[PATCH v2] i2c: exynos5: disable fifo-almost-empty irq signal when necessary

[PATCH v2] i2c: exynos5: disable fifo-almost-empty irq signal when necessary

[Andrzej Hajda]

Fifo-almost-empty irq signal should be disabled as soon as possible,
to avoid unnecessary interrupt storm. The best moment is when there is
no more data to feed fifo.
This patch fixes system stalls caused by IRQ storm.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
---
v2:
    - removed doubled conditional

 drivers/i2c/busses/i2c-exynos5.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
index bea6071..00e81e3 100644
--- a/drivers/i2c/busses/i2c-exynos5.c
+++ b/drivers/i2c/busses/i2c-exynos5.c
@@ -502,8 +502,13 @@ static irqreturn_t exynos5_i2c_irq(int irqno, void *dev_id)
 		fifo_level = HSI2C_TX_FIFO_LVL(fifo_status);
 
 		len = i2c->variant->fifo_depth - fifo_level;
-		if (len > (i2c->msg->len - i2c->msg_ptr))
+		if (len > (i2c->msg->len - i2c->msg_ptr)) {
+			u32 int_en = readl(i2c->regs + HSI2C_INT_ENABLE);
+
+			int_en &= ~HSI2C_INT_TX_ALMOSTEMPTY_EN;
+			writel(int_en, i2c->regs + HSI2C_INT_ENABLE);
 			len = i2c->msg->len - i2c->msg_ptr;
+		}
 
 		while (len > 0) {
 			byte = i2c->msg->buf[i2c->msg_ptr++];
-- 
2.7.4

Re: [PATCH v2] i2c: exynos5: disable fifo-almost-empty irq signal when necessary

[Marek Szyprowski]

Hi,

On 2017-02-22 11:11, Andrzej Hajda wrote:
> Fifo-almost-empty irq signal should be disabled as soon as possible,
> to avoid unnecessary interrupt storm. The best moment is when there is
> no more data to feed fifo.
> This patch fixes system stalls caused by IRQ storm.
>
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

With this patch TM2 board boots fine on linux-next from 21st Feb 2017
and maxcpus=1 in kernel command line.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---
> v2:
>      - removed doubled conditional
>
>   drivers/i2c/busses/i2c-exynos5.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
> index bea6071..00e81e3 100644
> --- a/drivers/i2c/busses/i2c-exynos5.c
> +++ b/drivers/i2c/busses/i2c-exynos5.c
> @@ -502,8 +502,13 @@ static irqreturn_t exynos5_i2c_irq(int irqno, void *dev_id)
>   		fifo_level = HSI2C_TX_FIFO_LVL(fifo_status);
>   
>   		len = i2c->variant->fifo_depth - fifo_level;
> -		if (len > (i2c->msg->len - i2c->msg_ptr))
> +		if (len > (i2c->msg->len - i2c->msg_ptr)) {
> +			u32 int_en = readl(i2c->regs + HSI2C_INT_ENABLE);
> +
> +			int_en &= ~HSI2C_INT_TX_ALMOSTEMPTY_EN;
> +			writel(int_en, i2c->regs + HSI2C_INT_ENABLE);
>   			len = i2c->msg->len - i2c->msg_ptr;
> +		}
>   
>   		while (len > 0) {
>   			byte = i2c->msg->buf[i2c->msg_ptr++];

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v2] i2c: exynos5: disable fifo-almost-empty irq signal when necessary

[Andi Shyti]

Hi Andrzej,

On Wed, Feb 22, 2017 at 11:11:20AM +0100, Andrzej Hajda wrote:
> Fifo-almost-empty irq signal should be disabled as soon as possible,
> to avoid unnecessary interrupt storm. The best moment is when there is
> no more data to feed fifo.
> This patch fixes system stalls caused by IRQ storm.
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Looks good,

Tested-by: Andi Shyti <andi.shyti@samsung.com>
Reviewed-by: Andi Shyti <andi.shyti@samsung.com>

Thanks,
Andi

Re: [PATCH v2] i2c: exynos5: disable fifo-almost-empty irq signal when necessary

[Wolfram Sang]

[-- Attachment #1: Type: text/plain, Size: 418 bytes --]

On Wed, Feb 22, 2017 at 11:11:20AM +0100, Andrzej Hajda wrote:
> Fifo-almost-empty irq signal should be disabled as soon as possible,
> to avoid unnecessary interrupt storm. The best moment is when there is
> no more data to feed fifo.
> This patch fixes system stalls caused by IRQ storm.
> 
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>

Applied to for-next (will be in this merge window), thanks!


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]