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Message-ID: <20190426201421.GA21075@roeck-us.net>
Date: Fri, 26 Apr 2019 13:14:21 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Anson Huang <anson.huang@....com>
Cc: "shawnguo@...nel.org" <shawnguo@...nel.org>,
"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
"kernel@...gutronix.de" <kernel@...gutronix.de>,
"festevam@...il.com" <festevam@...il.com>,
"wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
Aisheng Dong <aisheng.dong@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 1/2] firmware: imx: SCU irq should ONLY be enabled after
SCU IPC is ready
On Thu, Apr 25, 2019 at 06:51:11AM +0000, Anson Huang wrote:
> Hi, Guenter
>
> > -----Original Message-----
> > From: Guenter Roeck [mailto:groeck7@...il.com] On Behalf Of Guenter
> > Roeck
> > Sent: Thursday, April 25, 2019 10:15 AM
> > To: Anson Huang <anson.huang@....com>; shawnguo@...nel.org;
> > s.hauer@...gutronix.de; kernel@...gutronix.de; festevam@...il.com;
> > wim@...ux-watchdog.org; Aisheng Dong <aisheng.dong@....com>; linux-
> > arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; linux-
> > watchdog@...r.kernel.org
> > Cc: dl-linux-imx <linux-imx@....com>
> > Subject: Re: [PATCH 1/2] firmware: imx: SCU irq should ONLY be enabled
> > after SCU IPC is ready
> >
> > On 4/24/19 6:14 PM, Anson Huang wrote:
> > > The imx_scu_irq_group_enable() is normally called during module driver
> > > probe phase to enable SCU group irq, e.g., i.MX system controller
> > > watchdog driver will call it during its driver probe phase, as i.MX
> > > system controller watchdog driver does NOT need SCU IPC handle for
> > > operations, so it could be probed before i.MX SCU IPC is ready, and
> > > below dump will show out:
> > >
> > > [ 0.933001] Hardware name: Freescale i.MX8QXP MEK (DT)
> > > [ 0.938129] pstate: 60000005 (nZCv daif -PAN -UAO)
> > > [ 0.942907] pc : imx_scu_call_rpc+0x114/0x158
> > > [ 0.947251] lr : imx_scu_irq_group_enable+0x74/0xc4
> > > [ 0.952113] sp : ffff00001005bae0
> > > [ 0.955415] x29: ffff00001005bae0 x28: ffff0000111bb0a0
> > > [ 0.960712] x27: ffff00001140b000 x26: ffff00001111068c
> > > [ 0.966011] x25: ffff0000111bb100 x24: 0000000000000000
> > > [ 0.971311] x23: ffff0000113d9cd8 x22: 0000000000000001
> > > [ 0.976610] x21: 0000000000000001 x20: ffff80083b51a410
> > > [ 0.981909] x19: ffff000011259000 x18: 0000000000000480
> > > [ 0.987209] x17: 000000000023ffb8 x16: 0000000000000010
> > > [ 0.992508] x15: 000000000000023f x14: ffffffffffffffff
> > > [ 0.997807] x13: 0000000000000018 x12: 0000000000000030
> > > [ 1.003107] x11: 0000000000000003 x10: 0101010101010101
> > > [ 1.008406] x9 : ffffffffffffffff x8 : 7f7f7f7f7f7f7f7f
> > > [ 1.013706] x7 : fefefeff646c606d x6 : 0000000000000000
> > > [ 1.019005] x5 : ffff0000112596c8 x4 : 0000000000000008
> > > [ 1.024304] x3 : 0000000000000003 x2 : 0000000000000001
> > > [ 1.029604] x1 : ffff00001005bb58 x0 : 0000000000000000
> > > [ 1.034905] Call trace:
> > > [ 1.037341] imx_scu_call_rpc+0x114/0x158
> > > [ 1.041334] imx_scu_irq_group_enable+0x74/0xc4
> > > [ 1.045856] imx_sc_wdt_probe+0x24/0x150
> > > [ 1.049766] platform_drv_probe+0x4c/0xb0
> > > [ 1.053762] really_probe+0x1f8/0x2c8
> > > [ 1.057407] driver_probe_device+0x58/0xfc
> > > [ 1.061490] device_driver_attach+0x68/0x70
> > > [ 1.065660] __driver_attach+0x94/0xdc
> > > [ 1.069397] bus_for_each_dev+0x64/0xc0
