On Thu, Nov 09, 2023 at 12:47:06PM +0100, Ahmad Fatoum wrote: > From: Ahmad Fatoum <ah...@a3f.at> > > clk_get will return -EPROBE_DEFER if clock provider hasn't yet been > probed. In a system with deep probe enabled, dependencies are probed > on demand, so a -EPROBE_DEFER return is final and the console probe > will never succeed. > > CONFIG_DEBUG_LL is often used to debug this, but because the low-level > console is not interactive, it's a bit cumbersome. Improve upon this a > bit, by providing a clk_get_for_console helper that returns NULL if and > only if we are sure that a clock provider will not be probed. > > In that case, the driver can skip code paths initialization code and > baud rate setting dependent on having access to the clock and still > register a console that reuses what was set up by CONFIG_DEBUG_LL. > > Signed-off-by: Ahmad Fatoum <ah...@a3f.at> > --- > include/console.h | 26 ++++++++++++++++++++++++++ > include/linux/clk.h | 21 +++++++++++++++++++++ > 2 files changed, 47 insertions(+) > > diff --git a/include/console.h b/include/console.h > index 586b68f73301..b8c901801e9f 100644 > --- a/include/console.h > +++ b/include/console.h > @@ -8,6 +8,7 @@ > #define _CONSOLE_H_ > > #include <param.h> > +#include <linux/clk.h> > #include <linux/list.h> > #include <driver.h> > #include <serdev.h> > @@ -208,4 +209,29 @@ static inline void console_ctrlc_allow(void) { } > static inline void console_ctrlc_forbid(void) { } > #endif > > +/** > + * clk_get_for_console - get clock, ignoring known unavailable clock > controller > + * @dev: device for clock "consumer" > + * @id: clock consumer ID > + * > + * Return: a struct clk corresponding to the clock producer, a > + * valid IS_ERR() condition containing errno or NULL if it could > + * be determined that the clock producer will never be probed in > + * absence of modules. The NULL return allows serial drivers to > + * skip clock handling and rely on CONFIG_DEBUG_LL. > + */ > +static inline struct clk *clk_get_for_console(struct device *dev, const char > *id) > +{ > + struct clk *clk; > + > + if (!IS_ENABLED(CONFIG_DEBUG_LL)) > + return clk_get(dev, id);
There are several SoCs out there where the UART is enabled by the ROM already, on these we don't need to have CONFIG_DEBUG_LL enabled for a working UART. Maybe testing for the UART enable bit in probe() would be a better indication that the UART is already in a working state? Sascha > + > + clk = clk_get_if_available(dev, id); > + if (clk == NULL) > + dev_warn(dev, "couldn't get clock (ignoring)\n"); > + > + return clk; > +} > + > #endif > diff --git a/include/linux/clk.h b/include/linux/clk.h > index 61b4ff3127cf..f505f18a75c0 100644 > --- a/include/linux/clk.h > +++ b/include/linux/clk.h > @@ -14,6 +14,7 @@ > #include <linux/spinlock.h> > #include <linux/stringify.h> > #include <linux/container_of.h> > +#include <deep-probe.h> > #include <xfuncs.h> > > struct device; > @@ -982,4 +983,24 @@ static inline struct clk *clk_get_enabled(struct device > *dev, const char *id) > return clk; > } > > +/** > + * clk_get_if_available - get clock, ignoring known unavailable clock > controller > + * @dev: device for clock "consumer" > + * @id: clock consumer ID > + * > + * Return: a struct clk corresponding to the clock producer, a > + * valid IS_ERR() condition containing errno or NULL if it could > + * be determined that the clock producer will never be probed in > + * absence of modules. > + */ > +static inline struct clk *clk_get_if_available(struct device *dev, const > char *id) > +{ > + struct clk *clk = clk_get(dev, id); > + > + if (clk == ERR_PTR(-EPROBE_DEFER) && deep_probe_is_supported()) > + return NULL; > + > + return clk; > +} > + > #endif > -- > 2.39.2 > > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |