linux-kernel - Re: [v8 PATCH] PM / devfreq: Add dynamic scaling for imx8m ddr controller

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Date:   Fri, 20 Dec 2019 08:10:21 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     linux-pm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        leonard.crestez@....com, myungjoo.ham@...sung.com,
        kyungmin.park@...sung.com
Subject: Re: [v8 PATCH] PM / devfreq: Add dynamic scaling for imx8m ddr
 controller

On 12/20/19 8:09 AM, Chanwoo Choi wrote:
> From: Leonard Crestez <leonard.crestez@....com>
> 
> Add driver for dynamic scaling the DDR Controller on imx8m chips. Actual
> frequency switching is implemented inside TF-A, this driver wraps the
> SMC calls and synchronizes the clk tree.
> 
> The DRAM clocks on imx8m have the following structure (abridged):
> 
>  +----------+       |\            +------+
>  | dram_pll |-------|M| dram_core |      |
>  +----------+       |U|---------->| D    |
>                  /--|X|           |  D   |
>    dram_alt_root |  |/            |   R  |
>                  |                |    C |
>             +---------+           |      |
>             |FIX DIV/4|           |      |
>             +---------+           |      |
>   composite:     |                |      |
>  +----------+    |                |      |
>  | dram_alt |----/                |      |
>  +----------+                     |      |
>  | dram_apb |-------------------->|      |
>  +----------+                     +------+
> 
> The dram_pll is used for higher rates and dram_alt is used for lower
> rates. The dram_alt and dram_apb clocks are "imx composite" and their
> parent can also be modified.
> 
> This driver will prepare/enable the new parents ahead of switching (so
> that the expected roots are enabled) and afterwards it will call
> clk_set_parent to ensure the parents in clock framework are up-to-date.
> 
> The driver relies on dram_pll dram_alt and dram_apb being marked with
> CLK_GET_RATE_NOCACHE for rate updates.
> 
> Signed-off-by: Leonard Crestez <leonard.crestez@....com>
> Acked-by: Chanwoo Choi <cw00.choi@...sung.com>
> [cw00.choi: Edit the COMPILE_TEST module dependency in Kconfig]
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
> Changes from v7:
> - Squash patch[1] to this patch
> [1] https://patchwork.kernel.org/patch/11303869/
> - [PATCH] PM / devfreq: imx8m-ddrc: Fix argument swap in error print

Applied it.

(snip)


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics