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Message-ID: <42d578c52a590f50f90e2378ef3e2a1522038fc2.camel@siemens.com>
Date: Wed, 12 Jul 2023 06:05:35 +0000
From: "Li, Hua Qian" <HuaQian.Li@...mens.com>
To: "linux@...ck-us.net" <linux@...ck-us.net>,
"wim@...ux-watchdog.org" <wim@...ux-watchdog.org>,
"conor+dt@...nel.org" <conor+dt@...nel.org>,
"krzysztof.kozlowski+dt@...aro.org"
<krzysztof.kozlowski+dt@...aro.org>,
"robh+dt@...nel.org" <robh+dt@...nel.org>
CC: "Su, Bao Cheng" <baocheng.su@...mens.com>,
"kristo@...nel.org" <kristo@...nel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"huaqianlee@...il.com" <huaqianlee@...il.com>,
"nm@...com" <nm@...com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"Kiszka, Jan" <jan.kiszka@...mens.com>,
"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
"vigneshr@...com" <vigneshr@...com>
Subject: Re: [PATCH v2 3/3] watchdog:rit_wdt: Add support for WDIOF_CARDRESET
On Tue, 2023-07-11 at 22:01 -0700, Guenter Roeck wrote:
> On 7/11/23 21:03, Li, Hua Qian wrote:
> > On Tue, 2023-07-11 at 19:32 -0700, Guenter Roeck wrote:
> > > On 7/11/23 02:17, huaqian.li@...mens.com wrote:
> > > > From: Li Hua Qian <huaqian.li@...mens.com>
> > > >
> > > > This patch adds the WDIOF_CARDRESET support for the platform
> > > > watchdog
> > > > whose hardware does not support this feature, to know if the
> > > > board
> > > > reboot is due to a watchdog reset.
> > > >
> > > > This is done via reserved memory(RAM), which indicates if
> > > > specific
> > > > info saved, triggering the watchdog reset in last boot.
> > > >
> > > > Signed-off-by: Li Hua Qian <huaqian.li@...mens.com>
> > > > ---
> > > > drivers/watchdog/rti_wdt.c | 48
> > > > ++++++++++++++++++++++++++++++++++++++
> > > > 1 file changed, 48 insertions(+)
> > > >
> > > > diff --git a/drivers/watchdog/rti_wdt.c
> > > > b/drivers/watchdog/rti_wdt.c
> > > > index ce8f18e93aa9..77fd6b54137c 100644
> > > > --- a/drivers/watchdog/rti_wdt.c
> > > > +++ b/drivers/watchdog/rti_wdt.c
> > > > @@ -18,6 +18,7 @@
> > > > #include <linux/pm_runtime.h>
> > > > #include <linux/types.h>
> > > > #include <linux/watchdog.h>
> > > > +#include <linux/of.h>
> > > >
> > > > #define DEFAULT_HEARTBEAT 60
> > > >
> > > > @@ -52,6 +53,11 @@
> > > >
> > > > #define DWDST BIT(1)
> > > >
> > > > +#define PON_REASON_SOF_NUM 0xBBBBCCCC
> > > > +#define PON_REASON_MAGIC_NUM 0xDDDDDDDD
> > > > +#define PON_REASON_EOF_NUM 0xCCCCBBBB
> > > > +#define PON_REASON_ITEM_BITS 0xFFFFFFFF
> > > > +
> > > > static int heartbeat = DEFAULT_HEARTBEAT;
> > > >
> > > > /*
> > > > @@ -198,6 +204,11 @@ static int rti_wdt_probe(struct
> > > > platform_device *pdev)
> > > > struct rti_wdt_device *wdt;
> > > > struct clk *clk;
> > > > u32 last_ping = 0;
> > > > + u32 reserved_mem_size;
> > > > + unsigned long *vaddr;
> > > > + unsigned long paddr;
> > > > + u32 data[3];
> > > > + u32 reg[8];
> > > >
> > > > wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> > > > if (!wdt)
> > > > @@ -284,6 +295,43 @@ static int rti_wdt_probe(struct
> > > > platform_device *pdev)
> > > > }
> > > > }
> > > >
> > > > + ret = of_property_read_variable_u32_array(pdev-
> > > > > dev.of_node, "reg", reg,
> > > > + 0, ARRAY_SIZE(reg));
> > > > + if (ret < 0) {
> > > > + dev_err(dev, "cannot read the reg info.\n");
> > > > + goto err_iomap;
> > > > + }
> > >
> > > This aborts if the property does not exist, which is
> > > unacceptable.
