linux-kernel - Re: [PATCH] clk: sunxi-ng: a31: Fix CLK_OUT

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Date:   Sat, 17 Feb 2018 14:54:16 +0100
From:   Philipp Rossak <embed3d@...il.com>
To:     Chen-Yu Tsai <wens@...e.org>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] clk: sunxi-ng: a31: Fix CLK_OUT_* clock ops



On 17.02.2018 14:05, Chen-Yu Tsai wrote:
> When support for the A31/A31s CCU was first added, the clock ops for
> the CLK_OUT_* clocks was set to the wrong type. The clocks are MP-type,
> but the ops was set for div (M) clocks. This went unnoticed until now.
> This was because while they are different clocks, their data structures
> aligned in a way that ccu_div_ops would access the second ccu_div_internal
> and ccu_mux_internal structures, which were valid, if not incorrect.
> 
> Furthermore, the use of these CLK_OUT_* was for feeding a precise 32.768
> kHz clock signal to the WiFi chip. This was achievable by using the parent
> with the same clock rate and no divider. So the incorrect divider setting
> did not affect this usage.
> 
> Commit 946797aa3f08 ("clk: sunxi-ng: Support fixed post-dividers on MP
> style clocks") added a new field to the ccu_mp structure, which broke
> the aforementioned alignment. Now the system crashes as div_ops tries
> to look up a nonexistent table.
> 
> Reported-by: Philipp Rossak <embed3d@...il.com>
> Fixes: c6e6c96d8fa6 ("clk: sunxi-ng: Add A31/A31s clocks")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
Tested-by: Philipp Rossak <embed3d@...il.com>
> ---
> 
> Philipp, can you give this a test and report if this fixes thing?
> I don't have any A31/A31s boards online to test this.
> 
Thanks!
That fixes that bug!

Philipp

> ---
>   drivers/clk/sunxi-ng/ccu-sun6i-a31.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu-sun6i-a31.c b/drivers/clk/sunxi-ng/ccu-sun6i-a31.c
> index 72b16ed1012b..3b97f60540ad 100644
> --- a/drivers/clk/sunxi-ng/ccu-sun6i-a31.c
> +++ b/drivers/clk/sunxi-ng/ccu-sun6i-a31.c
> @@ -762,7 +762,7 @@ static struct ccu_mp out_a_clk = {
>   		.features	= CCU_FEATURE_FIXED_PREDIV,
>   		.hw.init	= CLK_HW_INIT_PARENTS("out-a",
>   						      clk_out_parents,
> -						      &ccu_div_ops,
> +						      &ccu_mp_ops,
>   						      0),
>   	},
>   };
> @@ -783,7 +783,7 @@ static struct ccu_mp out_b_clk = {
>   		.features	= CCU_FEATURE_FIXED_PREDIV,
>   		.hw.init	= CLK_HW_INIT_PARENTS("out-b",
>   						      clk_out_parents,
> -						      &ccu_div_ops,
> +						      &ccu_mp_ops,
>   						      0),
>   	},
>   };
> @@ -804,7 +804,7 @@ static struct ccu_mp out_c_clk = {
>   		.features	= CCU_FEATURE_FIXED_PREDIV,
>   		.hw.init	= CLK_HW_INIT_PARENTS("out-c",
>   						      clk_out_parents,
> -						      &ccu_div_ops,
> +						      &ccu_mp_ops,
>   						      0),
>   	},
>   };
>