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

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Message-ID: <8520D5D51A55D047800579B094147198263CCF7F@XAP-PVEXMBX02.xlnx.xilinx.com>
Date:   Tue, 24 Jan 2017 10:03:10 +0000
From:   Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
To:     Larry Finger <Larry.Finger@...inger.net>,
        "chaoming_li@...lsil.com.cn" <chaoming_li@...lsil.com.cn>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Ravikiran Gummaluri <rgummal@...inx.com>
Subject: RE: [PATCH] rtlwifi: rtl8192x: Enabling and disabling hardware
 interrupts after enabling local irq flags

> Subject: Re: [PATCH] rtlwifi: rtl8192x: Enabling and disabling hardware interrupts
> after enabling local irq flags
> 
> On 01/20/2017 08:14 AM, Bharat Kumar Gogada wrote:
> >  > On 01/19/2017 04:14 AM, Bharat Kumar Gogada wrote:
> >>> -Realtek 8192CE chipset maintains local irq flags after
> >>> enabling/disabling hardware interrupts.
> >>> -Hardware interrupts are enabled before enabling the local irq
> >>> flags(these flags are being checked in interrupt handler), leading
> >>> to race condition on some RP, where the irq line between bridge and
> >>> GIC goes high at ASSERT_INTx and goes low only at DEASSERT_INTx. In
> >>> this kind of RP by the time ASSERT_INTx is seen irq_enable flag is
> >>> still set to false, resulting in continuous interrupts seen by CPU
> >>> as DEASSERT_INTx cannot be sent since flag is still false and making
> >>> CPU stall.
> >>> -Changing the sequence of setting these irq flags.
> >>>
> >>> Signed-off-by: Bharat Kumar Gogada <bharatku@...inx.com>
> >>> ---
> >>
> >> This patch should be enhanced with the smb_xx() calls as suggested by by
> Lino.
> >>
> >> The subject should be changed. I would suggest something like "rtlwifi:
> >> rtl8192ce: Prevent race condition when enabling interrupts", as it
> >> explains the condition you are preventing.
> >>
> >> The other PCI drivers also have the same problem. Do you want to
> >> prepare the patches, or should I do it?
> >>
> > Thanks Larry. Please send out the patches adding the above enhancements
> suggested by Lino.
> 
> I have prepared a patch fixing all the drivers. By the way, what CPU hardware
> showed this problem?
> 
Thanks Larry, it was showed in ZynqUltrascalePlus Root Port hardware.