Subject: [PATCH V2 3/3] ARM: imx: source gpt per clk from OSC for system timer

From: [email-masked] (Shawn Guo)
Date: Wed, 10 Sep 2014 19:49:38 +0800

On Wed, Sep 10, 2014 at 07:43:41AM +0000, Anson.Huang at freescale.com wrote:
> diff --git a/arch/arm/mach-imx/clk-imx6q.c b/arch/arm/mach-imx/clk-imx6q.c index 4ee6e77a0fdf..3f0401e27b38 100644
> --- a/arch/arm/mach-imx/clk-imx6q.c
> +++ b/arch/arm/mach-imx/clk-imx6q.c
> @@ -245,6 +245,7 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
>         clk[IMX6QDL_CLK_PLL3_80M]  = imx_clk_fixed_factor("pll3_80m",  "pll3_usb_otg",   1, 6);
>         clk[IMX6QDL_CLK_PLL3_60M]  = imx_clk_fixed_factor("pll3_60m",  "pll3_usb_otg",   1, 8);
>         clk[IMX6QDL_CLK_TWD]       = imx_clk_fixed_factor("twd",       "arm",            1, 2);
> +       clk[IMX6QDL_CLK_GPT_3M]    = imx_clk_fixed_factor("gpt_3m",    "osc",            1, 8);
>         if (cpu_is_imx6dl()) {
>                 clk[IMX6QDL_CLK_GPU2D_AXI] = imx_clk_fixed_factor("gpu2d_axi", "mmdc_ch0_axi_podf", 1, 1);
>                 clk[IMX6QDL_CLK_GPU3D_AXI] = imx_clk_fixed_factor("gpu3d_axi", "mmdc_ch0_axi_podf", 1, 1); @@ -469,6 +470,13 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
> 
>         clk_register_clkdev(clk[IMX6QDL_CLK_ENET_REF], "enet_ref", NULL);
> 
> +       /*
> +        * The gpt_3m clock is not available on i.MX6Q TO1.0.  Let's point it
> +        * to clock gpt_ipg_per to ease the gpt driver code.
> +        */
> +       if (cpu_is_imx6q() && imx_get_soc_revision() == IMX_CHIP_REVISION_1_0)
> +               clk[IMX6QDL_CLK_GPT_3M] = clk[IMX6QDL_CLK_GPT_IPG_PER];
> +
>         if ((imx_get_soc_revision() != IMX_CHIP_REVISION_1_0) ||
>             cpu_is_imx6dl()) {
>                 clk_set_parent(clk[IMX6QDL_CLK_LDB_DI0_SEL], clk[IMX6QDL_CLK_PLL5_VIDEO_DIV]);
> 
> diff --git a/arch/arm/mach-imx/time.c b/arch/arm/mach-imx/time.c index bf92e5a351c0..c0ad839516b0 100644
> --- a/arch/arm/mach-imx/time.c
> +++ b/arch/arm/mach-imx/time.c
> @@ -312,10 +317,21 @@ static void __init _mxc_timer_init(int irq,
>         __raw_writel(0, timer_base + MXC_TCTL);
>         __raw_writel(0, timer_base + MXC_TPRER); /* see datasheet note */
> 
> -       if (timer_is_v2())
> -               tctl_val = V2_TCTL_CLK_PER | V2_TCTL_FRR | V2_TCTL_WAITEN | MXC_TCTL_TEN;
> -       else
> +       if (timer_is_v2()) {
> +               tctl_val = V2_TCTL_FRR | V2_TCTL_WAITEN | MXC_TCTL_TEN;
> +               if (clk_get_rate(clk_per) == V2_TIMER_RATE_OSC_DIV8) {
> 			/* Is the assumption corrrect ??? */
> [Anson] I am afraid that i.MX6Q TO1.0 can NOT meet it, as there is no gpt_3m available for i.MX6Q TO1.0, but we have it in dtb and clk driver. 
> 
> +                       tctl_val |= V2_TCTL_CLK_OSC_DIV8;
> +                       if (cpu_is_imx6dl() || cpu_is_imx6sx()) {
> +                               /* 24 / 8 = 3 MHz */
> +                               __raw_writel(7 << V2_TPRER_PRE24M, timer_base + MXC_TPRER);
> +                               tctl_val |= V2_TCTL_24MEN;
> +                       }
> +               } else {
> +                       tctl_val |= V2_TCTL_CLK_PER;
> +               }
> +       } else {
>                 tctl_val = MX1_2_TCTL_FRR | MX1_2_TCTL_CLK_PCLK1 | MXC_TCTL_TEN;
> +       }
> 
>         __raw_writel(tctl_val, timer_base + MXC_TCTL);
> 
> @@ -349,9 +365,13 @@ static void __init mxc_timer_init_dt(struct device_node *np)
>         WARN_ON(!timer_base);
>         irq = irq_of_parse_and_map(np, 0);
> 
> -       clk_per = of_clk_get_by_name(np, "per");
>         clk_ipg = of_clk_get_by_name(np, "ipg");
> 
> +       /* Try osc_per clock first, and fall back to per clock otherwise */
> +       clk_per = of_clk_get_by_name(np, "osc_per");
> +       if (!IS_ERR(clk_per))
> +               clk_per = of_clk_get_by_name(np, "per");
> +
> [Anson] For i.MX6Q TO1.0, there is no GPT_3M clock for GPT, but in dtb, there is osc_per, so clk_per will be initialized by osc_per, and the clk rate read in _mxc_timer_init function will be 3000000 and go to the GPT_3M clk source path, which will NOT work for i.MX6Q TO1.0.
> 

I had the following change for clk-imx6q.c as above.  Shouldn't it
handle the i.MX6Q TO1.0 case well?

	if (cpu_is_imx6q() && imx_get_soc_revision() == IMX_CHIP_REVISION_1_0)
		clk[IMX6QDL_CLK_GPT_3M] = clk[IMX6QDL_CLK_GPT_IPG_PER];

Shawn

>         _mxc_timer_init(irq, clk_per, clk_ipg);  }  CLOCKSOURCE_OF_DECLARE(mx1_timer, "fsl,imx1-gpt", mxc_timer_init_dt);
>