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Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting channel

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  Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting  channel Vinod Koul <vinod.koul@intel.com> - 2015-12-01 18:00 +0100
    Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting channel Arnd Bergmann <arnd@arndb.de> - 2015-12-01 21:20 +0100
      Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting  channel Vinod Koul <vinod.koul@intel.com> - 2015-12-02 05:50 +0100
        Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting channel Arnd Bergmann <arnd@arndb.de> - 2015-12-02 09:30 +0100
      Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting  channel Peter Ujfalusi <peter.ujfalusi@ti.com> - 2015-12-02 13:40 +0100

#1281048 — Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting channel

On Mon, Nov 30, 2015 at 03:45:30PM +0200, Peter Ujfalusi wrote:
> Hi,
> 
> Changes since RFC v01:
> - dma_request_chan(); lost the mask parameter
> - The new API does not rely on RESOURCE_DMA, instead the dma_filter_map table
>   will be used to provide the needed information to the filter function in
>   legacy mode
> - Extended the example patches to convert most of daVinci to use the new API to
>   request the DMA channels.

Hi Peter,

Thanks a bunch for fixing this up!

I think overall I am happy with the proposal and aligning with 2 APIs really
_helps_.

> 
> TODO: Documentation update ;)
>
> 
> As it has been discussed in the following thread:
> http://www.gossamer-threads.com/lists/linux/kernel/2181487#2181487
> 
> Andy: I did looked at the unified device properties, but I decided to not to use
> it as I don't see it to fit well and most of the legacy board files are using
> resources to specify at least their memory regions so adding the DMA resource
> to them would be more inline with the rest of the code.

I think that is okay for now, we can align on that eventually. I think this
doesn't impact the API design though..

> 
> The ARM, mmc and spi patches are converting daVinci drivers board files to use
> the new method of requesting DMA channel.
> 
> With this series I have taken a path which would result two new API, which can
> be used to convert most of the current users already and with some work all
> users might be able to move to this set.
> With this set the filter_fn used for legacy (non DT/ACPI) channel request is no
> longer needed to be exported to client drivers since the selection of the
> correct filter_fn will be done in the core.
> 
> So, the first proposal is to have:
> 
> struct dma_chan *dma_request_chan(struct device *dev, const char *name);
> struct dma_chan *dma_request_chan_by_mask(const dma_cap_mask_t *mask);
> 
> The dma_request_chan_by_mask() is to request any channel matching with the
> requested capabilities, can be used to request channel for memcpy, memset, xor,
> etc where no hardware synchronization is needed.
> 
> The dma_request_chan() is to request a slave channel. The dma_request_chan() will try to find the
> channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode
> it will use a filter lookup table and retrieves the needed information from
> the dma_filter_map provided by the DMA drivers.

That sounds right, for the third case would the arch, driver or someone else
configure this?

> This legacy mode needs changes in platform code, in dmaengine drivers and
> finally the dmaengine user drivers can be converted:

