linux-kernel - [PATCH v3] clocksource/fsl: Fix errata A-007728 for flextimer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <1474517563-17706-1-git-send-email-meng.yi@nxp.com>
Date:   Thu, 22 Sep 2016 12:12:43 +0800
From:   Meng Yi <meng.yi@....com>
To:     <daniel.lezcano@...aro.org>, <tglx@...utronix.de>,
        <alexander.stein@...tec-electronic.com>
CC:     <linux-kernel@...r.kernel.org>, Meng Yi <meng.yi@....com>
Subject: [PATCH v3] clocksource/fsl: Fix errata A-007728 for flextimer

If the FTM counter reaches the FTM_MOD value between the reading of the
TOF bit and the writing of 0 to the TOF bit, the process of clearing the
TOF bit does not work as expected when FTMx_CONF[NUMTOF] != 0 and the
current TOF count is less than FTMx_CONF[NUMTOF]. If the above condition
is met, the TOF bit remains set. If the TOF interrupt is enabled
(FTMx_SC[TOIE] = 1), the TOF interrupt also remains asserted.

Above is the errata discription

The workaround is clearing TOF bit until it is cleaned(FTM counter doesn't
always reache the FTM_MOD anyway),which may cost some cycles.

Signed-off-by: Meng Yi <meng.yi@....com>
---
Change from V1:
-add timeout into wile loop using a counter
---
 drivers/clocksource/fsl_ftm_timer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/clocksource/fsl_ftm_timer.c b/drivers/clocksource/fsl_ftm_timer.c
index 738515b..97bdb09 100644
--- a/drivers/clocksource/fsl_ftm_timer.c
+++ b/drivers/clocksource/fsl_ftm_timer.c
@@ -83,11 +83,11 @@ static inline void ftm_counter_disable(void __iomem *base)
 
 static inline void ftm_irq_acknowledge(void __iomem *base)
 {
-	u32 val;
+	u32 count = 100;
 
-	val = ftm_readl(base + FTM_SC);
-	val &= ~FTM_SC_TOF;
-	ftm_writel(val, base + FTM_SC);
+	while ((FTM_SC_TOF & ftm_readl(base + FTM_SC)) && count--)
+		ftm_writel(ftm_readl(base + FTM_SC) & (~FTM_SC_TOF),
+			   base + FTM_SC);
 }
 
 static inline void ftm_irq_enable(void __iomem *base)
-- 
2.1.0.27.g96db324