On Tue, Oct 09, 2012 at 12:36:53PM +0000, Philip, Avinash wrote:
> On Mon, Oct 08, 2012 at 19:09:51, Thierry Reding wrote:
> > On Mon, Oct 08, 2012 at 01:31:19PM +0000, Philip, Avinash wrote:
> > > On Tue, Oct 02, 2012 at 11:30:14, Thierry Reding wrote:
> > > > On Wed, Sep 26, 2012 at 04:57:42PM +0530, Philip, Avinash wrote:
> > [...]
> > > > > @@ -231,13 +290,56 @@ static int __devinit ecap_pwm_probe(struct platform_device *pdev)
> > > > > }
> > > > >
> > > > > pm_runtime_enable(&pdev->dev);
> > > > > +
> > > > > + /*
> > > > > + * Some platform has extra PWM-subsystem common config space
> > > > > + * and requires special handling of clock gating.
> > > > > + */
> > > > > + if (pdata && pdata->has_configspace) {
> > > > > + r = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> > > > > + if (!r) {
> > > > > + dev_err(&pdev->dev, "no memory resource defined\n");
> > > > > + ret = -ENODEV;
> > > > > + goto err_disable_clock;
> > > > > + }
> > > > > +
> > > > > + pc->config_base = devm_ioremap(&pdev->dev, r->start,
> > > > > + resource_size(r));
> > > > > + if (!pc->config_base) {
> > > > > + dev_err(&pdev->dev, "failed to ioremap() registers\n");
> > > > > + ret = -EADDRNOTAVAIL;
> > > > > + goto err_disable_clock;
> > > > > + }
> > > >
> > > > Isn't this missing a request_mem_region()? I assume you don't do that
> > > > here because you need the same region in the EHRPWM driver, right?
> > >
> > > request_mem_region() is avoided as this region is shared across PWM
> > > sub modules ECAP & EHRPWM.
> > >
> > > > This should be indication enough that the design is not right here.
> > > > I think we need a proper abstraction here. Can this not be done via
> > > > PM runtime support? If not, maybe this should be represented by
> > > > clock objects since the bit obviously enables a clock.
> > >
> > > It is not done as part of PM runtime as this is has nothing to
> > > do with clock tree of the SOC. The bits we were enabling here
> > > should consider as an enable of the individual sub module as
> > > part of IP integration. Hence we were handling these subsystem
> > > module enable in the driver itself.
> >
> > My point remains valid: you shouldn't be able to access the same
> > register through two different drivers. That's one of the reasons, if
> > not the only reasen, why the request_mem_region() function exists. I
> > think you should add some abstraction to provide this functionality to
> > the drivers. I assume that eventually there will be more than just the
> > PWM cores that require access to this register.
>
> Enabling of PWM sub modules from CONFIG space is only present in AM33xx
> as part of IP integration (ECAP, EHRPWM & EQEP).
>
> Enabling of sub modules (ECAP, EHRPWM & EQEP) should do in CONFIG space.
> Hence sub module drivers are accessing CONFIG space without reserving it
> Individually from drivers (request_mem_region()).
>
> Can you describe/point how it can be handled in a separate Abstraction layer
> as this is shared across ECAP, EHRPWM & EQEP (EQEP driver is not yet available).
Perhaps something like a global function to enable and disable the
clocks would be enough. You could for instance have a driver that
requests the config space memory region and provides this global
function so that it can be used by the ECAP, EHRPWM and EQEP.
A more elaborate scheme would possibly involve making the new device a
parent of the ECAP, EHRPWM and EQEP devices and have their drivers
lookup the parent to determine which configurator device to operate on.
Thierry
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