Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
Message-ID: <b463bfc3-d18c-4d6c-bde7-f79f7e38fb2f@quicinc.com>
Date:   Mon, 20 Nov 2023 07:52:01 -0800
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 1/7] wifi: ath12k: get msi_data again after request_irq is
 called
Content-Language: en-US
To:     Kang Yang <quic_kangyang@quicinc.com>, <ath12k@lists.infradead.org>
CC:     <linux-wireless@vger.kernel.org>
References: <20231120101543.4369-1-quic_kangyang@quicinc.com>
 <20231120101543.4369-2-quic_kangyang@quicinc.com>
From:   Jeff Johnson <quic_jjohnson@quicinc.com>
In-Reply-To: <20231120101543.4369-2-quic_kangyang@quicinc.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 11/20/2023 2:15 AM, Kang Yang wrote:
> The reservation mode of interrupts in kernel assigns a dummy vector
> when the interrupt is allocated and assigns a real vector when the
> request_irq is called. The reservation mode helps to ease vector
> pressure when devices with a large amount of queues/interrupts are
> initialized, but only a minimal subset of those queues/interrupts
> is actually used.
> 
> So on reservation mode, the msi_data may change after request_irq is
> called, then it will lead to spurious interrupt. But when VT-d in
> BIOS is enabled and ath12k can get 32 MSI vectors, ath12k always get
> the same msi_data before and after request_irq.
> 
> So in case of one MSI vector, ath12k need read msi_data again after
> request_irq is called, and then the correct msi_data is programmed
> into WCN7850 hardware components.
> 
> Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0-03427-QCAHMTSWPL_V1.0_V2.0_SILICONZ-1.15378.4
> 
> Signed-off-by: Kang Yang <quic_kangyang@quicinc.com>
Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>