linux-kernel - Re: [EXT] Re: [PATCH v2 06/15] spi: imx: fix ERR009165

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Date:   Fri, 26 Apr 2019 11:37:22 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Robin Gong <yibin.gong@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "plyatov@...il.com" <plyatov@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
Cc:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [EXT] Re: [PATCH v2 06/15] spi: imx: fix ERR009165

Am Freitag, den 26.04.2019, 09:22 +0000 schrieb Robin Gong:
> On 2019-04-26 at 11:07 +0200, Lucas Stach wrote:
> > 
> > Am Freitag, den 26.04.2019, 08:05 +0000 schrieb Robin Gong:
> > >  static void mx51_setup_wml(struct spi_imx_data *spi_imx)
> > >  {
> > > +     u32 tx_wml = 0;
> > > +
> > 
> > With a wml of 0 you might set the maxburst of the TX dma channel to
> > fifosize to minimize the performance impact of this workaround.
> > 
> > Regards,
> > Lucas
> 
> Unfortunately, this is a MUST part of errata which cause performance
> drop.

I'm not talking about changing the WML, but when the WML must be 0 you
can safely increase the DMA burst size without overflowing the FIFO,
which might recover some of of the performance loss.

Regards,
Lucas