Re: [PATCH v5 08/12] i3c: dw-i3c-master: Add ACPI core clock frequency quirk

[Frank Li]

On Wed, Jun 24, 2026 at 10:21:02AM +0000, Akhil R wrote:
> Some ACPI-enumerated devices like Tegra410 do not expose the controller
> core clock through the clk framework. Unlike device tree, ACPI on Arm does
> not model clock providers. The hardware is expected to have its clocks
> enabled by firmware before the OS takes over.
>
> Make the core clock optional and allow selected ACPI devices to provide the
> core clock rate through the "clock-frequency" _DSD property when the core
> clock is absent.
>
> Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/i3c/master/dw-i3c-master.c | 27 ++++++++++++++++++++++++---
>  1 file changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
> index 29030fd9594a..8e40d178d500 100644
> --- a/drivers/i3c/master/dw-i3c-master.c
> +++ b/drivers/i3c/master/dw-i3c-master.c
> @@ -242,6 +242,7 @@
>  /* List of quirks */
>  #define AMD_I3C_OD_PP_TIMING		BIT(1)
>  #define DW_I3C_DISABLE_RUNTIME_PM_QUIRK	BIT(2)
> +#define DW_I3C_ACPI_SKIP_CLK_RST	BIT(3)
>
>  struct dw_i3c_cmd {
>  	u32 cmd_lo;
> @@ -556,13 +557,33 @@ static void dw_i3c_master_set_intr_regs(struct dw_i3c_master *master)
>  	writel(IBI_REQ_REJECT_ALL, master->regs + IBI_MR_REQ_REJECT);
>  }
>
> +static unsigned long dw_i3c_master_get_core_rate(struct dw_i3c_master *master)
> +{
> +	unsigned int core_rate_prop;
> +
> +	if (master->core_clk)
> +		return clk_get_rate(master->core_clk);
> +
> +	if (!(master->quirks & DW_I3C_ACPI_SKIP_CLK_RST))
> +		dev_err(master->dev, "missing core clock\n");
> +		return 0;
> +	}
> +
> +	if (device_property_read_u32(master->dev, "clock-frequency", &core_rate_prop)) {
> +		dev_err(master->dev, "missing clock-frequency property\n");
> +		return 0;
> +	}
> +
> +	return core_rate_prop;
> +}
> +
>  static int dw_i3c_clk_cfg(struct dw_i3c_master *master)
>  {
>  	unsigned long core_rate, core_period;
>  	u32 scl_timing;
>  	u8 hcnt, lcnt;
>
> -	core_rate = clk_get_rate(master->core_clk);
> +	core_rate = dw_i3c_master_get_core_rate(master);
>  	if (!core_rate)
>  		return -EINVAL;
>
> @@ -615,7 +636,7 @@ static int dw_i2c_clk_cfg(struct dw_i3c_master *master)
>  	u16 hcnt, lcnt;
>  	u32 scl_timing;
>
> -	core_rate = clk_get_rate(master->core_clk);
> +	core_rate = dw_i3c_master_get_core_rate(master);
>  	if (!core_rate)
>  		return -EINVAL;
>
> @@ -1577,7 +1598,7 @@ int dw_i3c_common_probe(struct dw_i3c_master *master,
>  	if (IS_ERR(master->regs))
>  		return PTR_ERR(master->regs);
>
> -	master->core_clk = devm_clk_get_enabled(&pdev->dev, NULL);
> +	master->core_clk = devm_clk_get_optional_enabled(&pdev->dev, NULL);
>  	if (IS_ERR(master->core_clk))
>  		return PTR_ERR(master->core_clk);
>
> --
> 2.43.0
>