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Date: Wed, 14 Mar 2012 10:13:34 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Alexander Stein <alexander.stein@...tec-electronic.com>
CC: Chris Ball <cjb@...top.org>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org
Subject: Re: [PATCH 2/3] mmc: sdhci: check interrupt flags in ISR again
On 14/03/12 09:53, Alexander Stein wrote:
> Hello,
>
> Am Mittwoch, 14. März 2012, 09:39:02 schrieb Adrian Hunter:
>> On 13/03/12 19:16, Alexander Stein wrote:
>>> When using MSI it is possible that a new MSI is sent while an earlier
>>> MSI is currently handled. In this case SDHCI_INT_STATUS only contains
>>> SDHCI_INT_RESPONSE and the ISR would not be called again. But at the end
>>> of the ISR SDHCI_INT_DATA_END is now also pending which would be
>>> ignored.
>>>
>>> Fix this by rereading the interrupt flags in the ISR until no interrupt
>>> we care is pending.
>>>
>>> Signed-off-by: Alexander Stein <alexander.stein@...tec-electronic.com>
>> [...]
>>> @@ -2336,6 +2338,14 @@ static irqreturn_t sdhci_irq(int irq, void
>>> *dev_id)>
>>> sdhci_writel(host, SDHCI_INT_BUS_POWER, SDHCI_INT_STATUS);
>>>
>>> }
>>>
>>> + intmask_unhandled = intmask;
>>> +
>>> + intmask = sdhci_readl(host, SDHCI_INT_STATUS);
>>> +
>>> + /* Do interrupt handling again if we got new flags */
>>> + if (intmask & ~intmask_unhandled)
>>> + goto again;
>>> +
>>>
>>> intmask &= ~SDHCI_INT_BUS_POWER;
>>>
>>> if (intmask & SDHCI_INT_CARD_INT)
>>
>> Why not just replace mmiowb() i.e.
>>
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 8d66706..da8a101 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -2353,7 +2353,9 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
>>
>> result = IRQ_HANDLED;
>>
>> - mmiowb();
>> + intmask = sdhci_readl(host, SDHCI_INT_STATUS);
>> + if (intmask)
>> + goto again;
>> out:
>> spin_unlock(&host->lock);
>>
>
> Well, I chose this way to only printk the error once. With your suggestion it
> might be printed in each loop, dunno how often/fast these IRQ stats are set
> again after clearing. This would end in an endless loop if error flags are set
> again fast enough, but see below.
> But in general I like this approach.
>
>> But maybe it would be safer limiting the number of loops i.e.
>>
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index 8d66706..d88247d 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -2268,7 +2268,7 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
>> irqreturn_t result;
>> struct sdhci_host *host = dev_id;
>> u32 intmask;
>> - int cardint = 0;
>> + int cardint = 0, max_loops = 16;
>>
>> spin_lock(&host->lock);
>>
>> @@ -2353,7 +2353,9 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
>>
>> result = IRQ_HANDLED;
>>
>> - mmiowb();
>> + intmask = sdhci_readl(host, SDHCI_INT_STATUS);
>> + if (intmask && --max_loops)
>> + goto again;
>> out:
>> spin_unlock(&host->lock);
>
> The actual problem I saw was a CMD6 command with an R1b response where the IRQ
> for the 'not busy' event was sent during ISR for the response. So I think
> normally this should only occur once.
> Regarding error flags I masked the unhandled flags out in order to print an
> error only once, even if they might be set again in the next loop. With a
> simple check on intmask they might occur up to 16 times in the kernel log.
> IMHO it makes no sense to repeatedly print errors about interrupt flags we
> don't handle.
>
> Suggestions to get a more clean way?
I don't know about clean, but there is this:
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 8d66706..e0909da 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2267,8 +2267,8 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
{
irqreturn_t result;
struct sdhci_host *host = dev_id;
- u32 intmask;
- int cardint = 0;
+ u32 intmask, unexpected = 0;
+ int cardint = 0, max_loops = 16;
spin_lock(&host->lock);
@@ -2344,19 +2344,24 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
intmask &= ~SDHCI_INT_CARD_INT;
if (intmask) {
- pr_err("%s: Unexpected interrupt 0x%08x.\n",
- mmc_hostname(host->mmc), intmask);
- sdhci_dumpregs(host);
-
+ unexpected |= intmask;
sdhci_writel(host, intmask, SDHCI_INT_STATUS);
}
result = IRQ_HANDLED;
- mmiowb();
+ intmask = sdhci_readl(host, SDHCI_INT_STATUS);
+ if (intmask && --max_loops)
+ goto again;
out:
spin_unlock(&host->lock);
+ if (unexpected) {
+ pr_err("%s: Unexpected interrupt 0x%08x.\n",
+ mmc_hostname(host->mmc), unexpected);
+ sdhci_dumpregs(host);
+ }
+
/*
* We have to delay this as it calls back into the driver.
*/
--
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