| Message ID | 20230414152423.19842-2-ddrokosov@sberdevices.ru |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: meson: support Amlogic A1 USB OTG controller | expand |
Hi Dmitry, On Fri, Apr 14, 2023 at 5:24 PM Dmitry Rokosov <ddrokosov@sberdevices.ru> wrote: [...] > - priv->clk = devm_clk_get(dev, "xtal"); > + priv->clk = devm_clk_get_enabled(dev, "xtal"); Generally this works fine but I wouldn't recommend this approach if: - there's some required wait time after the clock has been enabled (see phy_meson_g12a_usb2_init - there's already some required wait time after triggering the reset) - clock gating (for power saving) is needed when the dwc3 driver is unloaded by the PHY driver is not In this case: just manually manage the clock in phy_meson_g12a_usb2_{init,exit} Best regards, Martin
On Sun, Apr 16, 2023 at 10:54:17PM +0200, Martin Blumenstingl wrote: > Hi Dmitry, > > On Fri, Apr 14, 2023 at 5:24 PM Dmitry Rokosov <ddrokosov@sberdevices.ru> wrote: > [...] > > - priv->clk = devm_clk_get(dev, "xtal"); > > + priv->clk = devm_clk_get_enabled(dev, "xtal"); > Generally this works fine but I wouldn't recommend this approach if: > - there's some required wait time after the clock has been enabled > (see phy_meson_g12a_usb2_init - there's already some required wait > time after triggering the reset) > - clock gating (for power saving) is needed when the dwc3 driver is > unloaded by the PHY driver is not > > In this case: just manually manage the clock in phy_meson_g12a_usb2_{init,exit} I'm sorry, but I'm not fully understanding your point. Currently, no sleeps are required for this clock and we don't have any logic for power saving (g12a phy_ops doesn't have power_on()/power_off() implementation). However, I believe all of your arguments make sense for the future development of the phy_meson_g12a_usb2 driver. Is that correct?
diff --git a/drivers/phy/amlogic/phy-meson-g12a-usb2.c b/drivers/phy/amlogic/phy-meson-g12a-usb2.c index 9d1efa0d9394..26b99fbe1026 100644 --- a/drivers/phy/amlogic/phy-meson-g12a-usb2.c +++ b/drivers/phy/amlogic/phy-meson-g12a-usb2.c @@ -315,7 +315,7 @@ static int phy_meson_g12a_usb2_probe(struct platform_device *pdev) if (IS_ERR(priv->regmap)) return PTR_ERR(priv->regmap); - priv->clk = devm_clk_get(dev, "xtal"); + priv->clk = devm_clk_get_enabled(dev, "xtal"); if (IS_ERR(priv->clk)) return PTR_ERR(priv->clk);
Previously, all Amlogic boards used the XTAL clock as the USB PHY input clock, and it did not need to be enabled as it was the default board clock. However, in new Amlogic SoCs such as the A1 family, USB PHY uses a gated clock, so it is necessary to enable this gated clock during probing. Signed-off-by: Dmitry Rokosov <ddrokosov@sberdevices.ru> --- drivers/phy/amlogic/phy-meson-g12a-usb2.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)