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Subject: Re: [PATCH 2/4] mmc: Add virtual command queue support
To:     Baolin Wang <baolin.wang@linaro.org>, ulf.hansson@linaro.org,
        riteshh@codeaurora.org, asutoshd@codeaurora.org
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        linus.walleij@linaro.org, vincent.guittot@linaro.org,
        linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <cover.1567740135.git.baolin.wang@linaro.org>
 <14599f7165f23db2bf7b71a2596e808e2bc2056c.1567740135.git.baolin.wang@linaro.org>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
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Date:   Mon, 9 Sep 2019 15:01:32 +0300
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On 6/09/19 6:52 AM, Baolin Wang wrote:
> Now the MMC read/write stack will always wait for previous request is
> completed by mmc_blk_rw_wait(), before sending a new request to hardware,
> or queue a work to complete request, that will bring context switching
> overhead, especially for high I/O per second rates, to affect the IO
> performance.
> 
> Thus this patch introduces virtual command queue interface, which is
> similar with the hardware command queue engine's idea, that can remove
> the context switching.

CQHCI is a hardware interface for eMMC's that support command queuing.  What
you are doing is a software issue queue, unrelated to CQHCI.  I think you
should avoid all reference to CQHCI i.e. call it something else.