Messages in this thread | | | Date | Thu, 11 Dec 2014 17:17:09 +0100 | From | Janusz Użycki <> | Subject | Re: [PATCH v3] clk: Add PWM clock driver |
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Hi Philipp,
W dniu 2014-12-10 o 15:59, Philipp Zabel pisze: > Hi Janusz, > > thank you for the comments. > > Am Dienstag, den 09.12.2014, 17:49 +0100 schrieb Janusz Użycki: > [...] >>> [...] >>> + pwm = devm_pwm_get(&pdev->dev, NULL); >> NULL or clk_name ? > There's only one pwm input to the pwm-clock, so I see no need to use a > con_id here and require the pwm-names device tree property to be set.
OK
> >>> [...] >>> + if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate)) >>> + clk_pwm->fixed_rate = 1000000000 / pwm->period; >> You can use NSEC_PER_SEC instead of the hardcoded value. > Thanks, I'll fix that. > >>> + >>> + if (pwm->period != 1000000000 / clk_pwm->fixed_rate && >>> + pwm->period != DIV_ROUND_UP(1000000000, clk_pwm->fixed_rate)) { >>> + dev_err(&pdev->dev, >>> + "clock-frequency does not match pwm period\n"); >>> + return -EINVAL; >>> + } >> This can't prevent against buggy pwm driver (bad frequency) >> because there is not function to read the period back, ie. >> .pwm_config callback does not modify duty_ns and period_ns to real >> values indeed. > Of course, this is only to make sure that the clock-frequency and pwm > duty cycle are roughly the same.
OK, it looks good and simple.
>> There is the way to set directly >> pwm->period = NSEC_PER_SEC / clk_pwm>fixed_rate; >> instead of third argument (period_ns) of pwms. Although the argument is >> required >> (#pwm-cells >= 2 and *_xlate_* functions) it could be set to 0 in pwms. >> Such calculation should be right for most PWMs if they are clocked not >> faster >> than eg. 40MHz. Above div-round issue can appear but it also appears due >> to ns resolution. >> I can't point if this is the best solution for the future. >> >>> + >>> + ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period); >>> + if (ret < 0) >>> + return ret; >>> + >>> + clk_name = node->name; >>> + of_property_read_string(node, "clock-output-names", &clk_name); >>> + >>> + init.name = clk_name; >>> + init.ops = &clk_pwm_ops; >>> + init.flags = CLK_IS_ROOT; >> and what about CLK_IS_BASIC? > Yes, I'll add that. > >>> + init.num_parents = 0; >> Is it proof against suspend/resume race of pwm driver vs pwm-clock's >> customer? >> Otherwise chain of clocks can be broken. > Are there pwm drivers that disable pwm output in their suspend callback? > I don't think system wide suspend/resume ordering can protect against > that at all, since the two devices may be on completely different buses. > In that case it'd probably be best to use runtime pm to keep the pwm > activated until clk_disable/pwm_disable is called by the consumer. > > [...] >>> +static struct platform_driver clk_pwm_driver = { >>> + .probe = clk_pwm_probe, >> missing >> .remove = clk_pwm_remove, >> >>> + .driver = { >>> + .name = "pwm-clock", >>> + .owner = THIS_MODULE, >> .owner could be removed (not a problem now) > Will add and remove those, respectively. > >>> + .of_match_table = of_match_ptr(clk_pwm_dt_ids), >>> + }, >> Why doesn't mcp251x trigger probe of pwm-clock driver? >> The fixed-clock uses CLK_OF_DECLARE which defines .data >> of of_device_id instead of .probe. Unfortunately I'm not so much >> familiar with DT. >> Any idea? > Did you add "simple-bus" to the clocks node compatible? The pwm-clock > device tree node needs to be placed somewhere where of_platform_populate > will consider it.
Yeah, I've added simple-bus but then I also removed from the driver .of_match_table and added node = of_find_compatible_node(NULL, NULL, "pwm-clock") and of_node_put(node) in the probe. The probe wasn't called. still Your suggestion helped me a lot to undo the wrong experiment, thanks! Expressing somewhere meaning of "simple-bus" could be a nice step.
"fixed-clock" was probed without "simple-bus" as it uses CLK_OF_DECLARE (init section). Now the pwm-clk [v3 + .remove + CLK_IS_BASIC + debug messages] driver is probed. My debug messages on system start (the driver is built-in, not a module): clk_pwm_probe: node c7efb9dc clk_pwm_recalc_rate: freq 12000000
On "modprobe mcp251x" with the pwm-clock configured I get "BUG: scheduling while atomic: modprobe/1374/0x00000002" and the back-trace below. It doesn't appear if fixed-clock used. On "rmmod" I get similar issue below.
