Re: [PATCHv6 6/8] usb: dwc2: gadget: Do not fail probe if there isn't a clock node

[Felipe Balbi]

Hi,

On Fri, Oct 31, 2014 at 10:20:06AM -0500, Dinh Nguyen wrote:
> >> @@ -339,7 +339,8 @@ static void dwc2_handle_wakeup_detected_intr(struct 
> >> dwc2_hsotg *hsotg)
> >>            }
> >>            /* Change to L0 state */
> >>            hsotg->lx_state = DWC2_L0;
> >> -          call_gadget(hsotg, resume);
> >> +          if (!IS_ERR(hsotg->clk))
> >> +                  call_gadget(hsotg, resume);
> > 
> > instead of exposing the clock detail to the entire driver, add IS_ERR()
> > checks to resume and suspend instead. In fact, NULL is a valid clock, so
> > you might as well:
> > 
> >     clk = clk_get(foo, bar);
> >     if (IS_ERR(clk))
> >             dwc->clk = NULL;
> >     else
> >             dwc->clk = clk;
> > 
> > Then you don't need any IS_ERR() checks sprinkled around the driver.
> 
> But we would still need to check for the clock before accessing gadget
> functionality right?
> 
>       if (dwc2->clk)
>               call_gadget();

Read my comment again. "NULL is a valid clock".  Look at what
clk_enable() does when a NULL pointer is passed:

static int __clk_enable(struct clk *clk)
{
        int ret = 0;

        if (!clk)
                return 0;

        if (WARN_ON(clk->prepare_count == 0))
                return -ESHUTDOWN;

        if (clk->enable_count == 0) {
                ret = __clk_enable(clk->parent);

                if (ret)
                        return ret;

                if (clk->ops->enable) {
                        ret = clk->ops->enable(clk->hw);
                        if (ret) {
                                __clk_disable(clk->parent);
                                return ret;
                        }
                }
        }

        clk->enable_count++;
        return 0;
}

int clk_enable(struct clk *clk)
{
        unsigned long flags;
        int ret;

        flags = clk_enable_lock();
        ret = __clk_enable(clk);
        clk_enable_unlock(flags);

        return ret;
}
EXPORT_SYMBOL_GPL(clk_enable);

> >> @@ -400,7 +401,8 @@ static void dwc2_handle_usb_suspend_intr(struct 
> >> dwc2_hsotg *hsotg)
> >>                    "DSTS.Suspend Status=%d HWCFG4.Power Optimize=%d\n",
> >>                    !!(dsts & DSTS_SUSPSTS),
> >>                    hsotg->hw_params.power_optimized);
> >> -          call_gadget(hsotg, suspend);
> >> +          if (!IS_ERR(hsotg->clk))
> >> +                  call_gadget(hsotg, suspend);
> >>    } else {
> >>            if (hsotg->op_state == OTG_STATE_A_PERIPHERAL) {
> >>                    dev_dbg(hsotg->dev, "a_peripheral->a_host\n");
> >> @@ -477,7 +479,8 @@ irqreturn_t dwc2_handle_common_intr(int irq, void *dev)
> >>    spin_lock(&hsotg->lock);
> >>  
> >>    if (dwc2_is_device_mode(hsotg))
> >> -          retval = s3c_hsotg_irq(irq, dev);
> >> +          if (!IS_ERR(hsotg->clk))
> >> +                  retval = s3c_hsotg_irq(irq, dev);
> > 
> > wait a minute, if there is no clock we don't call the gadget interrupt
> > handler ? Why ? Who will disable the IRQ line ?
> 
> This portion is no static int __clk_enable(struct clk *clk)

huh ? What I mean is that this has the potential of leaving that IRQ
line enabled. Imagine you don't have a clock and s3c_hsotg_irq() isn't
called, then a peripheral IRQ fires, since the handler isn't called, who
will clear the interrupt ?

-- 
balbi

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