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

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Date:	Fri, 2 Aug 2013 07:52:48 -0500
From:	Nishanth Menon <nm@...com>
To:	Tero Kristo <t-kristo@...com>
CC:	Roger Quadros <rogerq@...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 05:57 AM, Tero Kristo wrote:
> 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.

OK. /me gives up for now. but please squash this into your set.


-- 
Regards,
Nishanth Menon
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