Are you marking the current APIs as dericated in the end of this series

> 
> For each dmaengine driver an array of DMA device, slave and the parameter
> for the filter function needs to be added:
> 
> static struct dma_filter_map da830_edma_map[] = {
> 	DMA_FILTER_ENTRY("davinci-mcasp.0", "rx", EDMA_CTLR_CHAN(0, 0)),
> 	DMA_FILTER_ENTRY("davinci-mcasp.0", "tx", EDMA_CTLR_CHAN(0, 1)),
> 	DMA_FILTER_ENTRY("davinci-mcasp.1", "rx", EDMA_CTLR_CHAN(0, 2)),
> 	DMA_FILTER_ENTRY("davinci-mcasp.1", "tx", EDMA_CTLR_CHAN(0, 3)),
> 	DMA_FILTER_ENTRY("davinci-mcasp.2", "rx", EDMA_CTLR_CHAN(0, 4)),
> 	DMA_FILTER_ENTRY("davinci-mcasp.2", "tx", EDMA_CTLR_CHAN(0, 5)),
> 	DMA_FILTER_ENTRY("spi_davinci.0", "rx", EDMA_CTLR_CHAN(0, 14)),
> 	DMA_FILTER_ENTRY("spi_davinci.0", "tx", EDMA_CTLR_CHAN(0, 15)),
> 	DMA_FILTER_ENTRY("da830-mmc.0", "rx", EDMA_CTLR_CHAN(0, 16)),
> 	DMA_FILTER_ENTRY("da830-mmc.0", "tx", EDMA_CTLR_CHAN(0, 17)),
> 	DMA_FILTER_ENTRY("spi_davinci.1", "rx", EDMA_CTLR_CHAN(0, 18)),
> 	DMA_FILTER_ENTRY("spi_davinci.1", "tx", EDMA_CTLR_CHAN(0, 19)),
> };
> 
> This information is going to be needed by the dmaengine driver, so
> modification to the platform_data is needed, and the driver map should be
> added to the pdata of the DMA driver:
> 
> da8xx_edma0_pdata.filter_map = da830_edma_map;
> da8xx_edma0_pdata.filtercnt = ARRAY_SIZE(da830_edma_map);
> 
> The DMA driver then needs to convigure the needed device -> filter_fn
> mapping before it registers with dma_async_device_register() :
> 
> if (info->filter_map) {
> 	ecc->dma_slave.filter_map.map = info->filter_map;
> 	ecc->dma_slave.filter_map.mapcnt = info->filtercnt;
> 	ecc->dma_slave.filter_map.filter_fn = edma_filter_for_map;
> }
> 
> When neither DT or ACPI lookup is available the dma_request_chan() will
> try to match the requester's device name with the filter_map's list of
> device names, when a match found it will use the information from the
> dma_filter_map to get the channel with the dma_get_channel() internal
> function.
> 
> Regards,
> Peter
> ---
> Peter Ujfalusi (15):
>   dmaengine: core: Allow NULL mask pointer in
>     __dma_device_satisfies_mask()
>   dmaengine: core: Move and merge the code paths using private_candidate
>   dmaengine: core: Introduce new, universal API to request a channel
>   dmaengine: edma: Add support for DMA filter mapping to slave devices
>   ARM: davinci: devices-da8xx: Add dma_filter_map to edma
>   ARM: davinci: dm355: Add dma_filter_map to edma
>   ARM: davinci: dm365: Add dma_filter_map to edma
>   ARM: davinci: dm644x: Add dma_filter_map to edma
>   ARM: davinci: dm646x: Add dma_filter_map to edma
>   mmc: davinci_mmc: Use dma_request_chan() to requesting DMA channel
>   spi: davinci: Use dma_request_chan() to requesting DMA channel
>   ARM: davinci: devices-da8xx: Remove DMA resources for MMC and SPI
>   ARM: davinci: devices: Remove DMA resources for MMC
>   ARM: davinci: dm355: Remove DMA resources for SPI
>   ARM: davinci: dm365: Remove DMA resources for SPI
> 
>  arch/arm/mach-davinci/devices-da8xx.c |  95 ++++++++++----------
>  arch/arm/mach-davinci/devices.c       |  19 ----
>  arch/arm/mach-davinci/dm355.c         |  28 ++++--
>  arch/arm/mach-davinci/dm365.c         |  30 +++++--
>  arch/arm/mach-davinci/dm644x.c        |  12 +++
>  arch/arm/mach-davinci/dm646x.c        |  11 +++
>  drivers/dma/dmaengine.c               | 160 +++++++++++++++++++++++++---------
>  drivers/dma/edma.c                    |  24 +++++
>  drivers/mmc/host/davinci_mmc.c        |  52 +++--------
>  drivers/spi/spi-davinci.c             |  76 +++++-----------
>  include/linux/dmaengine.h             |  31 +++++++
>  include/linux/platform_data/edma.h    |   5 ++
>  12 files changed, 330 insertions(+), 213 deletions(-)
> 
> -- 
> 2.6.3
> 

-- 
~Vinod
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#1281168 — Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting channel

On Tuesday 01 December 2015 22:29:54 Vinod Koul wrote:
> On Mon, Nov 30, 2015 at 03:45:30PM +0200, Peter Ujfalusi wrote:
> > channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode
> > it will use a filter lookup table and retrieves the needed information from
> > the dma_filter_map provided by the DMA drivers.
> 
> That sounds right, for the third case would the arch, driver or someone else
> configure this?

