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SubjectRE: [PATCH v1 3/4] dmaengine: imx-sdma: support dmatest
Date

> -----Original Message-----
> From: s.hauer@pengutronix.de [mailto:s.hauer@pengutronix.de]
> Sent: 2018年7月11日 14:54
> To: Robin Gong <yibin.gong@nxp.com>
> Cc: Vinod <vkoul@kernel.org>; dan.j.williams@intel.com;
> shawnguo@kernel.org; Fabio Estevam <fabio.estevam@nxp.com>;
> linux@armlinux.org.uk; linux-arm-kernel@lists.infradead.org;
> kernel@pengutronix.de; dmaengine@vger.kernel.org;
> linux-kernel@vger.kernel.org; dl-linux-imx <linux-imx@nxp.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@kernel.org]
> > > Sent: 2018年7月10日 23:33
> > > To: Robin Gong <yibin.gong@nxp.com>
> > > Cc: dan.j.williams@intel.com; shawnguo@kernel.org;
> > > s.hauer@pengutronix.de; Fabio Estevam <fabio.estevam@nxp.com>;
> > > linux@armlinux.org.uk; linux-arm-kernel@lists.infradead.org;
> > > kernel@pengutronix.de; dmaengine@vger.kernel.org;
> > > linux-kernel@vger.kernel.org; dl-linux-imx <linux-imx@nxp.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@nxp.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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