Re: [PATCH 2/2] gpio: omap: save two lines by using devm_clk_get_prepared()

["Sverdlin, Alexander" <alexander.sverdlin@xxxxxxxxxxx>]

Hey Matti, how are you?

On Fri, 2024-12-13 at 14:16 +0200, Matti Vaittinen wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > 
> > We can drop the else branch if we get the clock already prepared using
> > the relevant helper.
> > 
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> > ---
> 
> Booting a beaglebone black with the linux-next from Today fails 
> (next-20241213). Enabling earlycon + debug yields below splat to be 
> printed to the console:
> 
> [    2.628019] ------------[ cut here ]------------
> [    2.632793] WARNING: CPU: 0 PID: 34 at drivers/clk/clk.c:1254 
> clk_core_enable+0xb4/0x1b0
> [    2.641156] Enabling unprepared l4-wkup-clkctrl:0008:18
> [    2.646530] Modules linked in:
> [    2.649688] CPU: 0 UID: 0 PID: 34 Comm: kworker/u4:3 Not tainted 
> 6.13.0-rc2-next-20241213-00002-gf2d4b29c8330 #15
> [    2.660256] Hardware name: Generic AM33XX (Flattened Device Tree)
> [    2.666531] Workqueue: events_unbound deferred_probe_work_func
> [    2.672553] Call trace:
> [    2.672570]  unwind_backtrace from show_stack+0x10/0x14
> [    2.680578]  show_stack from dump_stack_lvl+0x50/0x64
> [  7 2.685788]  dump_stack_lvl from __warn+0xc0/0x130
> [    2.690734]  __warn from warn_slowpath_fmt+0x80/0x1a0
> [    2.695944]  warn_slowpath_fmt from clk_core_enable+0xb4/0x1b0
> [    2.701963]  clk_core_enable from clk_core_enable_lock+0x18/0x2c
> [    2.708159]  clk_core_enable_lock from 
> sysc_enable_opt_clocks.part.9+0x28/0x84
> [    2.715611]  sysc_enable_opt_clocks.part.9 from 
> sysc_enable_module+0x254/0x2dc
> [    2.723052]  sysc_enable_module from sysc_runtime_resume+0x17c/0x1c0
> [    2.729599]  sysc_runtime_resume from __rpm_callback+0x4c/0x130
> [    2.735709]  __rpm_callback from rpm_callback+0x50/0x54
> [    2.741096]  rpm_callback from rpm_resume+0x614/0x660
> [    2.746304]  rpm_resume from __pm_runtime_resume+0x4c/0x64
> [    2.751960]  __pm_runtime_resume from __device_attach+0xd0/0x188
> [    2.758155]  __device_attach from bus_probe_device+0x88/0x8c
> or_thread from kthread+0x188/0x24c
> [    2.789476]  kthread from ret_from_fork+0x14/0x20
> [    2.794327] Exception stack(0xe0091fb0 to 0xe0091ff8)
> [    2.799528] 1fa0:                                     00000000 
> 00000000 00000000 00000000
> [    2.807947] 1fc0: 00000000 00000000 00000000 00000000 00000000 
> 00000000 00000000 00000000
> [    2.816365] 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [    2.823173] ---[ end trace 0000000000000000 ]---
> [    2.828070] ti-sysc 44e07000.target-module: Optional clocks failed 
> for enable: -108
> [    2.835998] ------------[ cut here ]------------
> 
> reverting
> b7bbaff8c1bc ("gpio: omap: save two lines by using devm_clk_get_prepared()")
> 
> fixes the boot for me.
> 
> 
> >    drivers/gpio/gpio-omap.c | 4 +---
> >    1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> > index 54c4bfdccf568..57d299d5d0b16 100644
> > --- a/drivers/gpio/gpio-omap.c
> > +++ b/drivers/gpio/gpio-omap.c
> > @@ -1449,13 +1449,11 @@ static int omap_gpio_probe(struct platform_device *pdev)
> >    	}
> >    
> >    	if (bank->dbck_flag) {
> > -		bank->dbck = devm_clk_get(dev, "dbclk");
> > +		bank->dbck = devm_clk_get_prepared(dev, "dbclk");
> >    		if (IS_ERR(bank->dbck)) {
> >    			dev_err(dev,
> >    				"Could not get gpio dbck. Disable debounce\n");
> >    			bank->dbck_flag = false;
> > -		} else {
> > -			clk_prepare(bank->dbck);
> >    		}
> >    	}
> >    
> 
> I can only spot a minor functional change. The code prior this commit 
> does not check the result of clk_prepare(), and does neither set 
> bank->dbck_flag = false; nor call clk_put();
> 
> Other than that, timing is likely to be changed. Not sure what is the 
> thing here.

The new code looks more correct, with the return code check from clk_prepare().
Could it be that two problems eliminated themselves in your case before? ;-)
Would it be possible for you to provide the logs with "initcall_debug" with
and without the patch in question?

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com