Revert "watchdog: iTCO_wdt: Account for rebooting on second timeout"

PATCH In review Guenter Roeck 3 participants 5 messages Oct 8, 2021 – Oct 26, 2021 Watchdog device drivers

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Guenter Roeck

author maintainer

2021-10-08 00:33 UTC #0 lore raw

PATCH 1/1 Revert "watchdog: iTCO_wdt: Account for rebooting on second timeout"

This reverts commit cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout") and commit aec42642d91f ("watchdog: iTCO_wdt:
Fix detection of SMI-off case") since those patches cause a regression on certain boards (https://bugzilla.kernel.org/show_bug.cgi?id=213809).

While this revert may result in some boards to only reset after twice the configured timeout value, that is still better than a watchdog reset after half the configured value.

Fixes cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout")

Fixes aec42642d91f ("watchdog: iTCO_wdt: Fix detection of SMI-off case")

Cc Jan Kiszka <[email protected]>

Cc Mantas Mikulėnas <[email protected]>

Reported-by Javier S. Pedro <[email protected]>

Signed-off-by Guenter Roeck <[email protected]>

---
 drivers/watchdog/iTCO_wdt.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

drivers/watchdog/iTCO_wdt.c +3 -9

index 643c6c2d0b72..ced2fc0deb8c 100644
@@ -71,8 +71,6 @@
 #define TCOBASE(p)	((p)->tco_res->start)
 /* SMI Control and Enable Register */
 #define SMI_EN(p)	((p)->smi_res->start)
-#define TCO_EN		(1 << 13)
-#define GBL_SMI_EN	(1 << 0)
 
 #define TCO_RLD(p)	(TCOBASE(p) + 0x00) /* TCO Timer Reload/Curr. Value */
 #define TCOv1_TMR(p)	(TCOBASE(p) + 0x01) /* TCOv1 Timer Initial Value*/

@@ -357,12 +355,8 @@ static int iTCO_wdt_set_timeout(struct watchdog_device *wd_dev, unsigned int t)
 
 	tmrval = seconds_to_ticks(p, t);
 
-	/*
-	 * If TCO SMIs are off, the timer counts down twice before rebooting.
-	 * Otherwise, the BIOS generally reboots when the SMI triggers.
-	 */
-	if (p->smi_res &&
-	    (inl(SMI_EN(p)) & (TCO_EN | GBL_SMI_EN)) != (TCO_EN | GBL_SMI_EN))
+	/* For TCO v1 the timer counts down twice before rebooting */
+	if (p->iTCO_version == 1)
 		tmrval /= 2;
 
 	/* from the specs: */

@@ -527,7 +521,7 @@ static int iTCO_wdt_probe(struct platform_device *pdev)
 		 * Disables TCO logic generating an SMI#
 		 */
 		val32 = inl(SMI_EN(p));
-		val32 &= ~TCO_EN;	/* Turn off SMI clearing watchdog */
+		val32 &= 0xffffdfff;	/* Turn off SMI clearing watchdog */
 		outl(val32, SMI_EN(p));
 	}

Signature · 1 line

2.33.0

Jan Kiszka

2021-10-08 07:52 UTC #1 lore raw

Quoted 49 lines · Guenter Roeck

This reverts commit cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout") and commit aec42642d91f ("watchdog: iTCO_wdt:
Fix detection of SMI-off case") since those patches cause a regression on certain boards (https://bugzilla.kernel.org/show_bug.cgi?id=213809).
While this revert may result in some boards to only reset after twice the configured timeout value, that is still better than a watchdog reset after half the configured value.
Fixes cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout")
Fixes aec42642d91f ("watchdog: iTCO_wdt: Fix detection of SMI-off case")
Cc Jan Kiszka <[email protected]>
Cc Mantas Mikulėnas <[email protected]>
Reported-by Javier S. Pedro <[email protected]>
Signed-off-by Guenter Roeck <[email protected]>
---
 drivers/watchdog/iTCO_wdt.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)
drivers/watchdog/iTCO_wdt.c +2 -8
index 643c6c2d0b72..ced2fc0deb8c 100644
@@ -71,8 +71,6 @@
 #define TCOBASE(p)	((p)->tco_res->start)
 /* SMI Control and Enable Register */
 #define SMI_EN(p)	((p)->smi_res->start)
-#define TCO_EN		(1 << 13)
-#define GBL_SMI_EN	(1 << 0)
 
