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

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Date:   Mon, 19 Mar 2018 20:10:28 +0000
From:   "Chopra, Manish" <Manish.Chopra@...ium.com>
To:     Sinan Kaya <okaya@...eaurora.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "timur@...eaurora.org" <timur@...eaurora.org>,
        "sulrich@...eaurora.org" <sulrich@...eaurora.org>
CC:     "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "Patil, Harish" <Harish.Patil@...ium.com>,
        Dept-GE Linux NIC Dev <Dept-GELinuxNICDev@...ium.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 11/18] qlcnic: Eliminate duplicate barriers on
 weakly-ordered archs

> -----Original Message-----
> From: Sinan Kaya [mailto:okaya@...eaurora.org]
> Sent: Friday, March 16, 2018 9:46 PM
> To: netdev@...r.kernel.org; timur@...eaurora.org; sulrich@...eaurora.org
> Cc: linux-arm-msm@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> Sinan Kaya <okaya@...eaurora.org>; Patil, Harish <Harish.Patil@...ium.com>;
> Chopra, Manish <Manish.Chopra@...ium.com>; Dept-GE Linux NIC Dev <Dept-
> GELinuxNICDev@...ium.com>; linux-kernel@...r.kernel.org
> 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 <okaya@...eaurora.org>
> ---
>  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 <manish.chopra@...ium.com>

Thanks.