On Tue, Dec 06, 2016 at 04:18:15AM +0530, Julius Hemanth Pitti wrote:
> Currently iTCO_wdt silently resets the board when timeout
> occurs.
>
> This patch introduces new "panic_on_timeout" module param,
> which when set allows the iTCO_wdt to call panic when
> watchdog timeout occurs, this help to boot to crash
> kernel and collect core dump for further analysis.
>
Not really sure how to handle this. The registers accessed are definitely not
available on all versions of the iTCO watchdog, so it would have to be enabled
on a per chip version basis. Old versions of Intel documents state that bit 9
of TCO1_CNT must not be changed, and list bit 8 as reserved.
Also, doesn't using the NMI/SMI to detect the timeout mean that the watchdog
fires earlier ?
Then there is the question if this would be better handled using the pretimeout
framework.
Guenter
> Cc: xe-kernel@xxxxxxxxxxxxxxxxxx
> Cc: jpitti@xxxxxxxxxx
> Signed-off-by: Julius Hemanth Pitti <jpitti@xxxxxxxxx>
> ---
> drivers/watchdog/iTCO_wdt.c | 61 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 61 insertions(+)
>
> diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c
> index 06fcb6c..23ddcf4 100644
> --- a/drivers/watchdog/iTCO_wdt.c
> +++ b/drivers/watchdog/iTCO_wdt.c
> @@ -66,6 +66,7 @@
> #include <linux/spinlock.h> /* For spin_lock/spin_unlock/... */
> #include <linux/uaccess.h> /* For copy_to_user/put_user/... */
> #include <linux/io.h> /* For inb/outb/... */
> +#include <linux/nmi.h>
> #include <linux/platform_data/itco_wdt.h>
>
> #include "iTCO_vendor.h"
> @@ -76,6 +77,24 @@
> /* SMI Control and Enable Register */
> #define SMI_EN (iTCO_wdt_private.smi_res->start)
>
> +static int panic_on_timeout;
> +module_param(panic_on_timeout, int, 0);
> +MODULE_PARM_DESC(panic_on_timeout,
> + "Panic on NMI instead of Reset (1 = panic), default=0.");
> +
> +/* NMI2SMI_EN is bit 9 of TCO1_CNT register
> + * Read/Write
> + * 0 = Normal NMI functionality.
> + * 1 = Forces all NMIs to instead cause SMIs
> + * This depends on NMI_EN and GBL_SMI_EN bits.
> + */
> +#define NMI2SMI_EN (1 << 9)
> +
> +/* NMI_NOW is bit 8 of TCO1_CNT register.
> + * Read/'Write to Clear'
> + */
> +#define NMI_NOW (1 << 8)
> +
> #define TCO_RLD (TCOBASE + 0x00) /* TCO Timer Reload and Curr. Value */
> #define TCOv1_TMR (TCOBASE + 0x01) /* TCOv1 Timer Initial Value */
> #define TCO_DAT_IN (TCOBASE + 0x02) /* TCO Data In Register */
> @@ -236,6 +255,15 @@ static int iTCO_wdt_start(struct watchdog_device *wd_dev)
> val &= 0xf7ff;
> outw(val, TCO1_CNT);
> val = inw(TCO1_CNT);
> +
> + if (panic_on_timeout) {
> + /* Make sure NMIs are allowed to fire */
> + if (NMI2SMI_EN & val) {
Yoda programming in kernel not desirable is (even more so if used
inconsistently).
> + val &= ~(NMI2SMI_EN);
Unnecessary ( )
> + outw(val, TCO1_CNT);
> + pr_info("NMIs are no longer routed to SMIs\n");
> + }
> + }
> spin_unlock(&iTCO_wdt_private.io_lock);
>
> if (val & 0x0800)
> @@ -422,6 +450,26 @@ static void iTCO_wdt_cleanup(void)
> iTCO_wdt_private.gcs_pmc = NULL;
> }
>
> +/*
> + * iTCO_wdt_timeout_handler: Handler for watchdog timeout NMI event.
> + */
> +int iTCO_wdt_timeout_handler(unsigned int ulReason, struct pt_regs *regs)
> +{
> + unsigned long val32 = inw(TCO1_CNT);
> +
> + if (val32 & NMI_NOW) {
> + /* Clear NMI - Bit 8 within TCO1_CNT is write to clear */
> + outw(val32, TCO1_CNT);
> +
> + /* Crash the system */
> + nmi_panic(regs, "iTCO_wdt: Watchdog timeout");
> +
> + /* Never returns */
> + return NMI_HANDLED;
> + }
> + return NMI_DONE;
> +}
> +
> static int iTCO_wdt_probe(struct platform_device *dev)
> {
> int ret = -ENODEV;
> @@ -552,11 +600,21 @@ static int iTCO_wdt_probe(struct platform_device *dev)
> goto unreg_tco;
> }
>
> + if (panic_on_timeout) {
> + ret = register_nmi_handler(NMI_UNKNOWN, iTCO_wdt_timeout_handler, 0, "iTCO_wdt");
> + if (ret != 0) {
> + pr_err("cannot register NMI Handler for iTCO_wdt watchdog (err=%d)\n", ret);
> + goto unreg_wd;
> + }
> + }
> +
> pr_info("initialized. heartbeat=%d sec (nowayout=%d)\n",
> heartbeat, nowayout);
>
> return 0;
>
> +unreg_wd:
> + watchdog_unregister_device(&iTCO_wdt_watchdog_dev);
> unreg_tco:
> release_region(iTCO_wdt_private.tco_res->start,
> resource_size(iTCO_wdt_private.tco_res));
> @@ -581,6 +639,9 @@ static int iTCO_wdt_probe(struct platform_device *dev)
>
> static int iTCO_wdt_remove(struct platform_device *dev)
> {
> + if (panic_on_timeout)
> + unregister_nmi_handler(NMI_UNKNOWN, "iTCO_wdt");
> +
> if (iTCO_wdt_private.tco_res || iTCO_wdt_private.smi_res)
> iTCO_wdt_cleanup();
>
> --
> 2.10.1
>
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