Re: [PATCH] usb: gadget: udc-xilinx: Add clock support

[Felipe Balbi <balbi@kernel.org>]

Hi,

Shubhrajyoti Datta <shubhraj@xilinx.com> writes:
>> -----Original Message-----
>> From: Felipe Balbi <balbi@kernel.org>
>> Sent: Wednesday, August 18, 2021 3:24 PM
>> To: Shubhrajyoti Datta <shubhraj@xilinx.com>
>> Cc: linux-usb@vger.kernel.org; gregkh@linuxfoundation.org; Michal Simek
>> <michals@xilinx.com>; git <git@xilinx.com>
>> Subject: Re: [PATCH] usb: gadget: udc-xilinx: Add clock support
>> 
>> 
>> Hi,
>> 
>> Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com> writes:
>> > Currently the driver depends on the  bootloader to enable the clocks.
>> > Add support for clocking. The patch enables the clock at  probe and
>> > disables them at remove.
>> >
>> > Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
>> > ---
>> >  drivers/usb/gadget/udc/udc-xilinx.c | 24 ++++++++++++++++++++++++
>> >  1 file changed, 24 insertions(+)
>> >
>> > diff --git a/drivers/usb/gadget/udc/udc-xilinx.c
>> > b/drivers/usb/gadget/udc/udc-xilinx.c
>> > index fb4ffedd6f0d..30070a488c87 100644
>> > --- a/drivers/usb/gadget/udc/udc-xilinx.c
>> > +++ b/drivers/usb/gadget/udc/udc-xilinx.c
>> > @@ -11,6 +11,7 @@
>> >   * USB peripheral controller (at91_udc.c).
>> >   */
>> >
>> > +#include <linux/clk.h>
>> >  #include <linux/delay.h>
>> >  #include <linux/device.h>
>> >  #include <linux/dma-mapping.h>
>> > @@ -171,6 +172,7 @@ struct xusb_ep {
>> >   * @addr: the usb device base address
>> >   * @lock: instance of spinlock
>> >   * @dma_enabled: flag indicating whether the dma is included in the
>> > system
>> > + * @clk: pointer to struct clk
>> >   * @read_fn: function pointer to read device registers
>> >   * @write_fn: function pointer to write to device registers
>> >   */
>> > @@ -188,6 +190,7 @@ struct xusb_udc {
>> >  	void __iomem *addr;
>> >  	spinlock_t lock;
>> >  	bool dma_enabled;
>> > +	struct clk *clk;
>> >
>> >  	unsigned int (*read_fn)(void __iomem *);
>> >  	void (*write_fn)(void __iomem *, u32, u32); @@ -2092,6 +2095,26 @@
>> > static int xudc_probe(struct platform_device *pdev)
>> >  	udc->gadget.ep0 = &udc->ep[XUSB_EP_NUMBER_ZERO].ep_usb;
>> >  	udc->gadget.name = driver_name;
>> >
>> > +	udc->clk = devm_clk_get(&pdev->dev, "s_axi_aclk");
>> > +	if (IS_ERR(udc->clk)) {
>> > +		if (PTR_ERR(udc->clk) != -ENOENT) {
>> > +			ret = PTR_ERR(udc->clk);
>> > +			goto fail;
>> > +		}
>> > +
>> > +		/*
>> > +		 * Clock framework support is optional, continue on,
>> > +		 * anyways if we don't find a matching clock
>> > +		 */
>> > +		udc->clk = NULL;
>> 
>> should it be, though? Might be a good idea to add fixed-clock instances to the
>> boards still depending on clock framework. Maybe that can be done over time,
>> but worth considering anyhow.
>
> But for backward compatibility , I think it will be good to have the
> support instead of forcing the fixed-clock node.

you gotta explain that a little better. Care to do so?

-- 
balbi