Re: [PATCH 1/4] CLK: ti: dra7: Initialize USB_DPLL

Tero Kristo
2013-08-02T10:57:30Z

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@ti.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