linux-kernel - Re: [PATCH 4/6] clk: actions: Fix AHPPREDIV-H-AHB clock chain on Owl S500 SoC

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Message-ID: <20210316054547.GD1798@thinkpad>
Date:   Tue, 16 Mar 2021 11:15:47 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Cristian Ciocaltea <cristian.ciocaltea@...il.com>
Cc:     Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        Michael Turquette <mturquette@...libre.com>,
        Edgar Bernardi Righi <edgar.righi@...tec.org.br>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-actions@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 4/6] clk: actions: Fix AHPPREDIV-H-AHB clock chain on Owl
 S500 SoC

On Mon, Mar 08, 2021 at 07:18:29PM +0200, Cristian Ciocaltea wrote:
> There are a few issues with the setup of the Actions Semi Owl S500 SoC's
> clock chain involving AHPPREDIV, H and AHB clocks:
> 
> * AHBPREDIV clock is defined as a muxer only, although it also acts as
>   a divider.
> * H clock is defined as a standard divider, although the raw value zero
>   is not supported.

What do you mean by not supported? The datasheet lists "0" as the valid divisor
value for divide by 1.

Rest looks good to me.

Thanks,
Mani

> * AHB is defined as a multi-rate factor clock, but it is actually just
>   a fixed pass clock.
> 
> Let's provide the following fixes:
> 
> * Change AHBPREDIV clock to an ungated OWL_COMP_DIV definition.
> * Add a clock div table 'h_div_table' for the H clock to drop the
>   unsupported 0 rate and use the correct register shift value in the
>   OWL_DIVIDER definition.
> * Drop the unneeded 'ahb_factor_table[]' and change AHB clock to an
>   ungated OWL_COMP_FIXED_FACTOR definition.
> 
> Fixes: ed6b4795ece4 ("clk: actions: Add clock driver for S500 SoC")
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...il.com>
> ---
>  drivers/clk/actions/owl-s500.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/clk/actions/owl-s500.c b/drivers/clk/actions/owl-s500.c
> index abe8874353de..b9e434173b4f 100644
> --- a/drivers/clk/actions/owl-s500.c
> +++ b/drivers/clk/actions/owl-s500.c
> @@ -151,9 +151,9 @@ static struct clk_factor_table hde_factor_table[] = {
>  	{ 0, 0, 0 },
>  };
>  
> -static struct clk_factor_table ahb_factor_table[] = {
> -	{ 1, 1, 2 }, { 2, 1, 3 },
> -	{ 0, 0, 0 },
> +static struct clk_div_table h_div_table[] = {
> +	{ 1, 2 }, { 2, 3 }, { 3, 4 },
> +	{ 0, 0 },
>  };
>  
>  static struct clk_div_table rmii_ref_div_table[] = {
> @@ -184,7 +184,6 @@ static struct clk_div_table nand_div_table[] = {
>  
>  /* mux clock */
>  static OWL_MUX(dev_clk, "dev_clk", dev_clk_mux_p, CMU_DEVPLL, 12, 1, CLK_SET_RATE_PARENT);
> -static OWL_MUX(ahbprediv_clk, "ahbprediv_clk", ahbprediv_clk_mux_p, CMU_BUSCLK1, 8, 3, CLK_SET_RATE_PARENT);
>  
>  /* gate clocks */
>  static OWL_GATE(gpio_clk, "gpio_clk", "apb_clk", CMU_DEVCLKEN0, 18, 0, 0);
> @@ -197,16 +196,25 @@ static OWL_GATE(timer_clk, "timer_clk", "hosc", CMU_DEVCLKEN1, 27, 0, 0);
>  static OWL_GATE(hdmi_clk, "hdmi_clk", "hosc", CMU_DEVCLKEN1, 3, 0, 0);
>  
>  /* divider clocks */
> -static OWL_DIVIDER(h_clk, "h_clk", "ahbprediv_clk", CMU_BUSCLK1, 12, 2, NULL, 0, 0);
> +static OWL_DIVIDER(h_clk, "h_clk", "ahbprediv_clk", CMU_BUSCLK1, 2, 2, h_div_table, 0, 0);
>  static OWL_DIVIDER(apb_clk, "apb_clk", "ahb_clk", CMU_BUSCLK1, 14, 2, NULL, 0, 0);
>  static OWL_DIVIDER(rmii_ref_clk, "rmii_ref_clk", "ethernet_pll_clk", CMU_ETHERNETPLL, 1, 1, rmii_ref_div_table, 0, 0);
>  
>  /* factor clocks */
> -static OWL_FACTOR(ahb_clk, "ahb_clk", "h_clk", CMU_BUSCLK1, 2, 2, ahb_factor_table, 0, 0);
>  static OWL_FACTOR(de1_clk, "de_clk1", "de_clk", CMU_DECLK, 0, 4, de_factor_table, 0, 0);
>  static OWL_FACTOR(de2_clk, "de_clk2", "de_clk", CMU_DECLK, 4, 4, de_factor_table, 0, 0);
>  
>  /* composite clocks */
> +static OWL_COMP_DIV(ahbprediv_clk, "ahbprediv_clk", ahbprediv_clk_mux_p,
> +			OWL_MUX_HW(CMU_BUSCLK1, 8, 3),
> +			{ 0 },
> +			OWL_DIVIDER_HW(CMU_BUSCLK1, 12, 2, 0, NULL),
> +			0);
> +
> +static OWL_COMP_FIXED_FACTOR(ahb_clk, "ahb_clk", "h_clk",
> +			{ 0 },
> +			1, 1, CLK_SET_RATE_PARENT);
> +
>  static OWL_COMP_FACTOR(vce_clk, "vce_clk", hde_clk_mux_p,
>  			OWL_MUX_HW(CMU_VCECLK, 4, 2),
>  			OWL_GATE_HW(CMU_DEVCLKEN0, 26, 0),
> -- 
> 2.30.1
>