linux-kernel - RE: [PATCH 1/2] firmware: imx: SCU irq should ONLY be enabled after SCU IPC is ready

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Date:   Thu, 25 Apr 2019 06:51:11 +0000
From:   Anson Huang <anson.huang@....com>
To:     Guenter Roeck <linux@...ck-us.net>,
        "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>
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

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.

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;
> >