[1/1] net: socionext: clear rx irq correctly

Message ID 1539260906-29596-1-git-send-email-ilias.apalodimas@linaro.org
State New
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  • [1/1] net: socionext: clear rx irq correctly
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Commit Message

Ilias Apalodimas Oct. 11, 2018, 12:28 p.m.
commit 63ae7949e94a ("net: socionext: Use descriptor info instead of MMIO reads on Rx")
removed constant mmio reads from the driver and started using a descriptor 
field to check if packet should be processed.
This lead the napi rx handler being constantly called while no packets
needed processing and ksoftirq getting 100% cpu usage. Issue one mmio read 
to clear the irq correcty after processing packets

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 drivers/net/ethernet/socionext/netsec.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

-- 
2.7.4

Comments

Ard Biesheuvel Oct. 11, 2018, 1:49 p.m. | #1
On 11 October 2018 at 14:28, Ilias Apalodimas
<ilias.apalodimas@linaro.org> wrote:
> commit 63ae7949e94a ("net: socionext: Use descriptor info instead of MMIO reads on Rx")

> removed constant mmio reads from the driver and started using a descriptor

> field to check if packet should be processed.

> This lead the napi rx handler being constantly called while no packets

> needed processing and ksoftirq getting 100% cpu usage. Issue one mmio read

> to clear the irq correcty after processing packets

>

> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

> Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>


Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>


> ---

>  drivers/net/ethernet/socionext/netsec.c | 5 ++++-

>  1 file changed, 4 insertions(+), 1 deletion(-)

>

> diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c

> index 7aa5ebb..4289ccb 100644

> --- a/drivers/net/ethernet/socionext/netsec.c

> +++ b/drivers/net/ethernet/socionext/netsec.c

> @@ -735,8 +735,11 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)

>                 u16 idx = dring->tail;

>                 struct netsec_de *de = dring->vaddr + (DESC_SZ * idx);

>

> -               if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD))

> +               if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD)) {

> +                       /* reading the register clears the irq */

> +                       netsec_read(priv, NETSEC_REG_NRM_RX_PKTCNT);

>                         break;

> +               }

>

>                 /* This  barrier is needed to keep us from reading

>                  * any other fields out of the netsec_de until we have

> --

> 2.7.4

>
David Miller Oct. 11, 2018, 7:04 p.m. | #2
From: Ilias Apalodimas <ilias.apalodimas@linaro.org>

Date: Thu, 11 Oct 2018 15:28:26 +0300

> commit 63ae7949e94a ("net: socionext: Use descriptor info instead of MMIO reads on Rx")

> removed constant mmio reads from the driver and started using a descriptor 

> field to check if packet should be processed.

> This lead the napi rx handler being constantly called while no packets

> needed processing and ksoftirq getting 100% cpu usage. Issue one mmio read 

> to clear the irq correcty after processing packets

> 

> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

> Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>


Applied.

Patch

diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
index 7aa5ebb..4289ccb 100644
--- a/drivers/net/ethernet/socionext/netsec.c
+++ b/drivers/net/ethernet/socionext/netsec.c
@@ -735,8 +735,11 @@  static int netsec_process_rx(struct netsec_priv *priv, int budget)
 		u16 idx = dring->tail;
 		struct netsec_de *de = dring->vaddr + (DESC_SZ * idx);
 
-		if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD))
+		if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD)) {
+			/* reading the register clears the irq */
+			netsec_read(priv, NETSEC_REG_NRM_RX_PKTCNT);
 			break;
+		}
 
 		/* This  barrier is needed to keep us from reading
 		 * any other fields out of the netsec_de until we have