From: Sekhar Nori <nsekhar@ti.com> To: "David S . Miller" <davem@davemloft.net> Cc: Grygorii Strashko <grygorii.strashko@ti.com>, <linux-omap@vger.kernel.org>, <netdev@vger.kernel.org>, Andrew Lunn <andrew@lunn.ch>, Sekhar Nori <nsekhar@ti.com> Subject: [PATCH v2 net-next] drivers: net: davinci_mdio: prevent spurious timeout Date: Wed, 9 May 2018 16:30:24 +0530 [thread overview] Message-ID: <20180509110024.1772-1-nsekhar@ti.com> (raw) A well timed kernel preemption in the time_after() loop in wait_for_idle() can result in a spurious timeout error to be returned. Fix it by using readl_poll_timeout() which takes care of this issue. Signed-off-by: Sekhar Nori <nsekhar@ti.com> --- v2: use readl_poll_timeout() per suggestion from Andrew. The issue has not been personally observed by me, but has been reported by users. Sending for next-next given the non-critical nature. There is seems to be no easy way to reproduce this. drivers/net/ethernet/ti/davinci_mdio.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/ti/davinci_mdio.c b/drivers/net/ethernet/ti/davinci_mdio.c index 3c33f4504d8e..d073432a5dbe 100644 --- a/drivers/net/ethernet/ti/davinci_mdio.c +++ b/drivers/net/ethernet/ti/davinci_mdio.c @@ -34,6 +34,7 @@ #include <linux/clk.h> #include <linux/err.h> #include <linux/io.h> +#include <linux/iopoll.h> #include <linux/pm_runtime.h> #include <linux/davinci_emac.h> #include <linux/of.h> @@ -227,14 +228,16 @@ static inline int wait_for_user_access(struct davinci_mdio_data *data) static inline int wait_for_idle(struct davinci_mdio_data *data) { struct davinci_mdio_regs __iomem *regs = data->regs; - unsigned long timeout = jiffies + msecs_to_jiffies(MDIO_TIMEOUT); + u32 val, ret; - while (time_after(timeout, jiffies)) { - if (__raw_readl(®s->control) & CONTROL_IDLE) - return 0; + ret = readl_poll_timeout(®s->control, val, val & CONTROL_IDLE, + 0, MDIO_TIMEOUT * 1000); + if (ret) { + dev_err(data->dev, "timed out waiting for idle\n"); + return ret; } - dev_err(data->dev, "timed out waiting for idle\n"); - return -ETIMEDOUT; + + return 0; } static int davinci_mdio_read(struct mii_bus *bus, int phy_id, int phy_reg) -- 2.16.2
WARNING: multiple messages have this Message-ID (diff)
From: Sekhar Nori <nsekhar@ti.com> To: "David S . Miller" <davem@davemloft.net> Cc: Grygorii Strashko <grygorii.strashko@ti.com>, linux-omap@vger.kernel.org, netdev@vger.kernel.org, Andrew Lunn <andrew@lunn.ch>, Sekhar Nori <nsekhar@ti.com> Subject: [PATCH v2 net-next] drivers: net: davinci_mdio: prevent spurious timeout Date: Wed, 9 May 2018 16:30:24 +0530 [thread overview] Message-ID: <20180509110024.1772-1-nsekhar@ti.com> (raw) A well timed kernel preemption in the time_after() loop in wait_for_idle() can result in a spurious timeout error to be returned. Fix it by using readl_poll_timeout() which takes care of this issue. Signed-off-by: Sekhar Nori <nsekhar@ti.com> --- v2: use readl_poll_timeout() per suggestion from Andrew. The issue has not been personally observed by me, but has been reported by users. Sending for next-next given the non-critical nature. There is seems to be no easy way to reproduce this. drivers/net/ethernet/ti/davinci_mdio.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/ti/davinci_mdio.c b/drivers/net/ethernet/ti/davinci_mdio.c index 3c33f4504d8e..d073432a5dbe 100644 --- a/drivers/net/ethernet/ti/davinci_mdio.c +++ b/drivers/net/ethernet/ti/davinci_mdio.c @@ -34,6 +34,7 @@ #include <linux/clk.h> #include <linux/err.h> #include <linux/io.h> +#include <linux/iopoll.h> #include <linux/pm_runtime.h> #include <linux/davinci_emac.h> #include <linux/of.h> @@ -227,14 +228,16 @@ static inline int wait_for_user_access(struct davinci_mdio_data *data) static inline int wait_for_idle(struct davinci_mdio_data *data) { struct davinci_mdio_regs __iomem *regs = data->regs; - unsigned long timeout = jiffies + msecs_to_jiffies(MDIO_TIMEOUT); + u32 val, ret; - while (time_after(timeout, jiffies)) { - if (__raw_readl(®s->control) & CONTROL_IDLE) - return 0; + ret = readl_poll_timeout(®s->control, val, val & CONTROL_IDLE, + 0, MDIO_TIMEOUT * 1000); + if (ret) { + dev_err(data->dev, "timed out waiting for idle\n"); + return ret; } - dev_err(data->dev, "timed out waiting for idle\n"); - return -ETIMEDOUT; + + return 0; } static int davinci_mdio_read(struct mii_bus *bus, int phy_id, int phy_reg) -- 2.16.2
next reply other threads:[~2018-05-09 11:00 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-05-09 11:00 Sekhar Nori [this message] 2018-05-09 11:00 ` [PATCH v2 net-next] drivers: net: davinci_mdio: prevent spurious timeout Sekhar Nori 2018-05-09 13:30 ` Andrew Lunn 2018-05-09 15:46 ` Sekhar Nori 2018-05-09 15:46 ` Sekhar Nori
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