On Wednesday 09 May 2018 07:00 PM, Andrew Lunn wrote:
> On Wed, May 09, 2018 at 04:30:24PM +0530, Sekhar Nori wrote:
>> 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@xxxxxx>
>> ---
>> 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;
>> }
>
> Hi Sekhar
>
> You could simplify this to:
>
>> + if (ret)
>> + dev_err(data->dev, "timed out waiting for idle\n");
>> + return ret;
>
> Reviewed-by: Andrew Lunn <andrew@xxxxxxx>
Indeed. v3 sent.
Thanks,
Sekhar
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