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SubjectRE: [PATCH 1/2] firmware: imx: SCU irq should ONLY be enabled after SCU IPC is ready
Date
Hi, Guenter

> -----Original Message-----
> From: Guenter Roeck [mailto:groeck7@gmail.com] On Behalf Of Guenter
> Roeck
> Sent: Thursday, April 25, 2019 10:15 AM
> To: Anson Huang <anson.huang@nxp.com>; shawnguo@kernel.org;
> s.hauer@pengutronix.de; kernel@pengutronix.de; festevam@gmail.com;
> wim@linux-watchdog.org; Aisheng Dong <aisheng.dong@nxp.com>; linux-
> arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> watchdog@vger.kernel.org
> Cc: dl-linux-imx <linux-imx@nxp.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.

Thanks,
Anson

>
> Guenter
>
> > Fixes: 851826c7566e ("firmware: imx: enable imx scu general irq
> > function")
> > Signed-off-by: Anson Huang <Anson.Huang@nxp.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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