RE: [PATCH] clk: imx: imx8mp: Add delay after power up

From: Peng Fan
Date: Mon Apr 29 2024 - 21:45:04 EST

> Subject: Re: [PATCH] clk: imx: imx8mp: Add delay after power up
>
> On Fri, Apr 26, 2024 at 05:40:52PM +0800, Shengjiu Wang wrote:
> > On Fri, Apr 26, 2024 at 4:49 AM Frank Li <Frank.li@xxxxxxx> wrote:
> > >
> > > On Thu, Apr 25, 2024 at 06:19:24PM +0800, Shengjiu Wang wrote:
> > > > According to comments in drivers/pmdomain/imx/gpcv2.c:
> > > >
> > > > /* request the ADB400 to power up */
> > > > if (domain->bits.hskreq) {
> > > > regmap_update_bits(domain->regmap, domain->regs->hsk,
> > > > domain->bits.hskreq,
> > > > domain->bits.hskreq);
> > > >
> > > > /*
> > > > * ret = regmap_read_poll_timeout(domain->regmap, domain-
> >regs->hsk, reg_val,
> > > > * (reg_val & domain->bits.hskack), 0,
> > > > * USEC_PER_MSEC);
> > > > * Technically we need the commented code to wait handshake.
> But that needs
> > > > * the BLK-CTL module BUS clk-en bit being set.
> > > > *
> > > > * There is a separate BLK-CTL module and we will have such a
> driver for it,
> > > > * that driver will set the BUS clk-en bit and handshake will be
> triggered
> > > > * automatically there. Just add a delay and suppose the
> handshake finish
> > > > * after that.
> > > > */
> > > > }
> > > >
> > > > The BLK-CTL module needs to add delay to wait for a handshake
> > > > request finished before accessing registers, which is just after the
> enabling of power domain.
> > > >
> > > > Otherwise there is error:
> > > >
> > > > [ 2.180834] SError Interrupt on CPU1, code 0x00000000bf000002 --
> SError
> > > > [ 2.180849] CPU: 1 PID: 48 Comm: kworker/u16:2 Not tainted 6.9.0-
> rc5-next-20240424-00003-g21cec88845c6 #171
> > > > [ 2.180856] Hardware name: NXP i.MX8MPlus EVK board (DT)
> > > > [ 2.180861] Workqueue: events_unbound deferred_probe_work_func
> > > > [ 2.180878] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS
> BTYPE=--)
> > > > [ 2.180885] pc : clk_imx8mp_audiomix_runtime_resume+0x34/0x44
> > > > [ 2.180900] lr : pm_generic_runtime_resume+0x2c/0x44
> > > > [ 2.180910] sp : ffff800083423a20
> > > > [ 2.180913] x29: ffff800083423a20 x28: 0000000000000000 x27:
> 0000000000000000
> > > > [ 2.180922] x26: ffff0000c0e4e410 x25: 0000000000000000 x24:
> 0000000000000000
> > > > [ 2.180935] x23: 0000000000000000 x22: ffff0000c02afd20 x21:
> 0000000000000000
> > > > [ 2.180945] x20: ffff0000c162a000 x19: ffff0000c0e52810 x18:
> ffffffffffffffff
> > > > [ 2.180959] x17: 0000000000000000 x16: 0000000000000100 x15:
> ffff8000834239f0
> > > > [ 2.180970] x14: ffff0000c03d0a1c x13: ffff0000c0a03440 x12:
> 00000000000003c7
> > > > [ 2.180982] x11: 0000000000000000 x10: ffff8000825010ba x9 :
> 0000000000000008
> > > > [ 2.180993] x8 : 0000000000000008 x7 : 0000000000000000 x6 :
> 0000000000000000
> > > > [ 2.181005] x5 : ffff8000838b0000 x4 : ffff0000c0e66088 x3 :
> ffff8000813852c0
> > > > [ 2.181018] x2 : 0000000000000000 x1 : 0000000000000004 x0 :
> ffff8000838b0300
> > > > [ 2.181035] Kernel panic - not syncing: Asynchronous SError Interrupt
> > > > [ 2.181038] CPU: 1 PID: 48 Comm: kworker/u16:2 Not tainted 6.9.0-
> rc5-next-20240424-00003-g21cec88845c6 #171
> > > > [ 2.181047] Hardware name: NXP i.MX8MPlus EVK board (DT)
> > > > [ 2.181050] Workqueue: events_unbound deferred_probe_work_func
> > > > [ 2.181064] Call trace:
> > > > [ 2.181066] dump_backtrace+0x90/0xe8
> > > > [ 2.181080] show_stack+0x18/0x24
> > > > [ 2.181091] dump_stack_lvl+0x34/0x8c
> > > > [ 2.181104] dump_stack+0x18/0x24
> > > > [ 2.181117] panic+0x39c/0x3d0
> > > > [ 2.181129] nmi_panic+0x48/0x94
> > > > [ 2.181142] arm64_serror_panic+0x6c/0x78
> > > > [ 2.181149] do_serror+0x3c/0x70
> > > > [ 2.181157] el1h_64_error_handler+0x30/0x48
> > > > [ 2.181164] el1h_64_error+0x64/0x68
> > > > [ 2.181171] clk_imx8mp_audiomix_runtime_resume+0x34/0x44
> > > > [ 2.181183] __genpd_runtime_resume+0x30/0x80
> > > > [ 2.181195] genpd_runtime_resume+0x110/0x244
> > > > [ 2.181205] __rpm_callback+0x48/0x1d8
> > > > [ 2.181213] rpm_callback+0x68/0x74
