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    SubjectRE: [PATCH v1 3/4] dmaengine: imx-sdma: support dmatest
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    > -----Original Message-----
    > From: Vinod [mailto:vkoul@kernel.org]
    > Sent: 2018年7月11日 15:19
    > To: s.hauer@pengutronix.de
    > Cc: Robin Gong <yibin.gong@nxp.com>; 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 11-07-18, 08:53, s.hauer@pengutronix.de wrote:
    > > 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
    > > > > > chan->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.
    > >
    > > > >
    > > > > > + 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.
    >
    > Not really true, device_config only provides parameters to be configured for
    > next slave transaction
    >
    > > An alternative might also be to do the setup in
    > dma_device->device_prep_dma_memcpy.
    >
    > Precisely, see how other drivers do this
    >
    > Let's roll back a bit and foresee why is this required.
    >
    > In case of memcpy, you need to tell DMA to do transfer from src to dstn and
    > size. Additional parameters like buswidth etc should be derived for maximum
    > throughput (after all we are dma, people want it to be done
    > fastest)
    >
    > Now for slave, you are interfacing with a peripheral and don't know how that is
    > setup. So you need to match the parameters, otherwise you get overflow or
    > underflow and hence need for device_config
    >
    > Please do not derive additional notions from these, please do not assume
    > anything else, unless provided in documentation :)
    I will move such prepare jobs from slave_config to device_prep_dma_memcpy
    Instead of device_alloc_chan_resources as I did in v1, thus we have no 'chan->private'
    issue, just like drivers/dma/stm32-mdma.c. The only limitation is those prepare jobs
    (some register setting) will be done every time memcpy instead of only one time in slave_config
    or v1 case. Is that ok?
    >
    > In doubt, just ask!
    >
    > HTH
    > --
    > ~Vinod
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