Matthew Garrett @ 2020-10-15 15:39 MST:
> On Thu, Oct 15, 2020 at 2:44 PM Jerry Snitselaar <jsnit...@redhat.com> wrote:
>>
>> There is a misconfiguration in the bios of the gpio pin used for the
>> interrupt in the T490s. When interrupts are enabled in the tpm_tis
>> driver code this results in an interrupt storm. This was initially
>> reported when we attempted to enable the interrupt code in the tpm_tis
>> driver, which previously wasn't setting a flag to enable it. Due to
>> the reports of the interrupt storm that code was reverted and we went back
>> to polling instead of using interrupts. Now that we know the T490s problem
>> is a firmware issue, add code to check if the system is a T490s and
>> disable interrupts if that is the case. This will allow us to enable
>> interrupts for everyone else. If the user has a fixed bios they can
>> force the enabling of interrupts with tpm_tis.interrupts=1 on the
>> kernel command line.
>
> I think an implication of this is that systems haven't been
> well-tested with interrupts enabled. In general when we've found a
> firmware issue in one place it ends up happening elsewhere as well, so
> it wouldn't surprise me if there are other machines that will also be
> unhappy with interrupts enabled. Would it be possible to automatically
> detect this case (eg, if we get more than a certain number of
> interrupts in a certain timeframe immediately after enabling the
> interrupt) and automatically fall back to polling in that case? It
> would also mean that users with fixed firmware wouldn't need to pass a
> parameter.
I believe Matthew is correct here. I found another system today
with completely different vendor for both the system and the tpm chip.
In addition another Lenovo model, the L490, has the issue.
This initial attempt at a solution like Matthew suggested works on
the system I found today, but I imagine it is all sorts of wrong.
In the 2 systems where I've seen it, there are about 100000 interrupts
in around 1.5 seconds, and then the irq code shuts down the interrupt
because they aren't being handled.
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 49ae09ac604f..478e9d02a3fa 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -27,6 +27,11 @@
#include "tpm.h"
#include "tpm_tis_core.h"
+static unsigned int time_start = 0;
+static bool storm_check = true;
+static bool storm_killed = false;
+static u32 irqs_fired = 0;
+
static void tpm_tis_clkrun_enable(struct tpm_chip *chip, bool value);
static void tpm_tis_enable_interrupt(struct tpm_chip *chip, u8 mask)
@@ -464,25 +469,31 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const
u8 *buf, size_t len)
return rc;
}
-static void disable_interrupts(struct tpm_chip *chip)
+static void __disable_interrupts(struct tpm_chip *chip)
{
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
u32 intmask;
int rc;
- if (priv->irq == 0)
- return;
-
rc = tpm_tis_read32(priv, TPM_INT_ENABLE(priv->locality), &intmask);
if (rc < 0)
intmask = 0;
intmask &= ~TPM_GLOBAL_INT_ENABLE;
rc = tpm_tis_write32(priv, TPM_INT_ENABLE(priv->locality), intmask);
+ chip->flags &= ~TPM_CHIP_FLAG_IRQ;
+}
+
+static void disable_interrupts(struct tpm_chip *chip)
+{
+ struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
+ if (priv->irq == 0)
+ return;
+
+ __disable_interrupts(chip);
devm_free_irq(chip->dev.parent, priv->irq, chip);
priv->irq = 0;
- chip->flags &= ~TPM_CHIP_FLAG_IRQ;
}
/*
@@ -528,6 +539,12 @@ static int tpm_tis_send(struct tpm_chip *chip, u8 *buf,
size_t len)
int rc, irq;
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
+ if (unlikely(storm_killed)) {
+ devm_free_irq(chip->dev.parent, priv->irq, chip);
+ priv->irq = 0;
+ storm_killed = false;
+ }
+
if (!(chip->flags & TPM_CHIP_FLAG_IRQ) || priv->irq_tested)
return tpm_tis_send_main(chip, buf, len);
@@ -748,6 +765,21 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
u32 interrupt;
int i, rc;
+ if (storm_check) {
+ irqs_fired++;
+
+ if (!time_start) {
+ time_start = jiffies_to_msecs(jiffies);
+ } else if ((irqs_fired > 1000) && (jiffies_to_msecs(jiffies) -
jiffies < 500)) {
+ __disable_interrupts(chip);
+ storm_check = false;
+ storm_killed = true;
+ return IRQ_HANDLED;
+ } else if ((jiffies_to_msecs(jiffies) - time_start > 500) &&
(irqs_fired < 1000)) {
+ storm_check = false;
+ }
+ }
+
rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &interrupt);
if (rc < 0)
return IRQ_NONE;
