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

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Message-ID: <DB6PR04MB3223B95A627770601587A02A895A0@DB6PR04MB3223.eurprd04.prod.outlook.com>
Date:   Wed, 11 Jul 2018 07:14:35 +0000
From:   Robin Gong <yibin.gong@....com>
To:     "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
CC:     Vinod <vkoul@...nel.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        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: s.hauer@...gutronix.de [mailto:s.hauer@...gutronix.de]
> Sent: 2018年7月11日 14:54
> To: Robin Gong <yibin.gong@....com>
> Cc: Vinod <vkoul@...nel.org>; dan.j.williams@...el.com;
> shawnguo@...nel.org; 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 Wed, Jul 11, 2018 at 06:37:02AM +0000, Robin Gong wrote:
> >
> > > -----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?
> 
> Instead of doing heuristics to guess whether we are doing memcpy you could
> instead make memcpy the default when slave_config is not called, i.e. drop the
> if (!data) check completely.
Yes, for memcpy case, that's a good way, but how to warning the future case
Without setup 'chan->private'...
> 
> > >
> > > > +		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
> 
> The problem seems to be that we do not know whether we are doing memcpy
> or not. Normally we get the information how a channel is to be configured in
> dma_device->device_config, but this function is not called in the memcpy case.
> 
> An alternative might also be to do the setup in
> dma_device->device_prep_dma_memcpy.
Yes, I've think about it before, but such prepare steps only needed in once time...
> 
> Sascha
> 
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