RE: [PATCH v2] clk: renesas: rcar-usb2-clock-sel: Add R-Car USB 2.0 clock selector PHY

Hi Geert-san,

From: Geert Uytterhoeven
Sent: Wednesday, July 5, 2017 7:09 PM

Hi Simoda-san,

On Wed, Jun 28, 2017 at 8:28 AM, Yoshihiro Shimoda
[off-list ref] wrote:

quoted

R-Car USB 2.0 controller can change the clock source from an oscillator
to an external clock via a register. So, this patch adds support
the clock source selector as a clock driver.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

Thanks for your patch!

Thank you very much for the comments!

quoted

--- /dev/null
+++ b/drivers/clk/renesas/rcar-usb2-clock-sel.c

quoted

+static void usb2_clock_sel_enable_extal_only(struct usb2_clock_sel_priv *priv)
+{
+       u16 val = readw(priv->base + USB20_CLKSET0);
+
+       pr_debug("%s: enter %d %d %x\n", __func__,
+                priv->extal, priv->xtal, val);
+
+       if (priv->extal && !priv->xtal && val != CLKSET0_EXTAL_ONLY)
+               writew(CLKSET0_EXTAL_ONLY, priv->base + USB20_CLKSET0);
+}
+
+static void usb2_clock_sel_disable_extal_only(struct usb2_clock_sel_priv *priv)
+{
+       if (priv->extal && !priv->xtal)
+               writew(CLKSET0_PRIVATE, priv->base + USB20_CLKSET0);
+}
+
+static int usb2_clock_sel_enable(struct clk_hw *hw)
+{
+       usb2_clock_sel_enable_extal_only(to_priv(hw));
+
+       return 0;
+}
+
+static void usb2_clock_sel_disable(struct clk_hw *hw)
+{
+       usb2_clock_sel_disable_extal_only(to_priv(hw));
+}
+
+/*
+ * This module seems a mux, but this driver assumes a gate because
+ * ehci/ohci platform drivers don't support clk_set_parent() for now.
+ * If this driver acts as a gate, ehci/ohci-platform drivers don't need
+ * any modification.
+ */
+static const struct clk_ops usb2_clock_sel_clock_ops = {
+       .enable = usb2_clock_sel_enable,
+       .disable = usb2_clock_sel_disable,
+};

So you do "smart muxing" in the enable routine above?

Yes.

quoted

+static int __init rcar_usb2_clock_sel_probe(struct platform_device *pdev)
+{
+       struct device *dev = &pdev->dev;
+       struct device_node *np = dev->of_node;
+       struct usb2_clock_sel_priv *priv;
+       struct resource *res;
+       struct clk *clk;
+       struct clk_init_data init;
+       int error;
+
+       priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+       if (!priv)
+               return -ENOMEM;
+
+       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+       priv->base = devm_ioremap_resource(dev, res);
+       if (IS_ERR(priv->base))
+               return PTR_ERR(priv->base);
+
+       priv->ehci_clk = devm_clk_get(dev, "ehci_ohci");
+       if (!IS_ERR(priv->ehci_clk)) {
+               error = clk_prepare_enable(priv->ehci_clk);
+               if (error)
+                       return error;
+       }
+
+       clk = devm_clk_get(dev, "usb_extal");
+       if (!IS_ERR(clk) && !clk_prepare_enable(clk)) {
+               priv->extal = !!clk_get_rate(clk);
+               clk_disable_unprepare(clk);
+       }
+       clk = devm_clk_get(dev, "usb_xtal");
+       if (!IS_ERR(clk) && !clk_prepare_enable(clk)) {
+               priv->xtal = !!clk_get_rate(clk);
+               clk_disable_unprepare(clk);
+       }
+
+       if (!priv->extal && !priv->extal) {
+               dev_err(dev, "This driver needs usb_extal or usb_xtal\n");
+               return -ENOENT;

Perhaps enabled clocks should be disabled on error?

Oops! I should call clk_disable_unprepare(priv->ehci_clk) here.
I will fix it.

quoted

+       }
+
+       platform_set_drvdata(pdev, priv);
+       dev_set_drvdata(dev, priv);
+
+       init.name = "rcar_usb2_clock_sel";
+       init.ops = &usb2_clock_sel_clock_ops;
+       init.flags = CLK_IS_BASIC;
+       init.parent_names = NULL;
+       init.num_parents = 0;
+       priv->hw.init = &init;
+
+       clk = clk_register(NULL, &priv->hw);
+       if (IS_ERR(clk))
+               return PTR_ERR(clk);

Likewise.

Same here. So, I will use "goto" for it.

quoted

+       error = of_clk_add_provider(np, of_clk_src_simple_get, clk);
+       if (error)
+               return error;
+
+       return 0;

return of_clk_add_provider(np, of_clk_src_simple_get, clk);

Thanks. I will fix it.

quoted

+/* Since this driver needs other ccf drivers, this uses subsys_initcall_sync */
+subsys_initcall_sync(rcar_usb2_clock_sel_init);

I suppose this is a workaround for the lack of probe deferral support in the
USB subsystem?

This is my fault. I added "power-domains" property into this device's node.
After I remove the power-domains like the cpg node, this driver can use subsys_initcall()
instead of subsys_initcall_sync().

Best regards,
Yoshihiro Shimoda

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds