Re: [PATCH 2/3] clk: bcm2835: register the BCM2711 GISB clock

[Florian Fainelli]

On 10/20/26 07:58, Nicolai Buchwitz wrote:
> The generator at CM offset 0x1d8 is not in any documentation I could
> find, but the firmware calls it gisb and runs it at 200 MHz off
> PLLD_PER with a 3.75 divider. GISB is the register bus of the STB
> peripherals, and on BCM2711 the GENET MDIO controller clocks its MDC
> from it. mdio-bcm-unimac wants that rate to work out the MDC period.
>
> Mark it critical. The firmware enables it at boot and nothing in Linux
> owns it, so it must never be gated.
>
> Checked on a Raspberry Pi CM4 by moving the divider at runtime, the
> MDIO busy time follows it.
>
> Signed-off-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>

Reviewed-by: Florian Fainelli <florian.fainelli@xxxxxxxxxxxx>

> ---
>   drivers/clk/bcm/clk-bcm2835.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
>
> diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
> index 118df86d717c6..bc1de20c7e00e 100644
> --- a/drivers/clk/bcm/clk-bcm2835.c
> +++ b/drivers/clk/bcm/clk-bcm2835.c
> @@ -117,6 +117,8 @@
>   #define CM_EMMCDIV		0x1c4
>   #define CM_EMMC2CTL		0x1d0
>   #define CM_EMMC2DIV		0x1d4
> +#define CM_GISBCTL		0x1d8
> +#define CM_GISBDIV		0x1dc

Yes, those names are correct and accurate here.
--
Florian