Do you investigate tags like MODULE_LICENSE("GPL v2"), author etc. for the driver?
thanks, Janusz
# modprobe mcp251x CAN device driver interface ------------[ cut here ]------------ ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1374 at drivers/clk/clk.c:77 clk_enable_lock+0x4c/0xc4() CPU: 0 PID: 1374 Comm: modprobe Not tainted 3.14.17 #276 Backtrace: [<c000c700>] (dump_backtrace) from [<c000c828>] (show_stack+0x18/0x1c) r6:c053be98 r5:c0338e94 r4:0000004d [<c000c810>] (show_stack) from [<c0212c28>] (dump_stack+0x20/0x28) [<c0212c08>] (dump_stack) from [<c0016ae0>] (warn_slowpath_common+0x6c/0x8c) [<c0016a74>] (warn_slowpath_common) from [<c0016b24>] (warn_slowpath_null+0x24/0x2c) r8:c7166000 r7:c05f8308 r6:00000025 r5:60000093 r4:c05f3f48 [<c0016b00>] (warn_slowpath_null) from [<c0338e94>] (clk_enable_lock+0x4c/0xc4) [<c0338e48>] (clk_enable_lock) from [<c033900c>] (clk_enable+0x14/0x34) r5:00000025 r4:c780b120 [<c0338ff8>] (clk_enable) from [<c0266664>] (auart_console_write+0x38/0xec) r5:00000025 r4:c7ae6c00 [<c026662c>] (auart_console_write) from [<c004dbf0>] (call_console_drivers+0x124/0x148) r8:c7166000 r7:c05f8308 r6:00000025 r5:c05f8af8 r4:c05de0b8 [<c004dacc>] (call_console_drivers) from [<c004dfbc>] (console_unlock+0x3a8/0x4c8) r7:c0603780 r6:00000086 r5:00000004 r4:00000025 [<c004dc14>] (console_unlock) from [<c004eb30>] (vprintk_emit+0x448/0x498) r10:00000000 r9:60000093 r8:c05f870a r7:00000004 r6:00000024 r5:00000001 r4:00000000 [<c004e6e8>] (vprintk_emit) from [<c004ebb8>] (printk+0x38/0x40) r10:c7ba4240 r9:bf02eb9c r8:00000009 r7:00000000 r6:c053be98 r5:c0338e94 r4:0000004d [<c004eb84>] (printk) from [<c0016aa4>] (warn_slowpath_common+0x30/0x8c) r3:00000000 r2:c0338e94 r1:0000004d r0:c04f57ac [<c0016a74>] (warn_slowpath_common) from [<c0016b24>] (warn_slowpath_null+0x24/0x2c) r8:c7135000 r7:c79fdc6c r6:c796de10 r5:60000093 r4:c05f3f48 [<c0016b00>] (warn_slowpath_null) from [<c0338e94>] (clk_enable_lock+0x4c/0xc4) [<c0338e48>] (clk_enable_lock) from [<c033900c>] (clk_enable+0x14/0x34) r5:00000000 r4:c780b0c0 [<c0338ff8>] (clk_enable) from [<c023a08c>] (mxs_pwm_enable+0x30/0x60) r5:00000000 r4:c780b0c0 [<c023a05c>] (mxs_pwm_enable) from [<c0238df0>] (pwm_enable+0x54/0x60) r7:bf02ef1c r6:c7b7fc00 r5:00000000 r4:c7ba4240 [<c0238d9c>] (pwm_enable) from [<c033c3cc>] (clk_pwm_enable+0x14/0x18) [<c033c3b8>] (clk_pwm_enable) from [<c0338894>] (__clk_enable+0x6c/0xa0) [<c0338828>] (__clk_enable) from [<c0339018>] (clk_enable+0x20/0x34) r5:60000013 r4:c7ba4240 [<c0338ff8>] (clk_enable) from [<bf02e574>] (mcp251x_can_probe+0xc0/0x3e8 [mcp251x]) r5:00b71b00 r4:00000000 [<bf02e4b4>] (mcp251x_can_probe [mcp251x]) from [<c02cfb34>] (spi_drv_probe+0x20/0x24) r10:c064387c r9:c7167efc r8:00000004 r7:bf02ef1c r6:bf02ef1c r5:00000000 r4:c7b7fc00 [<c02cfb14>] (spi_drv_probe) from [<c0270a0c>] (driver_probe_device+0xd4/0x224) [<c0270938>] (driver_probe_device) from [<c0270de4>] (__driver_attach+0x6c/0x90) r10:00000000 r8:c7167f48 r7:bf02ef1c r6:bf02ef1c r5:c7b7fc34 r4:c7b7fc00 [<c0270d78>] (__driver_attach) from [<c026f3e8>] (bus_for_each_dev+0x5c/0x98) r6:c0270d78 r5:c7167d80 r4:00000000 [<c026f38c>] (bus_for_each_dev) from [<c0270818>] (driver_attach+0x20/0x28) r7:00000000 r6:c05e454c r5:c7ba3300 r4:bf02ef1c [<c02707f8>] (driver_attach) from [<c026fea0>] (bus_add_driver+0xbc/0x1c8) [<c026fde4>] (bus_add_driver) from [<c02713d0>] (driver_register+0xa8/0xec) r7:bf031000 r6:00000018 r5:bf02ef58 