 #define TCO_RLD(p)	(TCOBASE(p) + 0x00) /* TCO Timer Reload/Curr. Value */
 #define TCOv1_TMR(p)	(TCOBASE(p) + 0x01) /* TCOv1 Timer Initial Value*/
@@ -357,12 +355,8 @@ static int iTCO_wdt_set_timeout(struct watchdog_device *wd_dev, unsigned int t)
 
 	tmrval = seconds_to_ticks(p, t);
 
-	/*
-	 * If TCO SMIs are off, the timer counts down twice before rebooting.
-	 * Otherwise, the BIOS generally reboots when the SMI triggers.
-	 */
-	if (p->smi_res &&
-	    (inl(SMI_EN(p)) & (TCO_EN | GBL_SMI_EN)) != (TCO_EN | GBL_SMI_EN))
+	/* For TCO v1 the timer counts down twice before rebooting */
+	if (p->iTCO_version == 1)
 		tmrval /= 2;
 
 	/* from the specs: */

drivers/watchdog/iTCO_wdt.c static int iTCO_wdt_probe(struct platform_device *pdev) · line 527

Quoted 8 lines

drivers/watchdog/iTCO_wdt.c +1 -1

@@ -527,7 +521,7 @@ static int iTCO_wdt_probe(struct platform_device *pdev)
 		 * Disables TCO logic generating an SMI#
 		 */
 		val32 = inl(SMI_EN(p));
-		val32 &= ~TCO_EN;	/* Turn off SMI clearing watchdog */
+		val32 &= 0xffffdfff;	/* Turn off SMI clearing watchdog */
 		outl(val32, SMI_EN(p));
 	}

Sigh, how broken is this architecture of the iTCO? Agreed, this leaves no option then.

BTW, the fact that we saw an inconsistency in read-back timeout indicates that there is still an issue for the remaining /= 2 case (means v1), but I'm loosing interest in fixing those issues, given how hard it is to test broadly without breaking users first.

Jan

Signature · 2 lines

Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux

Guenter Roeck

author maintainer

2021-10-08 13:05 UTC #2 lore raw

Quoted 62 lines · Jan Kiszka

Quoted 49 lines · Guenter Roeck
This reverts commit cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout") and commit aec42642d91f ("watchdog: iTCO_wdt:
Fix detection of SMI-off case") since those patches cause a regression on certain boards (https://bugzilla.kernel.org/show_bug.cgi?id=213809).
While this revert may result in some boards to only reset after twice the configured timeout value, that is still better than a watchdog reset after half the configured value.
Fixes cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout")
Fixes aec42642d91f ("watchdog: iTCO_wdt: Fix detection of SMI-off case")
Cc Jan Kiszka <[email protected]>
Cc Mantas Mikulėnas <[email protected]>
Reported-by Javier S. Pedro <[email protected]>
Signed-off-by Guenter Roeck <[email protected]>
---
  drivers/watchdog/iTCO_wdt.c | 12 +++---------
  1 file changed, 3 insertions(+), 9 deletions(-)
drivers/watchdog/iTCO_wdt.c +2 -8
index 643c6c2d0b72..ced2fc0deb8c 100644
@@ -71,8 +71,6 @@
  #define TCOBASE(p)	((p)->tco_res->start)
  /* SMI Control and Enable Register */
  #define SMI_EN(p)	((p)->smi_res->start)
-#define TCO_EN		(1 << 13)
-#define GBL_SMI_EN	(1 << 0)
 
  #define TCO_RLD(p)	(TCOBASE(p) + 0x00) /* TCO Timer Reload/Curr. Value */
  #define TCOv1_TMR(p)	(TCOBASE(p) + 0x01) /* TCOv1 Timer Initial Value*/
@@ -357,12 +355,8 @@ static int iTCO_wdt_set_timeout(struct watchdog_device *wd_dev, unsigned int t)
 
  	tmrval = seconds_to_ticks(p, t);
 
