2018-03-16 16:25:09

by Sinan Kaya

Subject: [PATCH v3 11/18] qlcnic: Eliminate duplicate barriers on weakly-ordered archs

Code includes wmb() followed by writel(). writel() already has a
barrier on some architectures like arm64.

This ends up CPU observing two barriers back to back before executing
the register write.

Since code already has an explicit barrier call, changing writel() to
writel_relaxed().

Signed-off-by: Sinan Kaya <[email protected]>
---
drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
index 46b0372..97c146e7 100644
--- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
+++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
@@ -478,7 +478,7 @@ irqreturn_t qlcnic_83xx_clear_legacy_intr(struct qlcnic_adapter *adapter)
wmb();

/* clear the interrupt trigger control register */
- writel(0, adapter->isr_int_vec);
+ writel_relaxed(0, adapter->isr_int_vec);
intr_val = readl(adapter->isr_int_vec);
do {
intr_val = readl(adapter->tgt_status_reg);
--
2.7.4

2018-03-20 01:50:37

by Chopra, Manish

Subject: RE: [PATCH v3 11/18] qlcnic: Eliminate duplicate barriers on weakly-ordered archs

> -----Original Message-----
> From: Sinan Kaya [mailto:[email protected]]
> Sent: Friday, March 16, 2018 9:46 PM
> To: [email protected]; [email protected]; [email protected]
> Cc: [email protected]; [email protected];
> Sinan Kaya <[email protected]>; Patil, Harish <[email protected]>;
> Chopra, Manish <[email protected]>; Dept-GE Linux NIC Dev <Dept-
> [email protected]>; [email protected]
> Subject: [PATCH v3 11/18] qlcnic: Eliminate duplicate barriers on weakly-ordered
> archs
>
> Code includes wmb() followed by writel(). writel() already has a barrier on some
> architectures like arm64.
>
> This ends up CPU observing two barriers back to back before executing the
> register write.
>
> Since code already has an explicit barrier call, changing writel() to
> writel_relaxed().
>
> Signed-off-by: Sinan Kaya <[email protected]>
> ---
> drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
> b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
> index 46b0372..97c146e7 100644
> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_83xx_hw.c
> @@ -478,7 +478,7 @@ irqreturn_t qlcnic_83xx_clear_legacy_intr(struct
> qlcnic_adapter *adapter)
> wmb();
>
> /* clear the interrupt trigger control register */
> - writel(0, adapter->isr_int_vec);
> + writel_relaxed(0, adapter->isr_int_vec);
> intr_val = readl(adapter->isr_int_vec);
> do {
> intr_val = readl(adapter->tgt_status_reg);
> --
> 2.7.4

Acked-by: Manish Chopra <[email protected]>

Thanks.