linux-kernel - RE: [PATCH v7 RESEND 07/13] spi: imx: fix ERR009165

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Date:   Wed, 13 May 2020 09:36:59 +0000
From:   Robin Gong <yibin.gong@....com>
To:     Sascha Hauer <s.hauer@...gutronix.de>
CC:     "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "will.deacon@....com" <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        dl-linux-imx <linux-imx@....com>,
        "martin.fuzzey@...wbird.group" <martin.fuzzey@...wbird.group>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "l.stach@...gutronix.de" <l.stach@...gutronix.de>
Subject: RE: [PATCH v7 RESEND 07/13] spi: imx: fix ERR009165

On 2020/05/13 Sascha Hauer <s.hauer@...gutronix.de> wrote:
> On Wed, May 13, 2020 at 09:05:33AM +0000, Robin Gong wrote:
> > On 2020/05/13 Sascha Hauer <s.hauer@...gutronix.de> wrote:d
> > > >  drivers/spi/spi-imx.c | 16 ++++++++--------
> > > >  1 file changed, 8 insertions(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index
> > > > f4f28a4..70df8e6 100644
> > > > --- a/drivers/spi/spi-imx.c
> > > > +++ b/drivers/spi/spi-imx.c
> > > > @@ -585,8 +585,8 @@ static int mx51_ecspi_prepare_transfer(struct
> > > spi_imx_data *spi_imx,
> > > >  	ctrl |= mx51_ecspi_clkdiv(spi_imx, t->speed_hz, &clk);
> > > >  	spi_imx->spi_bus_clk = clk;
> > > >
> > > > -	if (spi_imx->usedma)
> > > > -		ctrl |= MX51_ECSPI_CTRL_SMC;
> > > > +	/* ERR009165: work in XHC mode as PIO */
> > > > +	ctrl &= ~MX51_ECSPI_CTRL_SMC;
> > > >
> > > >  	writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL);
> > > >
> > > > @@ -617,7 +617,7 @@ static void mx51_setup_wml(struct spi_imx_data
> > > *spi_imx)
> > > >  	 * and enable DMA request.
> > > >  	 */
> > > >  	writel(MX51_ECSPI_DMA_RX_WML(spi_imx->wml - 1) |
> > > > -		MX51_ECSPI_DMA_TX_WML(spi_imx->wml) |
> > > > +		MX51_ECSPI_DMA_TX_WML(0) |
> > > >  		MX51_ECSPI_DMA_RXT_WML(spi_imx->wml) |
> > > >  		MX51_ECSPI_DMA_TEDEN | MX51_ECSPI_DMA_RXDEN |
> > > >  		MX51_ECSPI_DMA_RXTDEN, spi_imx->base +
> MX51_ECSPI_DMA);
> > > @@ -1171,7
> > > > +1171,11 @@ static int spi_imx_dma_configure(struct spi_master
> > > > +*master)
> > > >  	tx.direction = DMA_MEM_TO_DEV;
> > > >  	tx.dst_addr = spi_imx->base_phys + MXC_CSPITXDATA;
> > > >  	tx.dst_addr_width = buswidth;
> > > > -	tx.dst_maxburst = spi_imx->wml;
> > > > +	/*
> > > > +	 * For ERR009165 with tx_wml = 0 could enlarge burst size to fifo size
> > > > +	 * to speed up fifo filling as possible.
> > > > +	 */
> > > > +	tx.dst_maxburst = spi_imx->devtype_data->fifo_size;
> > >
> > > In the next patch this is changed again to:
> > >
> > > +       if (spi_imx->devtype_data->tx_glitch_fixed)
> > > +               tx.dst_maxburst = spi_imx->wml;
> > > +       else
> > > +               tx.dst_maxburst = spi_imx->devtype_data->fifo_size;
> > >
> > > So with tx_glitch_fixed we end up with tx.dst_maxburst being the
> > > same as two patches before which is rather confusing. Better
> > > introduce tx_glitch_fixed in this patch, or maybe even merge this patch and
> the next one.
> > Sorry confused you, I should repleace 'tx_wml=0' in the above comments
> > with ' TX_THRESHOLD=0', which means tx transfer dma have to wait all
> > the tx data in tx fifo transferred with ERR009165 rather than
> > generically 'tx_wml' (for example --half fifo size used as
> > TX_THRESHOLD). Obviously TX_THRESHOLD=0 would down performance, so
> > enlarge dst_maxburst to fifo size as PIO with ERR009165. After
> > ERR009165 fixed at HW level. TX_THRESHOLD could be used as common
> > 'spi_imx->wml' so change it back. Will add more detail information in
> > v8.
> 
> I am not confused, I meant the patches are confusing. What you are doing
> is:
> 
> No patch:
> 	tx.dst_maxburst = a;
> 
> 1st patch
> 	tx.dst_maxburst = b;
> 
> 2nd patch:
> 
> 	if (foo)
> 		tx.dst_maxburst = a;
> 	else
> 		tx.dst_maxburst = b;
> 
> It would be better readable and understandable if you did that in one patch,
> because that would directly say "Under certain conditions we have to choose a,
> otherwise b". That's much better than changing "a" to "b" and then to "a or b"
> 
Okay, I'll merge those 2 changes into the next 08/13.