r4:bf02ef1c [<c0271328>] (driver_register) from [<c02cf948>] (spi_register_driver+0x4c/0x60) r5:bf02ef58 r4:00000000 [<c02cf8fc>] (spi_register_driver) from [<bf031014>] (mcp251x_can_driver_init+0x14/0x1c [mcp251x]) [<bf031000>] (mcp251x_can_driver_init [mcp251x]) from [<c0008900>] (do_one_initcall+0x98/0x140) [<c0008868>] (do_one_initcall) from [<c006df20>] (load_module+0xb30/0xe74) r10:00000000 r8:c7167f48 r7:00000000 r6:00000018 r5:bf02ef58 r4:00000000 [<c006d3f0>] (load_module) from [<c006e488>] (SyS_init_module+0xcc/0xd4) r10:00000000 r9:c7166000 r8:c0009664 r7:00000080 r6:000a9628 r5:000a9a58 r4:00004e96 [<c006e3bc>] (SyS_init_module) from [<c0009500>] (ret_fast_syscall+0x0/0x2c) r6:000a9628 r5:000a9a58 r4:000a97e0 ---[ end trace 3f34e0dc194f915a ]--- ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1374 at drivers/clk/clk.c:78 clk_enable_lock+0x80/0xc4()
# rmmod mcp251x BUG: scheduling while atomic: rmmod/1387/0x00000002 Backtrace: [<c000c700>] (dump_backtrace) from [<c000c828>] (show_stack+0x18/0x1c) r6:c712ed80 r5:00000000 r4:00000000 [<c000c810>] (show_stack) from [<c0212c28>] (dump_stack+0x20/0x28) [<c0212c08>] (dump_stack) from [<c003e998>] (__schedule_bug+0x48/0x60) [<c003e950>] (__schedule_bug) from [<c0410998>] (__schedule+0x68/0x4e8) r4:00000000 [<c0410930>] (__schedule) from [<c04110fc>] (schedule+0x78/0x7c) r10:00000002 r9:c78ba000 r8:c7863df4 r7:7fffffff r6:c7862000 r5:00000000 r4:7fffffff [<c0411084>] (schedule) from [<c0410330>] (schedule_timeout+0x20/0x218) [<c0410310>] (schedule_timeout) from [<c04119c0>] (wait_for_common+0x104/0x1d4) r8:c7863df4 r7:7fffffff r6:c7862000 r5:00000000 r4:00000000 [<c04118bc>] (wait_for_common) from [<c0411b38>] (wait_for_completion+0x18/0x1c) r10:c05d9470 r8:c7ba3300 r7:c7863df4 r6:00000001 r5:00000000 r4:c711e1c0 [<c0411b20>] (wait_for_completion) from [<c002bff8>] (call_usermodehelper_exec+0x108/0x174) [<c002bef0>] (call_usermodehelper_exec) from [<c002c14c>] (call_usermodehelper+0x48/0x50) r7:c7b97000 r6:00000000 r5:00000000 r4:00000001 [<c002c104>] (call_usermodehelper) from [<c0216364>] (kobject_uevent_env+0x3b4/0x434) r4:00000000 [<c0215fb0>] (kobject_uevent_env) from [<c02163f8>] (kobject_uevent+0x14/0x18) r10:00000000 r9:c7862000 r8:c0009664 r7:c7863f3c r6:c715f280 r5:c05deb28 r4:c7ba3300 [<c02163e4>] (kobject_uevent) from [<c021537c>] (kobject_release+0x38/0x7c) [<c0215344>] (kobject_release) from [<c0214eb8>] (kobject_put+0x68/0x7c) r6:00000000 r5:bf02ef58 r4:c7ba3300 [<c0214e50>] (kobject_put) from [<c026f86c>] (bus_remove_driver+0x80/0x98) r4:bf02ef1c [<c026f7ec>] (bus_remove_driver) from [<c0271304>] (driver_unregister+0x48/0x54) r4:bf02ef1c [<c02712bc>] (driver_unregister) from [<bf02e8b0>] (mcp251x_can_driver_exit+0x14/0x1c [mcp251x]) r4:a0000013 [<bf02e89c>] (mcp251x_can_driver_exit [mcp251x]) from [<c006e5fc>] (SyS_delete_module+0x12c/0x194) [<c006e4d0>] (SyS_delete_module) from [<c0009500>] (ret_fast_syscall+0x0/0x2c) r7:00000081 r6:0000009a r5:beb47b9c r4:b6f1c490 BUG: scheduling while atomic: rmmod/1387/0x00000002 Unable to handle kernel paging request at virtual address 00081f84 pgd = c719c000 [00081f84] *pgd=47197831, *pte=00000000, *ppte=00000000 Internal error: Oops: 80000005 [#1] PREEMPT ARM Process rmmod (pid: 1387, stack limit = 0xc78621c0) ---[ end trace 3f34e0dc194f9160 ]--- note: rmmod[1387] exited with preempt_count 1 Segmentation fault
> > regards > Philipp >
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