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

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Date:	Thu, 21 Mar 2013 15:55:32 +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>
Subject: Re: [PATCH] ARM: OMAP4: clock: Initialize USB DPLL

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"

4460 actually.

cheers,
-roger
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