> > > Any such addition must be optional.
> > Agree, refactor it.
> > >
> > > > +
> > > > + /*
> > > > + * If reserved memory is defined for watchdog reset
> > > > cause.
> > > > + * Readout the Power-on(PON) reason and pass to
> > > > bootstatus.
> > > > + */
> > > > + if (ret == 8) {
> > > > + paddr = reg[5];
> > > > + reserved_mem_size = reg[7];
> > >
> > > It seems odd that reserved_mem_size is not checked,
> > ACK
> > > and that it is even provided
> > > given that it needs to be (at least) 24 bytes, and any other
> > > value
> > > does not really
> > > make sense.
> > >
> > I was thinkg to add the reliability, but it seems to be unnecessary
> > and
> > pointless. Were you suggesting that 8 bytes are enough?
> >
>
> No.
I guess I misunderstood you. Here you was suggesting that
reserved_mem_size should be checked and make sure the value to be at
least 24 bytes. Am I understanding you correctly?
> > > > MEMREMAP_WB);
> > > > + if (vaddr == NULL) {
> > > > + dev_err(dev, "Failed to map memory-
> > > > region.\n");
> > > > + goto err_iomap;
> > >
> > > This returns 8, which would be an odd error return.
> > >
> > ACK,refactor it.
> > > > + }
> > > > +
> > > > + data[0] = *vaddr & PON_REASON_ITEM_BITS;
> > > > + data[1] = *(vaddr + 1) & PON_REASON_ITEM_BITS;
> > > > + data[2] = *(vaddr + 2) & PON_REASON_ITEM_BITS;
> > > > +
> > >
> > > The & seems pointless / wasteful. Why ignore the upper 32 bits of
> > > each location ?
> > > Either make it u32 or make it u64 and use the entire 64 bit.
> > > Besides,
> > > vaddr[0..2] would make the code much easier to read.
> > >
> > ACK, refactor it.
> > > > + dev_dbg(dev, "Watchdog: sof = %lX, data = %lX,
> > > > eof
> > > > = %lX\n",
> > > > + data[0], data[1], data[2]);
> > > > +
> > > > + if ((data[0] == PON_REASON_SOF_NUM)
> > > > + && (data[1] == PON_REASON_MAGIC_NUM)
> > > > + && (data[1] == PON_REASON_MAGIC_NUM)) {
> > >
> > > Unnecessary inner (), and I don't see the point of checking
> > > data[1]
> > > twice.
> > Yeah, a typo happened.
> > >
> > > > + dev_info(dev, "Watchdog reset cause
> > > > detected.\n");
> > >
> > > Unnecessary noise.
> > ACK,rename dev_info to dev_dbg.
> > >
> > > > + wdd->bootstatus |= WDIOF_CARDRESET;
> > > > + }
> > > > + memset(vaddr, 0, reserved_mem_size);
> > > > + memunmap(vaddr);
> > > > + }
> > >
> > > And some random data in the property is acceptable ? That is odd,
> > > especially
> > > after mandating the property itself.
> > >
> > Yeah, do you have any suggestions about how to store the watchdog
> > reset cause?
> >
>
> No, and that is not the point I was trying to make. Your code
> actively
> aborts probe if the "reg" property does not exist at all, but then it
> silently ignores if it contains a random number of elements (other
> than 8). For example, something like
> reg = <0x1234 0x5678>
> is silently ignored. If anything, _that_ should return -EINVAL
> because it is obviously wrong.
Now I get it, many thanks for pointing out.
>
> On a higher level, the entire code puzzles me. Obviously there
> must be a means for the BIOS or ROMMON to write PON_REASON_SOF_NUM
> into some memory area. That means the BIOS/ROMMON must be able
> to detect that situation. Why not use the same code to detect this
> in the driver without the complexity of passing it from BIOS/ROMMON
> to driver in some random memory area ?
>
In TI AM65x cases, the hardware is not capable of issuing a reset on
its own, and is not possible to record or detect the watchdog reset
situation. So `k3-rit-wdt` firmware which runs in a mcu core was used
to detect the watchdog interrupt and reset the Soc. Here I am trying to
write the reason in this firmware when watchdog interrupt happens, and
read it out in kernel.
> > Best regards,
> > Li Hua Qian
> > > > +
> > > > watchdog_init_timeout(wdd, heartbeat, dev);
> > > >
> > > > ret = watchdog_register_device(wdd);
> > >
> >
>
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