linux-kernel - Re: [PATCH 1/4] CLK: ti: dra7: Initialize USB

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Message-ID: <51FB9095.8030200@ti.com>
Date:	Fri, 2 Aug 2013 13:57:25 +0300
From:	Tero Kristo <t-kristo@...com>
To:	Roger Quadros <rogerq@...com>
CC:	Nishanth Menon <nm@...com>, <tony@...mide.com>, <rnayak@...com>,
	<benoit.cousson@...aro.org>, <balbi@...com>,
	<george.cherian@...com>, <kishon@...com>, <dmurphy@...com>,
	<linux-omap@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] CLK: ti: dra7: Initialize USB_DPLL

On 08/02/2013 10:30 AM, Roger Quadros wrote:
> Hi Nishant,
>
> On 08/01/2013 06:06 PM, Nishanth Menon wrote:
>> On 08/01/2013 09:58 AM, Roger Quadros wrote:
>>> USB_DPLL must be initialized and locked at boot so that
>>> USB modules can work.
>>>
>>> Also program USB_DLL_M2 output to half rate.
>>>
>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>> ---
>>>    drivers/clk/omap/clk-7xx.c |   11 +++++++++++
>>>    1 files changed, 11 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/clk/omap/clk-7xx.c b/drivers/clk/omap/clk-7xx.c
>>> index ddb39dd..f444513 100644
>>> --- a/drivers/clk/omap/clk-7xx.c
>>> +++ b/drivers/clk/omap/clk-7xx.c
>>> @@ -19,6 +19,7 @@
>>>
>>>    #define DRA7_DPLL_ABE_DEFFREQ                361267200
>>>    #define DRA7_DPLL_GMAC_DEFFREQ                1000000000
>>> +#define DRA7_DPLL_USB_DEFFREQ                960000000
>>>
>>>
>>>    static struct omap_dt_clk dra7xx_clks[] = {
>>> @@ -63,5 +64,15 @@ int __init dra7xx_clk_init(void)
>>>        if (rc)
>>>            pr_err("%s: failed to configure GMAC DPLL!\n", __func__);
>>>
>>> +    dpll_ck = clk_get_sys(NULL, "dpll_usb_ck");
>>> +    rc = clk_set_rate(dpll_ck, DRA7_DPLL_USB_DEFFREQ);
>>> +    if (rc)
>>> +        pr_err("%s: failed to configure USB DPLL!\n", __func__);
>>> +
>>> +    dpll_ck = clk_get_sys(NULL, "dpll_usb_m2_ck");
>>> +    rc = clk_set_rate(dpll_ck, DRA7_DPLL_USB_DEFFREQ/2);
>>> +    if (rc)
>>> +        pr_err("%s: failed to set USB_DPLL M2 OUT\n", __func__);
>>> +
>>>        return rc;
>>>    }
>>>
>> As I had mentioned on [1] - we are going to see similar needs keep popping up. there is no need to hack this up for even more peripherals :(
>>
>> http://marc.info/?l=linux-omap&m=137536803106017&w=2
>>
> The DPLLs need to be initialized irrespective of whether peripheral drivers are present or not.
> We have seen cases where the SoC fails to enter RETention if the DPLLS are not correctly
> configured.
>
> But I agree with you that we should be able to initialize it by specifying the initial rate via Clock Data.
>
> This patch can be removed when the appropriate feature is added in OMAP clock core.

... not OMAP clock core, I would say clock core. This is again a feature 
we can work with once we have initial support in place.

-Tero
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