Re: [PATCH v3 02/10] usb: dwc3: qcom: Add support for selecting UTMI as reference clock

[Varadarajan Narayanan <varadarajan.narayanan@oss.qualcomm.com>]

On Sun, Sep 06, 2026 at 08:46:41AM +0400, George Moussalem via B4 Relay wrote:
> From: George Moussalem <george.moussalem@outlook.com>
>
> On many Qualcomm chipsets, the UTMI clock is used as the reference clock
> (ex. IPQ5018, IPQ6018, and IPQ9574 and more). Since moving to the new
> flattened snps-dwc3 model, it is no longer possible to pass the
> reference clock to the dwc3 core driver.
>
> The clock rate is used by the dwc3 core to compute the reference clock
> period and frame length adjustment. This is needed when the reference
> clock rate used computes values that deviate from the hardware defaults.
> Above mentioned SoCs require values different from the defaults and, as
> such, the core initializes with the wrong values which leads to
> non-functional USB operation.
>
> In Qualcomm chipsets, if available, the UTMI clock is used as the
> reference clock. Therefore, acquire the reference clock by name
> ('mock_utmi') and pass its clock rate to the core using the probe_data
> structure.
>
> Signed-off-by: George Moussalem <george.moussalem@outlook.com>

Reviewed-by: Varadarajan Narayanan <varadarajan.narayanan@oss.qualcomm.com>