-	/*
-	 * If TCO SMIs are off, the timer counts down twice before rebooting.
-	 * Otherwise, the BIOS generally reboots when the SMI triggers.
-	 */
-	if (p->smi_res &&
-	    (inl(SMI_EN(p)) & (TCO_EN | GBL_SMI_EN)) != (TCO_EN | GBL_SMI_EN))
+	/* For TCO v1 the timer counts down twice before rebooting */
+	if (p->iTCO_version == 1)
  		tmrval /= 2;
 
  	/* from the specs: */
drivers/watchdog/iTCO_wdt.c static int iTCO_wdt_probe(struct platform_device *pdev) · line 527
Quoted 8 lines
drivers/watchdog/iTCO_wdt.c +1 -1
@@ -527,7 +521,7 @@ static int iTCO_wdt_probe(struct platform_device *pdev)
  		 * Disables TCO logic generating an SMI#
  		 */
  		val32 = inl(SMI_EN(p));
-		val32 &= ~TCO_EN;	/* Turn off SMI clearing watchdog */
+		val32 &= 0xffffdfff;	/* Turn off SMI clearing watchdog */
  		outl(val32, SMI_EN(p));
  	}
 
Sigh, how broken is this architecture of the iTCO? Agreed, this leaves no option then.

Quoted 5 lines

BTW, the fact that we saw an inconsistency in read-back timeout indicates that there is still an issue for the remaining /= 2 case (means v1), but I'm loosing interest in fixing those issues, given how hard it is to test broadly without breaking users first.

Agreed. This is because the /=2 handling is only implemented in iTCO_wdt_set_timeout() without matching code in iTCO_wdt_get_timeleft(). I don't have hardware to test, so I am not going to touch that code myself. We can address that if/when someone reports the actual problem and has the ability to test a fix.

Thanks,
Guenter

Guenter Roeck

author maintainer

2021-10-20 19:44 UTC #3 lore raw

In reply to Guenter Roeck

Wim,

Quoted 9 lines · Guenter Roeck

This reverts commit cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout") and commit aec42642d91f ("watchdog: iTCO_wdt:
Fix detection of SMI-off case") since those patches cause a regression on certain boards (https://bugzilla.kernel.org/show_bug.cgi?id=213809).
While this revert may result in some boards to only reset after twice the configured timeout value, that is still better than a watchdog reset after half the configured value.

Quoted 6 lines

Fixes cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout")
Fixes aec42642d91f ("watchdog: iTCO_wdt: Fix detection of SMI-off case")
Cc Jan Kiszka <[email protected]>
Cc Mantas Mikulėnas <[email protected]>
Reported-by Javier S. Pedro <[email protected]>
Signed-off-by Guenter Roeck <[email protected]>

Any chance you can send a pull request with this patch prior to the v5.15 release ?

Thanks,
Guenter

Wim Van Sebroeck

2021-10-26 15:46 UTC #4 lore raw

Hi Guenter,

Quoted 17 lines · Guenter Roeck

Quoted 9 lines
This reverts commit cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout") and commit aec42642d91f ("watchdog: iTCO_wdt:
Fix detection of SMI-off case") since those patches cause a regression on certain boards (https://bugzilla.kernel.org/show_bug.cgi?id=213809).
While this revert may result in some boards to only reset after twice the configured timeout value, that is still better than a watchdog reset after half the configured value.
Quoted 6 lines
Fixes cb011044e34c ("watchdog: iTCO_wdt: Account for rebooting on second timeout")
Fixes aec42642d91f ("watchdog: iTCO_wdt: Fix detection of SMI-off case")
Cc Jan Kiszka <[email protected]>
Cc Mantas Mikulėnas <[email protected]>
Reported-by Javier S. Pedro <[email protected]>
Signed-off-by Guenter Roeck <[email protected]>

Quoted 2 lines

Any chance you can send a pull request with this patch prior to the v5.15 release ?

Will do it this evening.

Kind regards,
Wim.