> -----Original Message-----
> From: Nori, Sekhar
> Sent: Tuesday, January 22, 2013 4:04 AM
>
> Rob,
>
> On 1/11/2013 5:53 AM, Robert Tivy wrote:
> > Added dsp clock definition, keyed to "davinci-rproc.0".
> >
> > Signed-off-by: Robert Tivy <rtivy@xxxxxx>
> > ---
> > arch/arm/mach-davinci/da850.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/arch/arm/mach-davinci/da850.c b/arch/arm/mach-
> davinci/da850.c
> > index 097fcb2..50107c5 100644
> > --- a/arch/arm/mach-davinci/da850.c
> > +++ b/arch/arm/mach-davinci/da850.c
> > @@ -375,6 +375,14 @@ static struct clk sata_clk = {
> > .flags = PSC_FORCE,
> > };
> >
> > +static struct clk dsp_clk = {
> > + .name = "dsp",
> > + .parent = &pll0_sysclk1,
> > + .domain = DAVINCI_GPSC_DSPDOMAIN,
> > + .lpsc = DA8XX_LPSC0_GEM,
> > + .flags = PSC_LRST,
> > +};
> > +
> > static struct clk_lookup da850_clks[] = {
> > CLK(NULL, "ref", &ref_clk),
> > CLK(NULL, "pll0", &pll0_clk),
> > @@ -421,6 +429,7 @@ static struct clk_lookup da850_clks[] = {
> > CLK("spi_davinci.1", NULL, &spi1_clk),
> > CLK("vpif", NULL, &vpif_clk),
> > CLK("ahci", NULL, &sata_clk),
> > + CLK("davinci-rproc.0", NULL, &dsp_clk),
>
> Adding this clock node without the having the driver probed leads to
> kernel hang while booting. With CONFIG_DAVINCI_RESET_CLOCKS=n, the
> kernel boot fine. It looks like there is some trouble disabling the
> clock if it is not used. Can you please check this issue?
>
> Thanks,
> Sekhar
Sekhar,
Thankyou for trying that out.
I discovered that the kernel boot hang is caused when trying to disable this clk during init, from within the function davinci_clk_disable_unused(). That function calls davinci_psc_config() which attempts to disable the DSP clock. Since this clk is enabled after reset, disabling it involves a state transition, and therefore the function must wait for GOSTAT[1] to be 0. For most peripherals this happens automatically, but for the DSP (and ARM, too), the DSP must execute the IDLE instruction to allow a clock enable->disable transition. Since this is bootup and there is no real program on the DSP yet, this doesn't happen.
I was able to overcome this by adding PSC_FORCE to the clk->flags for dsp_clk. In fact, without PSC_FORCE I was not able to "rmmod davinci_remoteproc" since the firmware file that I'm loading did not execute IDLE. It feels like for davinci we should have a way to control the clk->flags' PSC_FORCE setting at run-time. The PSC_FORCE would be set initially (during boot) and the user (or system integrator) would have a way to unset it dynamically. That way, when the DSP firmware does actually have a structured way to enter IDLE, the user can say "I'd like a structured shutdown" and unset PSC_FORCE (via a clean API). But for now I'm just going to turn on PSC_FORCE:
.flags = PSC_LRST | PSC_FORCE,
Thanks & Regards,
- Rob
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