> > > > [ 2.181224] rpm_resume+0x468/0x6c0
> > > > [ 2.181234] __pm_runtime_resume+0x50/0x94
> > > > [ 2.181243] pm_runtime_get_suppliers+0x60/0x8c
> > > > [ 2.181258] __driver_probe_device+0x48/0x12c
> > > > [ 2.181268] driver_probe_device+0xd8/0x15c
> > > > [ 2.181278] __device_attach_driver+0xb8/0x134
> > > > [ 2.181290] bus_for_each_drv+0x84/0xe0
> > > > [ 2.181302] __device_attach+0x9c/0x188
> > > > [ 2.181312] device_initial_probe+0x14/0x20
> > > > [ 2.181323] bus_probe_device+0xac/0xb0
> > > > [ 2.181334] deferred_probe_work_func+0x88/0xc0
> > > > [ 2.181344] process_one_work+0x150/0x290
> > > > [ 2.181357] worker_thread+0x2f8/0x408
> > > > [ 2.181370] kthread+0x110/0x114
> > > > [ 2.181381] ret_from_fork+0x10/0x20
> > > > [ 2.181391] SMP: stopping secondary CPUs
> > > > [ 2.181400] Kernel Offset: disabled
> > > > [ 2.181403] CPU features: 0x0,00000040,00100000,4200421b
> > > > [ 2.181407] Memory Limit: none
> > > > [ 2.463040] ---[ end Kernel panic - not syncing: Asynchronous SError
> Interrupt ]---
> > > >
> > > > Fixes: 1496dd413b2e ("clk: imx: imx8mp: Add pm_runtime support for
> > > > power saving")
> > > > Reported-by: Francesco Dolcini <francesco@xxxxxxxxxx>
> > > > Signed-off-by: Shengjiu Wang <shengjiu.wang@xxxxxxx>
> > > > ---
> > > > drivers/clk/imx/clk-imx8mp-audiomix.c | 7 +++++++
> > > > 1 file changed, 7 insertions(+)
> > > >
> > > > diff --git a/drivers/clk/imx/clk-imx8mp-audiomix.c
> > > > b/drivers/clk/imx/clk-imx8mp-audiomix.c
> > > > index e4231e9c8f05..cb44c460548e 100644
> > > > --- a/drivers/clk/imx/clk-imx8mp-audiomix.c
> > > > +++ b/drivers/clk/imx/clk-imx8mp-audiomix.c
> > > > @@ -6,6 +6,7 @@
> > > > */
> > > >
> > > > #include <linux/clk-provider.h>
> > > > +#include <linux/delay.h>
> > > > #include <linux/device.h>
> > > > #include <linux/io.h>
> > > > #include <linux/mod_devicetable.h> @@ -362,6 +363,12 @@ static
> > > > int clk_imx8mp_audiomix_runtime_suspend(struct device *dev)
> > > >
> > > > static int clk_imx8mp_audiomix_runtime_resume(struct device *dev)
> > > > {
> > > > + /*
> > > > + * According to the drivers/pmdomain/imx/gpcv2.c
> > > > + * need to wait for handshake request to propagate
> > > > + */
> > > > + udelay(5);
> > > > +
> > >
> > > https://lore.kernel.org/imx/20230727152503.2199550-1-
> shenwei.wang@nx
> > > p.com/T/#m2dc5111e9628235f031c0bad2a137222b0205a61
> > >
> > > supposed clk_imx8mp_audiomix_save_restore() is that write save data
> > > into some registers.
> > >
> > > See above link for detail, it may not delay 5us before write to register.
> > > You need
> > > readl();
> > > udelay(5);
> > > writel();
> >
> > Here we need to wait for the handshake to be ready, we have nothing
> > to be read.
>
> It should power_on by writel() at somewhere, maybe gpcv2.c.
> 1. writel() //power on
>
> 2. udelay(5) // in your code,
>
> 3. writel() // in your driver to init audiomix controller.
>
> 1,2,3 just distribute at difference file, but basic work flow should be the same.
>
> If here nothing to read, you put udelay at power_on code, maybe gpcv2.

No. Because BLK CTRL enable BUS_EN, before enable BUS_EN, udelay does
not help. For the audiomix, move to gpcv2 would work, but gpcv2 is
not only for i.MX8MP audiomix. For mixes, default not enable BUS_EN
after power on, the udelay must be in blk ctrl driver.

>
> Other driver may meet similar problem, you met this problem just this driver
> running close to gpc's v2 by driver probe order or compiler linker driver order.
>
> >
> > but I don't really understand why the code is commented.
> >
> > /*
> > * ret = regmap_read_poll_timeout(domain->regmap,
> > domain->regs->hsk, reg_val,
> > * (reg_val &
> > domain->bits.hskack), 0,
> > * USEC_PER_MSEC);
> >
> > If we uncomment the code, it can also fix the issue.
>
> dose git blame give some clue or ask original driver owner?

For BLK CTRL whose reset value not 1 for BUS_EN, the wait will always timeout.

Regards,
Peng.
>
> >
> > best regards
> > Shengjiu Wang
> >
> > >
> > > > clk_imx8mp_audiomix_save_restore(dev, false);
> > > >
> > > > return 0;
> > > > --
> > > > 2.34.1
> > > >