linux-kernel - Re: [PATCH] rtlwifi: rtl8192x: Enabling and disabling hardware interrupts after enabling local irq flags

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Date:   Thu, 19 Jan 2017 15:35:38 +0100
From:   "Lino Sanfilippo" <LinoSanfilippo@....de>
To:     "Bharat Kumar Gogada" <bharat.kumar.gogada@...inx.com>
Cc:     Larry.Finger@...inger.net, chaoming_li@...lsil.com.cn,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvalo@...eaurora.org, netdev@...r.kernel.org, rgummal@...inx.com,
        "Bharat Kumar Gogada" <bharatku@...inx.com>
Subject: Re: [PATCH] rtlwifi: rtl8192x: Enabling and disabling hardware
 interrupts after enabling local irq flags

Hi,

altek/rtlwifi/rtl8192ce/hw.c b/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/hw.c
> index a47be73..143766c4 100644
> --- a/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/hw.c
> +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8192ce/hw.c
> @@ -1306,9 +1306,9 @@ void rtl92ce_enable_interrupt(struct ieee80211_hw *hw)
>  	struct rtl_priv *rtlpriv = rtl_priv(hw);
>  	struct rtl_pci *rtlpci = rtl_pcidev(rtl_pcipriv(hw));
>  
> +	rtlpci->irq_enabled = true;
>  	rtl_write_dword(rtlpriv, REG_HIMR, rtlpci->irq_mask[0] & 0xFFFFFFFF);
>  	rtl_write_dword(rtlpriv, REG_HIMRE, rtlpci->irq_mask[1] & 0xFFFFFFFF);
> -	rtlpci->irq_enabled = true;
>  }
>  
>  void rtl92ce_disable_interrupt(struct ieee80211_hw *hw)
> @@ -1316,9 +1316,9 @@ void rtl92ce_disable_interrupt(struct ieee80211_hw *hw)
>  	struct rtl_priv *rtlpriv = rtl_priv(hw);
>  	struct rtl_pci *rtlpci = rtl_pcidev(rtl_pcipriv(hw));
>  
> +	rtlpci->irq_enabled = false;
>  	rtl_write_dword(rtlpriv, REG_HIMR, IMR8190_DISABLED);
>  	rtl_write_dword(rtlpriv, REG_HIMRE, IMR8190_DISABLED);
> -	rtlpci->irq_enabled = false;
>  }
>  

AFAIK you also have to use memory barriers here to ensure that
the concerning instructions are not reordered, and both irq handler
and process have a consistent perception of irq_enabled, e.g:

rtlpci->irq_enabled = true;
smp_wmb();
rtl_write_dword(rtlpriv, REG_HIMR, rtlpci->irq_mask[0] & 0xFFFFFFFF);

and in the irq handler

if (rtlpci->irq_enabled == 0) {
        smp_rmb();
	return ret;
}


Regards,
Lino