linux-kernel - Re: [PATCH 1/6] clk: sunxi: Add support for sun9i a80 usb clocks and resets

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Date:	Wed, 5 Nov 2014 11:09:12 +0100
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Chen-Yu Tsai <wens@...e.org>
Cc:	Kishon Vijay Abraham I <kishon@...com>,
	Mike Turquette <mturquette@...aro.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH 1/6] clk: sunxi: Add support for sun9i a80 usb clocks and
 resets

On Wed, Nov 05, 2014 at 06:02:35PM +0800, Chen-Yu Tsai wrote:
> >> +static void __init sunxi_usb_clk_setup(struct device_node *node,
> >> +                                    const struct usb_clk_data *data,
> >> +                                    spinlock_t *lock)
> >> +{
> >> +     struct clk_onecell_data *clk_data;
> >> +     struct usb_reset_data *reset_data;
> >> +     const char *clk_parent;
> >> +     const char *clk_name;
> >> +     void __iomem *reg;
> >> +     int qty;
> >> +     int i = 0;
> >> +     int j = 0;
> >> +
> >> +     reg = of_iomap(node, 0);
> >
> > of_io_request_and_map?
> 
> OK. About that, any recommended naming style for the 3rd argument?
> Maybe the driver name "clk_sun9i_usb"? Or just a generic name like
> "usb_clk"?
> 
> I'm asking now as we'll likely be changing the existing drivers to
> use it as well.

I don't really have a preference. Maybe the DT node name would be both
the easier and better solution.

[...]

> >> +static void __init sun9i_a80_usb_mod_setup(struct device_node *node)
> >> +{
> >> +     /* AHB1 gate must be enabled to access registers */
> >> +     struct clk *ahb = of_clk_get(node, 0);
> >> +
> >> +     WARN_ON(IS_ERR(ahb));
> >> +     clk_prepare_enable(ahb);
> >
> > Hmmmm. That look off.
> >
> > Why do you need the clock to be enabled all the time? Isn't the CCF
> > already taking care of enabling the parent clock whenever it needs to
> > access any register?
> 
> There are also resets in the same block. That and I couldn't get it
> working without enabling the clock beforehand.

Ah, right.

What happens if you just enable and disable the clocks in the
reset_assert and reset_deassert right before and after accessing the
registers?

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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