> > > [ 1.073220] driver_attach+0x20/0x28
> > > [ 1.076782] bus_add_driver+0x148/0x1fc
> > > [ 1.080601] driver_register+0x68/0x120
> > > [ 1.084424] __platform_driver_register+0x4c/0x54
> > > [ 1.089120] imx_sc_wdt_driver_init+0x18/0x20
> > > [ 1.093463] do_one_initcall+0x58/0x1b8
> > > [ 1.097287] kernel_init_freeable+0x1cc/0x288
> > > [ 1.101630] kernel_init+0x10/0x100
> > > [ 1.105101] ret_from_fork+0x10/0x18
> > > [ 1.108669] ---[ end trace 9e03302114457de9 ]---
> > > [ 1.113296] enable irq failed, group 1, mask 1, ret -22
> > >
> > > To avoid such scenario, return -EPROBE_DEFER in
> > > imx_scu_irq_group_enable() API if SCU IPC is NOT ready, then module
> > > driver which calls this API in probe phase will defer probe after SCU IPC
> > ready.
> > >
> > Difficult to comment - I seem to have missed the patch introducing the call to
> > imx_scu_irq_group_enable() from the watchdog driver, and I don't see it in -
> > next either.
> >
> > However, as far as I can see, imx_sc_irq_ipc_handle is initialized from
> > imx_scu_probe(). If the watchdog driver depends on it, it should be a sub-
> > node of fsl,imx-scu, and be instantiated from the call to
> > devm_of_platform_populate() in imx_scu_probe(). This should make the
> > EPROBE_DEFER unnecessary.
> >
> > In other words, the above statement "i.MX system controller watchdog
> > driver does NOT need SCU IPC handle for operations" is no longer accurate.
> > If it needs the interrupt, and the interrupt needs the IPC handle, the
> > watchdog driver does require the IPC handle. It would otherwise not need to
> > defer its probe function until the IPC handle is available.
> >
> > I would like to add that it is highly unusual for a watchdog driver to depend
> > on a firmware driver. However, again, that is difficult to argue since I seem to
> > have missed the patch series introducing that dependency.
>
> I agreed watchdog should be a sub-node of SCU if it depends ON it, but as this API is
> exposed, I think adding such check is necessary, we do NOT know when this API could
> be called, so this protection should be necessary, it is just because I met this issue
> during adding pretimeout function of i.MX SC wdog, so I put the patches together.
>
I agree that the check is necessary for imx_scu_irq_group_enable().
But the watchdog driver should still only be instantiated after
(or, rather, from) its parent driver since that is now the well
defined initialization order.
Guenter
> Thanks,
> Anson
>
> >
> > Guenter
> >
> > > Fixes: 851826c7566e ("firmware: imx: enable imx scu general irq
> > > function")
> > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > > ---
> > > drivers/firmware/imx/imx-scu-irq.c | 3 +++
> > > 1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/firmware/imx/imx-scu-irq.c
> > > b/drivers/firmware/imx/imx-scu-irq.c
> > > index 043833a..687121f 100644
> > > --- a/drivers/firmware/imx/imx-scu-irq.c
> > > +++ b/drivers/firmware/imx/imx-scu-irq.c
> > > @@ -100,6 +100,9 @@ int imx_scu_irq_group_enable(u8 group, u32 mask,
> > u8 enable)
> > > struct imx_sc_rpc_msg *hdr = &msg.hdr;
> > > int ret;
> > >
> > > + if (!imx_sc_irq_ipc_handle)
> > > + return -EPROBE_DEFER;
> > > +
> > > hdr->ver = IMX_SC_RPC_VERSION;
> > > hdr->svc = IMX_SC_RPC_SVC_IRQ;
> > > hdr->func = IMX_SC_IRQ_FUNC_ENABLE;
> > >
>
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