Re: [PATCH v2] clk: samsung: exynos5420: Keep top G3D clocks enabled

[Sylwester Nawrocki <s.nawrocki@samsung.com>]

On 12/16/19 14:14, Marek Szyprowski wrote:
> In Exynos542x/5800 SoCs, the G3D leaf clocks are located in the G3D power
> domain. This is similar to the other hardware modules and their power
> domains. However there is one thing specific to G3D clocks hierarchy.
> Unlike other hardware modules, the G3D clocks hierarchy doesn't have any
> gate clock between the TOP part of the hierarchy and the part located in
> the power domain and some SoC internal busses are sourced directly from
> the TOP muxes. The consequence of this design if the fact that the TOP
> part of the hierarchy has to be enabled permanently to ensure proper
> operation of the SoC power related components (G3D power domain and
> Exynos Power Management Unit for system suspend/resume).
> 
> This patch adds an explicit call to clk_prepare_enable() on the last MUX
> in the TOP part of G3D clock hierarchy to keep it enabled permanently to
> ensure that the internal busses get their clock regardless of the main
> G3D clock enablement status.

> ---
> diff --git a/drivers/clk/samsung/clk-exynos5420.c b/drivers/clk/samsung/clk-exynos5420.c
> index 3a991ca1ee36..c9e5a1fb6653 100644
> --- a/drivers/clk/samsung/clk-exynos5420.c
> +++ b/drivers/clk/samsung/clk-exynos5420.c

> @@ -1646,6 +1647,13 @@ static void __init exynos5x_clk_init(struct device_node *np,
>  				     exynos5x_subcmus);
>  	}
>  
> +	/*
> +	 * Keep top part of G3D clock path enabled permanently to ensure
> +	 * that the internal busses get their clock regardless of the
> +	 * main G3D clock enablement status.
> +	 */
> +	clk_prepare_enable(__clk_lookup("mout_sw_aclk_g3d"));
> +
>  	samsung_clk_of_add_provider(np, ctx);
>  }

It's a bit unfortunate we don't store that clock in the driver internally,
which would let us avoid the __clk_lookup() call. I can't come up with any
simple alternative though so let's apply it for now.

Acked-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

I don't have any other bug fix patches for clk/samsung, could you take it 
directly into your tree Stephen? 

-- 
Thanks,
Sylwester