Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <fa92f431-500d-df0f-85f6-55cf5017a80b@quicinc.com>
Date:   Tue, 3 May 2022 19:22:28 -0700
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.8.1
Subject: Re: [PATCH 5/5] bus: mhi: host: Remove redundant dma_wmb() before ctx
 wp update
Content-Language: en-US
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        <mhi@lists.linux.dev>
CC:     <linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <quic_bbhatt@quicinc.com>, <loic.poulain@linaro.org>
References: <20220502104144.91806-1-manivannan.sadhasivam@linaro.org>
 <20220502104144.91806-6-manivannan.sadhasivam@linaro.org>
From:   Hemant Kumar <quic_hemantk@quicinc.com>
In-Reply-To: <20220502104144.91806-6-manivannan.sadhasivam@linaro.org>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk


On 5/2/2022 3:41 AM, Manivannan Sadhasivam wrote:
> The endpoint device will only read the context wp when the host rings
> the doorbell. And moreover the doorbell write is using writel(). This
> guarantess that the prior writes will be completed before ringing
> doorbell.
>
> So there is no need of an additional dma_wmb() to order the coherent
> memory writes w.r.t each other. Even if the writes gets reordered, it
> won't affect the endpoint device.
>
> Cc: Loic Poulain <loic.poulain@linaro.org>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> Reviewed by: Hemant Kumar <quic_hemantk@quicinc.com>
>