Subject: Re: [PATCH 4/6] clk: stm32f4: Add I2S clock
To: gabriel.fernandez@st.com, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Russell King <linux@armlinux.org.uk>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>, Nicolas Pitre <nico@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>, andrea.merello@gmail.com
References: <1478523943-23142-1-git-send-email-gabriel.fernandez@st.com>
 <1478523943-23142-5-git-send-email-gabriel.fernandez@st.com>
Cc: devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
        kernel@stlinux.com, ludovic.barre@st.com, olivier.bideau@st.com,
        amelie.delaunay@st.com
From: Daniel Thompson <daniel.thompson@linaro.org>
Message-ID: <08ad0f8c-bcdf-4835-9f07-167e129604bd@linaro.org>
Date: Mon, 7 Nov 2016 14:14:55 +0000
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On 07/11/16 13:05, gabriel.fernandez@st.com wrote:
> From: Gabriel Fernandez <gabriel.fernandez@st.com>
>
> This patch introduces I2S clock for stm32f4 soc.
> The I2S clock could be derived from an external clock or from pll-i2s
>
> Signed-off-by: Gabriel Fernandez <gabriel.fernandez@st.com>
> ---
>  drivers/clk/clk-stm32f4.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/clk/clk-stm32f4.c b/drivers/clk/clk-stm32f4.c
> index 5fa5d51..b7cb359 100644
> --- a/drivers/clk/clk-stm32f4.c
> +++ b/drivers/clk/clk-stm32f4.c
> @@ -216,6 +216,7 @@ enum {
>  	SYSTICK, FCLK, CLK_LSI, CLK_LSE, CLK_HSE_RTC, CLK_RTC,
>  	PLL_VCO_I2S, PLL_VCO_SAI,
>  	CLK_LCD,
> +	CLK_I2S,

Sorry, this has just clicked and it applies to most of the other 
patches, but adding things to this list effectively extends the clock 
bindings (i.e. the list of valid "other" clocks access with a primary 
index of 1).

This list if a list of "arbitrary" constants by which DT periphericals 
can be linked to specific clocks.

So...

  1)  If a clock is introduced here we should update the clock binding
      documentations.

  2)  If no peripheral can connect to the clock (because it is internal
      to the clock gen logic and peripherals must connect to the gated
      version) it should not be included in this enum.

  3)  I failed to mention this when the four undocumented clocks
      (LSI, LSE, HSE_RTC and RTC) were added.

  4)  I *should* have added a comment explaining the above to the code.


>  	END_PRIMARY_CLK
>  };
>
> @@ -967,6 +968,8 @@ static struct clk_hw *stm32_register_cclk(struct device *dev, const char *name,
>
>  static const char *sdmux_parents[2] = { "pll48", "sys" };
>
> +static const char *i2s_parents[2] = { "plli2s-r", NULL };
> +
>  struct stm32f4_clk_data {
>  	const struct stm32f4_gate_data *gates_data;
>  	const u64 *gates_map;
> @@ -1005,7 +1008,7 @@ struct stm32f4_clk_data {
>
>  static void __init stm32f4_rcc_init(struct device_node *np)
>  {
> -	const char *hse_clk;
> +	const char *hse_clk, *i2s_in_clk;
>  	int n;
>  	const struct of_device_id *match;
>  	const struct stm32f4_clk_data *data;
> @@ -1038,6 +1041,7 @@ static void __init stm32f4_rcc_init(struct device_node *np)
>  	stm32f4_gate_map = data->gates_map;
>
>  	hse_clk = of_clk_get_parent_name(np, 0);
> +	i2s_in_clk = of_clk_get_parent_name(np, 1);

Again this looks like a change to the DT bindings.

Also does the code work if i2s_in_clk is NULL or as you hoping to get 
away with a not-backwards compatible change?


Daniel.


>
>  	clk_register_fixed_rate_with_accuracy(NULL, "hsi", NULL, 0,
>  			16000000, 160000);
> @@ -1053,6 +1057,12 @@ static void __init stm32f4_rcc_init(struct device_node *np)
>  	clks[PLL_VCO_SAI] = stm32f4_rcc_register_pll(pllsrc,
>  			&data->pll_data[2], &stm32f4_clk_lock);
>
> +	i2s_parents[1] = i2s_in_clk;
> +
> +	clks[CLK_I2S] =	clk_hw_register_mux_table(NULL, "i2s",
> +				i2s_parents, ARRAY_SIZE(i2s_parents), 0,
> +				base + STM32F4_RCC_CFGR, 23, 1, 0, NULL,
> +				&stm32f4_clk_lock);
>  	sys_parents[1] = hse_clk;
>  	clk_register_mux_table(
>  	    NULL, "sys", sys_parents, ARRAY_SIZE(sys_parents), 0,
>