[v4] usb: uhci: Add clk support to uhci-platform

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Tue, 2018-01-16 at 11:36 +0300, Sergei Shtylyov wrote:
> Hello!
> 
> On 1/16/2018 12:53 AM, Benjamin Herrenschmidt wrote:
> 
> > > > The Aspeed SoCs use uhci-platform. With the new dynamic clock
> > > > control framework, the corresponding IP block clock must be
> > > > properly enabled.
> > > > 
> > > > This is a simplified variant of what ehci-platform does, it
> > > > looks for *one* clock attached to the device, and if it's
> > > > there, enables it.
> > > > 
> > > > Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> > > > Acked-by: Alan Stern <stern@rowland.harvard.edu>
> > > > ---
> > > > 
> > > > v4. Remove unnecessary NULL checks
> > > > 
> > > > v3. Fix tab vs. spaces and probe error path
> > > > 
> > > > v2. Don't forget to git add latest changes :-) This adds the
> > > >       part where we turn the clock off when removing the driver.
> > > > ---
> > > >    drivers/usb/host/uhci-hcd.h      |  3 +++
> > > >    drivers/usb/host/uhci-platform.c | 20 ++++++++++++++++++--
> > > >    2 files changed, 21 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/usb/host/uhci-hcd.h b/drivers/usb/host/uhci-hcd.h
> > > > index f1cc47292a59..7f9f33c8c232 100644
> > > > --- a/drivers/usb/host/uhci-hcd.h
> > > > +++ b/drivers/usb/host/uhci-hcd.h
> > > > @@ -4,6 +4,7 @@
> > > >    
> > > >    #include <linux/list.h>
> > > >    #include <linux/usb.h>
> > > > +#include <linux/clk.h>
> > > >    
> > > >    #define usb_packetid(pipe)	(usb_pipein(pipe) ? USB_PID_IN : USB_PID_OUT)
> > > >    #define PIPE_DEVEP_MASK		0x0007ff00
> > > > @@ -447,6 +448,8 @@ struct uhci_hcd {
> > > >    	int total_load;				/* Sum of array values */
> > > >    	short load[MAX_PHASE];			/* Periodic allocations */
> > > >    
> > > > +	struct clk *clk;			/* (optional) clock source */
> > > > +
> > > >    	/* Reset host controller */
> > > >    	void	(*reset_hc) (struct uhci_hcd *uhci);
> > > >    	int	(*check_and_reset_hc) (struct uhci_hcd *uhci);
> > > > diff --git a/drivers/usb/host/uhci-platform.c b/drivers/usb/host/uhci-platform.c
> > > > index 6cb16d4b2257..55c2d99bf7ec 100644
> > > > --- a/drivers/usb/host/uhci-platform.c
> > > > +++ b/drivers/usb/host/uhci-platform.c
> > > > @@ -89,6 +89,8 @@ static int uhci_hcd_platform_probe(struct platform_device *pdev)
> > > >    	if (!hcd)
> > > >    		return -ENOMEM;
> > > >    
> > > > +	uhci = hcd_to_uhci(hcd);
> > > > +
> > > >    	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > > >    	hcd->regs = devm_ioremap_resource(&pdev->dev, res);
> > > >    	if (IS_ERR(hcd->regs)) {
> > > > @@ -98,8 +100,6 @@ static int uhci_hcd_platform_probe(struct platform_device *pdev)
> > > >    	hcd->rsrc_start = res->start;
> > > >    	hcd->rsrc_len = resource_size(res);
> > > >    
> > > > -	uhci = hcd_to_uhci(hcd);
> > > > -
> > > >    	uhci->regs = hcd->regs;
> > > >    
> > > >    	/* Grab some things from the device-tree */
> > > > @@ -119,6 +119,19 @@ static int uhci_hcd_platform_probe(struct platform_device *pdev)
> > > >    				 "Enabled Aspeed implementation workarounds\n");
> > > >    		}
> > > >    	}
> > > > +
> > > > +	/* Get and enable clock if any specified */
> > > > +	uhci->clk = devm_clk_get(&pdev->dev, NULL);
> > > > +	if (IS_ERR(uhci->clk)) {
> > > > +		ret = PTR_ERR(uhci->clk);
> > > > +		goto err_rmr;
> > > > +	}
> > > > +	ret = clk_prepare_enable(uhci->clk);
> > > > +	if (ret) {
> > > > +		dev_err(&pdev->dev, "Error couldn't enable clock (%d)\n", ret);
> > > > +		goto err_rmr;
> > > > +	}
> > > > +
> > > >    	ret = usb_add_hcd(hcd, pdev->resource[1].start, IRQF_SHARED);
> > > >    	if (ret)
> > > >    		goto err_rmr;
> > > > @@ -127,6 +140,7 @@ static int uhci_hcd_platform_probe(struct platform_device *pdev)
> > > >    	return 0;
> > > >    
> > > >    err_rmr:
> > > > +	clk_disable_unprepare(uhci->clk);
> > > 
> > >       Really? You haven't enabled the clock before either *goto* above, why
> > > disable it here?
> > 
> > If clk is NULL or an error, disable will do nothing. The only case
> 
>     The rule of thumb was that you don't pass the error pointers to APIs but 
> indeed I'm now seeing the NULL check extended to the error pointers too...
> 
> > would be if enable at failed but then disable will do nothing in that
> > case.
> 
>     Are you sure there'll be no WARN_ON() triggered by clk_disable() with the 
> enable count == 0?

There is, and while we won't hit that on Aspeed as it won't fail, we
should probably make it right.

> > The above change was done at the suggestion of Alan. If you really
> 
>     I'd probably missed his mail.
> 
> > prefer I could add a clk_put and clearing of "clk" in the error path of
> > clk_prepare_enable, but that's about it.

I think the best is separate goto labels. I'll respin tomorrow.

Cheers,
Ben.
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