linux-kernel - Re: [PATCH] ARM: OMAP4: clock: Initialize USB DPLL

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Date:	Thu, 21 Mar 2013 16:12:35 +0200
From:	Roger Quadros <rogerq@...com>
To:	Roger Quadros <rogerq@...com>
CC:	<tony@...mide.com>, <balbi@...com>, <rnayak@...com>,
	<t-kristo@...com>, <linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, Paul Walmsley <paul@...an.com>
Subject: Re: [PATCH] ARM: OMAP4: clock: Initialize USB DPLL

+Paul

On 03/21/2013 03:48 PM, Roger Quadros wrote:
> If the bootloader doesn't configure USB DPLL (e.g. in u-boot,
> disable CONFIG_USB_EHCI_OMAP), then we get all sorts of problems
> like
> - division by zero errors at boot [1]
> - USB DPLL fails to enter locked state
> - USB EHCI Host is non functional
> - Device can't enter OFF mode
> 
> Initializing the USB DPLL fixes all these issues.
> 
> [1]
> 
> [    0.000000] clock: dpll_usb_ck failed transition to 'locked'
> [    0.000000] Division by zero in kernel.
> [    0.000000] [<c001b00c>] (unwind_backtrace+0x0/0xf0) from [<c02b2378>] (Ldiv0+0x8/0x10)
> [    0.000000] [<c02b2378>] (Ldiv0+0x8/0x10) from [<c041cf3c>] (clk_divider_set_rate+0x10/0x124)
> [    0.000000] [<c041cf3c>] (clk_divider_set_rate+0x10/0x124) from [<c041bfc4>] (clk_change_rate+0x3c/0xb4)
> [    0.000000] [<c041bfc4>] (clk_change_rate+0x3c/0xb4) from [<c041c028>] (clk_change_rate+0xa0/0xb4)
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  arch/arm/mach-omap2/cclock44xx_data.c |   19 +++++++++++++++++++
>  1 files changed, 19 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/mach-omap2/cclock44xx_data.c b/arch/arm/mach-omap2/cclock44xx_data.c
> index bfc46c1..6127bb9 100644
> --- a/arch/arm/mach-omap2/cclock44xx_data.c
> +++ b/arch/arm/mach-omap2/cclock44xx_data.c
> @@ -53,6 +53,12 @@
>   */
>  #define OMAP4_DPLL_ABE_DEFFREQ				98304000
>  
> +/*
> + * OMAP4450 TRM Rev X, section "3.6.3.9.5 DPLL_USB Preferred Settings"
> + * states it must be at 960MHz
> + */
> +#define OMAP4_DPLL_USB_DEFFREQ				960000000
> +
>  /* Root clocks */
>  
>  DEFINE_CLK_FIXED_RATE(extalt_clkin_ck, CLK_IS_ROOT, 59000000, 0x0);
> @@ -1729,6 +1735,19 @@ int __init omap4xxx_clk_init(void)
>  	omap2_clk_disable_autoidle_all();
>  
>  	/*
> +	 * Lock USB_DPLL to avoid issues with USB host and OFF mode
> +	 */
> +	rc = clk_set_rate(&dpll_usb_ck, OMAP4_DPLL_USB_DEFFREQ);
> +	if (rc) {
> +		pr_err("%s: failed to configure DPLL_USB: %d\n", __func__, rc);
> +	} else {
> +		rc = clk_set_rate(&dpll_usb_m2_ck, OMAP4_DPLL_USB_DEFFREQ/2);
> +		if (rc)
> +			pr_err("%s: failed to configure DPLL_USB_M2: %d\n",
> +								__func__, rc);
> +	}
> +
> +	/*
>  	 * On OMAP4460 the ABE DPLL fails to turn on if in idle low-power
>  	 * state when turning the ABE clock domain. Workaround this by
>  	 * locking the ABE DPLL on boot.
> 

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