linux-kernel - Re: [PATCH linux-next v3 1/1] spi: imx: dynamic burst length adjust for PIO mode

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Message-ID: <CAOMZO5D4O38M3ZQYxcT2w+oW=HBuk2WPMN7Ue4Va_gz3zbKZ=Q@mail.gmail.com>
Date:   Mon, 29 May 2017 08:07:42 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Jiada Wang <jiada_wang@...tor.com>
Cc:     Mark Brown <broonie@...nel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH linux-next v3 1/1] spi: imx: dynamic burst length adjust
 for PIO mode

Hi Jiada,

On Fri, May 26, 2017 at 2:02 AM,  <jiada_wang@...tor.com> wrote:
> From: Jiada Wang <jiada_wang@...tor.com>
>
> previously burst length (BURST_LENGTH) is always set to equal
> to bits_per_word, causes a 10us gap between each word in
> transfer, which significantly affects performance.
>
> This patch uses 32 bits transfer to simulate lower bits transfer,
> and adjusts burst length runtimely to use biggeest burst length
> as possible to reduce the gaps in transfer for PIO mode.

Just curious: what is the performance gain you observe with this patch?