linux-kernel - Re: [PATCH v4 1/2] phy: qcom: Add driver for QCOM APQ8064 SATA PHY

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Date:	Wed, 16 Jul 2014 07:28:16 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
CC:	Kishon Vijay Abraham I <kishon@...com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-ide@...r.kernel.org,
	Sujit Reddy Thumma <sthumma@...eaurora.org>
Subject: Re: [PATCH v4 1/2] phy: qcom: Add driver for QCOM APQ8064 SATA PHY


On 15/07/14 17:56, Bartlomiej Zolnierkiewicz wrote:
>> +
>> >+/* Helper function to do poll and timeout */
>> >+static int read_poll_timeout(void __iomem *addr, u32 mask)
>> >+{
>> >+	unsigned long timeout = jiffies + msecs_to_jiffies(TIMEOUT_MS);
>> >+
>> >+	do {
>> >+		if (readl_relaxed(addr) & mask)
>> >+			return 0;
>> >+
>> >+		 usleep_range(DELAY_INTERVAL_US, DELAY_INTERVAL_US + 50);
>> >+	} while (!time_after(jiffies, timeout));
>> >+
>> >+	return -ETIMEDOUT;
>> >+}
> Thanks for reworking this code, unfortunately it still has a one
> (unlikely but still theoretically possible) problem.  If there is
> i.e. a big IRQ load between first usleep_range() call and first

Very unlikely but as you said it possible in theory :-)

> time_after() check the function will timeout without checking
> the register.  To fix it you needs to add an additonal register
> checking before returning -ETIMEDOUT value or replace time_after()
> condition with a fixed number of retries (100000 to cover 1sec
> timeout).
I will send out a fix on top of my previous patches to fix this.

thanks,
srini
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