronize incoming data for read operations. While the TRM 
>>>>> documents the
>>>>> logical direction of the signal to the external card, disabling the 
>>>>> input
>>>>> receiver might lead to eMMC read failures and timeouts.
>>>>
>>>> Judith: is sashiko right on this?
>>> Changing to PIN_OUTPUT should not break anything for you on AM62x based
>>> board. By default the input buffer for CLK pin is not used, CLKLB input
>>> buffer is used instead. CLKLB input is already configured for you by
>>> default, you should not be modifying CLKLB for MMC0 nor MMC1.
>>>
>>> This logic does not apply for MMC2.
>>
>> What do you mean? that MMC2_CLK should stay as input?
> 
> Well, there is a reason MMC2 CLKLB pin is defined in pinmux nodes on TI
> boards (: By default, MMC2 CLKLB is disabled after reset unlike MMC0 and

Meant to say MMC2 CLKLB input buffer is disabled after reset by default,
as in, RX_ACTIVE=0.

> MMC1. If we do not enable it in software -> PIN_INPUT, then the MMCSD 
> loopback clock input would not work and your MMC2 would not work.
> 
> ~ Judith
>