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

[Tero Kristo]

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@xxxxxx>
> > > ---
> > >    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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