linux-kernel - RE: [PATCH v1 3/4] dmaengine: imx-sdma: support dmatest

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Date:   Wed, 11 Jul 2018 06:37:02 +0000
From:   Robin Gong <yibin.gong@....com>
To:     Vinod <vkoul@...nel.org>
CC:     "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v1 3/4] dmaengine: imx-sdma: support dmatest


> -----Original Message-----
> From: Vinod [mailto:vkoul@...nel.org]
> Sent: 2018年7月10日 23:33
> To: Robin Gong <yibin.gong@....com>
> Cc: dan.j.williams@...el.com; shawnguo@...nel.org;
> s.hauer@...gutronix.de; Fabio Estevam <fabio.estevam@....com>;
> linux@...linux.org.uk; linux-arm-kernel@...ts.infradead.org;
> kernel@...gutronix.de; dmaengine@...r.kernel.org;
> linux-kernel@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> Subject: Re: [PATCH v1 3/4] dmaengine: imx-sdma: support dmatest
> 
> On 11-07-18, 00:23, Robin Gong wrote:
> > dmatest(memcpy) will never call dmaengine_slave_config before prep,
> 
> and that should have been a hint to you that you should not expect that
> 
> > so jobs in dmaengine_slave_config need to be moved into somewhere
> > before device_prep_dma_memcpy. Besides, dmatest never setup chan
> > ->private as other common case like uart/audio/spi will always setup
> > chan->private. Here check it to judge if it's dmatest case and do
> > jobs in slave_config.
> 
> and you should not do anything for dmatest. Supporting it means memcpy
> implementation is not correct :)
Okay, I will any word about dmatest here since memcpy assume no calling
slave_config.
> 
> >
> > Signed-off-by: Robin Gong <yibin.gong@....com>
> > ---
> >  drivers/dma/imx-sdma.c | 37 ++++++++++++++++++++++++++++---------
> >  1 file changed, 28 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c index
> > ed2267d..48f3749 100644
> > --- a/drivers/dma/imx-sdma.c
> > +++ b/drivers/dma/imx-sdma.c
> > @@ -1222,10 +1222,36 @@ static int sdma_alloc_chan_resources(struct
> > dma_chan *chan)  {
> >  	struct sdma_channel *sdmac = to_sdma_chan(chan);
> >  	struct imx_dma_data *data = chan->private;
> > +	struct imx_dma_data default_data;
> >  	int prio, ret;
> >
> > -	if (!data)
> > -		return -EINVAL;
> > +	ret = clk_enable(sdmac->sdma->clk_ipg);
> > +	if (ret)
> > +		return ret;
> > +	ret = clk_enable(sdmac->sdma->clk_ahb);
> > +	if (ret)
> > +		goto disable_clk_ipg;
> > +	/*
> > +	 * dmatest(memcpy) will never call dmaengine_slave_config before prep,
> > +	 * so jobs in dmaengine_slave_config need to be moved into somewhere
> > +	 * before device_prep_dma_memcpy. Besides, dmatest never setup chan
> > +	 * ->private as other common cases like uart/audio/spi will setup
> > +	 * chan->private always. Here check it to judge if it's dmatest case
> > +	 * and do jobs in slave_config.
> > +	 */
> > +	if (!data) {
> > +		dev_warn(sdmac->sdma->dev, "dmatest is running?\n");
> 
> why is that a warning!
Current SDMA driver assume filter function to set chan->private with specific data 
(struct imx_dma_data dma_data)like below (sound/soc/fsl/fsl_asrc_dma.c):
static bool filter(struct dma_chan *chan, void *param)
{
        if (!imx_dma_is_general_purpose(chan))
                return false;
        chan->private = param;
        return true;
}

But in memcpy case, at lease dmatest case, no chan->private set in its filter function.
So here take dmatest a special case and do some prepare jobs for memcpy. But if the
Upper device driver call dma_request_channel() with their specific filter without
'chan->private' setting in the future. The warning message is a useful hint to them to
Add 'chan->private' in filter function.  Or doc it somewhere?
> 
> > +		sdmac->word_size  =  sdmac->sdma->dma_device.copy_align;
> > +		default_data.priority = 2;
> > +		default_data.peripheral_type = IMX_DMATYPE_MEMORY;
> > +		default_data.dma_request = 0;
> > +		default_data.dma_request2 = 0;
> > +		data = &default_data;
> > +
> > +		sdma_config_ownership(sdmac, false, true, false);
> > +		sdma_get_pc(sdmac, IMX_DMATYPE_MEMORY);
> > +		sdma_load_context(sdmac);
> > +	}
> 
> this needs to be default for memcpy
> 
> --
> ~Vinod