linux-kernel - Re: [PATCH V2 2/4] clk: imx: imx8mq: use imx8m_clk_hw_composite

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Message-ID: <VI1PR04MB7023D08F2C9F97C293695A05EE370@VI1PR04MB7023.eurprd04.prod.outlook.com>
Date:   Wed, 15 Jan 2020 11:48:11 +0000
From:   Leonard Crestez <leonard.crestez@....com>
To:     Shawn Guo <shawnguo@...nel.org>, Peng Fan <peng.fan@....com>
CC:     Lucas Stach <l.stach@...gutronix.de>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Abel Vesa <abel.vesa@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Anson Huang <anson.huang@....com>, Jacky Bai <ping.bai@....com>
Subject: Re: [PATCH V2 2/4] clk: imx: imx8mq: use imx8m_clk_hw_composite_core

On 2020-01-15 1:12 PM, Shawn Guo wrote:
> On Tue, Jan 14, 2020 at 04:49:20PM +0000, Leonard Crestez wrote:
>> On 10.01.2020 09:17, Peng Fan wrote:
>>> From: Peng Fan <peng.fan@....com>
>>>
>>> Use imx8m_clk_hw_composite_core to simplify code.
>>>
>>> Reviewed-by: Abel Vesa <abel.vesa@....com>
>>> Signed-off-by: Peng Fan <peng.fan@....com>
>>> ---
>>>    drivers/clk/imx/clk-imx8mq.c | 19 +++++--------------
>>>    1 file changed, 5 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/drivers/clk/imx/clk-imx8mq.c b/drivers/clk/imx/clk-imx8mq.c
>>> index 4c0edca1a6d0..b031183ff427 100644
>>> --- a/drivers/clk/imx/clk-imx8mq.c
>>> +++ b/drivers/clk/imx/clk-imx8mq.c
>>> @@ -403,22 +403,13 @@ static int imx8mq_clocks_probe(struct platform_device *pdev)
>>>    
>>>    	/* CORE */
>>>    	hws[IMX8MQ_CLK_A53_SRC] = imx_clk_hw_mux2("arm_a53_src", base + 0x8000, 24, 3, imx8mq_a53_sels, ARRAY_SIZE(imx8mq_a53_sels));
>>> -	hws[IMX8MQ_CLK_M4_SRC] = imx_clk_hw_mux2("arm_m4_src", base + 0x8080, 24, 3, imx8mq_arm_m4_sels, ARRAY_SIZE(imx8mq_arm_m4_sels));
>>> -	hws[IMX8MQ_CLK_VPU_SRC] = imx_clk_hw_mux2("vpu_src", base + 0x8100, 24, 3, imx8mq_vpu_sels, ARRAY_SIZE(imx8mq_vpu_sels));
>>> -	hws[IMX8MQ_CLK_GPU_CORE_SRC] = imx_clk_hw_mux2("gpu_core_src", base + 0x8180, 24, 3,  imx8mq_gpu_core_sels, ARRAY_SIZE(imx8mq_gpu_core_sels));
>>> -	hws[IMX8MQ_CLK_GPU_SHADER_SRC] = imx_clk_hw_mux2("gpu_shader_src", base + 0x8200, 24, 3, imx8mq_gpu_shader_sels,  ARRAY_SIZE(imx8mq_gpu_shader_sels));
>>> -
>>>    	hws[IMX8MQ_CLK_A53_CG] = imx_clk_hw_gate3_flags("arm_a53_cg", "arm_a53_src", base + 0x8000, 28, CLK_IS_CRITICAL);
>>> -	hws[IMX8MQ_CLK_M4_CG] = imx_clk_hw_gate3("arm_m4_cg", "arm_m4_src", base + 0x8080, 28);
>>> -	hws[IMX8MQ_CLK_VPU_CG] = imx_clk_hw_gate3("vpu_cg", "vpu_src", base + 0x8100, 28);
>>> -	hws[IMX8MQ_CLK_GPU_CORE_CG] = imx_clk_hw_gate3("gpu_core_cg", "gpu_core_src", base + 0x8180, 28);
>>> -	hws[IMX8MQ_CLK_GPU_SHADER_CG] = imx_clk_hw_gate3("gpu_shader_cg", "gpu_shader_src", base + 0x8200, 28);
>>> -
>>>    	hws[IMX8MQ_CLK_A53_DIV] = imx_clk_hw_divider2("arm_a53_div", "arm_a53_cg", base + 0x8000, 0, 3);
>>> -	hws[IMX8MQ_CLK_M4_DIV] = imx_clk_hw_divider2("arm_m4_div", "arm_m4_cg", base + 0x8080, 0, 3);
>>> -	hws[IMX8MQ_CLK_VPU_DIV] = imx_clk_hw_divider2("vpu_div", "vpu_cg", base + 0x8100, 0, 3);
>>> -	hws[IMX8MQ_CLK_GPU_CORE_DIV] = imx_clk_hw_divider2("gpu_core_div", "gpu_core_cg", base + 0x8180, 0, 3);
>>> -	hws[IMX8MQ_CLK_GPU_SHADER_DIV] = imx_clk_hw_divider2("gpu_shader_div", "gpu_shader_cg", base + 0x8200, 0, 3);
>>> +
>>> +	hws[IMX8MQ_CLK_M4_DIV] = imx8m_clk_hw_composite_core("arm_m4_div", imx8mq_arm_m4_sels, base + 0x8080);
>>> +	hws[IMX8MQ_CLK_VPU_DIV] = imx8m_clk_hw_composite_core("vpu_div", imx8mq_vpu_sels, base + 0x8100);
>>> +	hws[IMX8MQ_CLK_GPU_CORE_DIV] = imx8m_clk_hw_composite_core("gpu_core_div", imx8mq_gpu_core_sels, base + 0x8180);
>>> +	hws[IMX8MQ_CLK_GPU_SHADER_DIV] = imx8m_clk_hw_composite("gpu_shader_div", imx8mq_gpu_shader_sels, base + 0x8200);
>>>    
>>>    	/* BUS */
>>>    	hws[IMX8MQ_CLK_MAIN_AXI] = imx8m_clk_hw_composite_critical("main_axi", imx8mq_main_axi_sels, base + 0x8800);
>>
>> Collapsing _SRC _CG into _DIV is an useful simplification but it
>> technically breaks DT compatibility rules.
>>
>> Inside imx8mq.dtsi there are clock assignments for
>> IMX8MQ_CLK_GPU_CORE_SRC and IMX8MQ_CLK_GPU_SHADER_SRC which no longer
>> exist so those assignments don't take effect.
> 
> We do not want to break existing DTBs for this case.  Patches dropped.

Sorry. I think DT compatibility could be maintained by adding 
assignments like this:

	hws[IMX8MQ_CLK_GPU_CORE_SRC] = hws[IMX8MQ_CLK_GPU_CORE_DIV];

If all the old clocks are aliased to the new composite then all 
currently valid set_rate and set_parent calls would still have the same 
effect.

It would also mean that you can set_rate on the mux and set_parent on 
the div but that should be harmless: an enhancement instead of a 
compat-breaking change.

--
Regards,
Leonard