From: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
To: Guenter Roeck <linux@roeck-us.net>,
Brendan Higgins <brendanhiggins@google.com>
Cc: linux-aspeed@lists.ozlabs.org, "Andrew Jeffery" <andrew@aj.id.au>,
openbmc@lists.ozlabs.org, linux-kernel@vger.kernel.org,
"Cédric Le Goater" <clg@kaod.org>,
linux-i2c@vger.kernel.org
Subject: Re: [PATCH] i2c: aspeed: Acknowledge most interrupts early in interrupt handler
Date: Fri, 14 Sep 2018 09:28:43 -0700 [thread overview]
Message-ID: <fbf54ca6-16b3-5e35-eac8-b3dab8118543@linux.intel.com> (raw)
In-Reply-To: <1536895810-28903-1-git-send-email-linux@roeck-us.net>
On 9/13/2018 8:30 PM, Guenter Roeck wrote:
> Commit 3e9efc3299dd ("i2c: aspeed: Handle master/slave combined irq events
> properly") moved interrupt acknowledgment to the end of the interrupt
> handler. In part this was done because the AST2500 datasheet says:
>
> I2CD10 Interrupt Status Register
> bit 2 Receive Done Interrupt status
> S/W needs to clear this status bit to allow next data receiving.
>
> Acknowledging Receive Done before receive data was handled resulted in
> receive errors on high speed I2C busses.
>
> However, interrupt acknowledgment was not only moved to the end of the
> interrupt handler for Receive Done Interrupt status, but for all interrupt
> status bits. This could result in race conditions if a second interrupt was
> received during interrupt handling and not handled but still acknowledged
> at the end of the interrupt handler.
>
> Acknowledge only "Receive Done Interrupt status" late in the interrupt
> handler to solve the problem.
>
> Fixes: 3e9efc3299dd ("i2c: aspeed: Handle master/slave combined irq events properly")
> Cc: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> Cc: Joel Stanley <joel@jms.id.au>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> drivers/i2c/busses/i2c-aspeed.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index c258c4d9a4c0..3d518e09369f 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -552,6 +552,9 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
>
> spin_lock(&bus->lock);
> irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
> + /* Ack all interrupts except for Rx done */
> + writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE,
> + bus->base + ASPEED_I2C_INTR_STS_REG);
> irq_remaining = irq_received;
>
> #if IS_ENABLED(CONFIG_I2C_SLAVE)
> @@ -584,8 +587,10 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
> "irq handled != irq. expected 0x%08x, but was 0x%08x\n",
> irq_received, irq_handled);
>
> - /* Ack all interrupt bits. */
> - writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG);
> + /* Ack Rx done */
> + if (irq_received & ASPEED_I2CD_INTR_RX_DONE)
> + writel(ASPEED_I2CD_INTR_RX_DONE,
> + bus->base + ASPEED_I2C_INTR_STS_REG);
> spin_unlock(&bus->lock);
> return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
> }
>
Looks good to me. Thanks! :)
Acked-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
next prev parent reply other threads:[~2018-09-14 16:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-14 3:30 [PATCH] i2c: aspeed: Acknowledge most interrupts early in interrupt handler Guenter Roeck
2018-09-14 16:28 ` Jae Hyun Yoo [this message]
2018-09-17 16:34 ` Wolfram Sang
2018-09-17 17:16 ` Jae Hyun Yoo
2018-09-17 18:48 ` Guenter Roeck
2018-09-18 1:11 ` Joel Stanley
2018-09-18 1:28 ` Brendan Higgins
2018-09-24 21:45 ` Wolfram Sang
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