The typical case is for the configuration to be defined in arch or platform
code and passed down to the dmaengine driver.

I just noticed that the text above (and probably the code too) should
be changed so we always fall back to this. There are cases where the
platform is booted with DT in principle, but the DMA engine does not
(yet) use DT and still wants to be converted. I think we can easily
handle that case by always trying this if the other methods fail.

> > This legacy mode needs changes in platform code, in dmaengine drivers and
> > finally the dmaengine user drivers can be converted:
> 
> Are you marking the current APIs as dericated in the end of this series

I think we practically stopped marking things as deprecated in general.
Per Linus decree, whenever we want to get rid of something, we should
instead change all users in tree and then remove the API, expecting
driver maintainers to do something just because you marked it as deprecated
often doesn't work.

I can help out converting a few platforms, maybe one interface at a time.
This is what I see:

arnd@wuerfel:~/arm-soc$ for i in dma_request_slave_channel_reason dma_request_slave_channel dma_request_slave_channel_compat dma_request_channel  ; do echo `git grep -wl $i drivers/  | grep -v drivers/dma | wc -l`\      $i ; done
14      dma_request_slave_channel_reason
27      dma_request_slave_channel
25      dma_request_slave_channel_compat
34      dma_request_channel

I would probably leave the users of dma_request_channel() while converting
the others, as that is still used by all the platforms that don't use any DT
support.

Changing dma_request_slave_channel_reason and dma_request_slave_channel is
trivial, we can probably use coccinelle for that, as it does not require
any platform changes. That brings us to the users of
dma_request_slave_channel_compat, which currently includes these files:

$ git grep -wl dma_request_slave_channel_compat drivers/ata/pata_pxa.c
drivers/crypto/atmel-aes.c
drivers/crypto/atmel-sha.c
drivers/crypto/atmel-tdes.c
drivers/crypto/omap-aes.c
drivers/crypto/omap-des.c
drivers/crypto/omap-sham.c
drivers/media/platform/omap3isp/isphist.c
drivers/mmc/host/davinci_mmc.c
drivers/mmc/host/omap.c
drivers/mmc/host/omap_hsmmc.c
drivers/mmc/host/pxamci.c
drivers/mmc/host/s3cmci.c
drivers/mmc/host/tmio_mmc_dma.c
drivers/mtd/nand/pxa3xx_nand.c
drivers/net/ethernet/smsc/smc91x.c
drivers/net/irda/pxaficp_ir.c
drivers/spi/spi-omap2-mcspi.c
drivers/spi/spi-pxa2xx-dma.c
drivers/spi/spi-rspi.c
drivers/spi/spi-s3c64xx.c
drivers/spi/spi-sh-msiof.c
drivers/tty/serial/8250/8250_dma.c
drivers/tty/serial/samsung.c
drivers/tty/serial/sh-sci.c
include/linux/dmaengine.h

In other words: arch/avr32 and arch/sh along with omap1, omap2, davinci, pxa, and s3c
in terms of ARM platforms.

	Arnd
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#1281443

On Tue, Dec 01, 2015 at 09:17:06PM +0100, Arnd Bergmann wrote:
> On Tuesday 01 December 2015 22:29:54 Vinod Koul wrote:
> > On Mon, Nov 30, 2015 at 03:45:30PM +0200, Peter Ujfalusi wrote:
> > > channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode
> > > it will use a filter lookup table and retrieves the needed information from
> > > the dma_filter_map provided by the DMA drivers.
> > 
> > That sounds right, for the third case would the arch, driver or someone else
> > configure this?
> 
> The typical case is for the configuration to be defined in arch or platform
> code and passed down to the dmaengine driver.
> 
> I just noticed that the text above (and probably the code too) should
> be changed so we always fall back to this. There are cases where the
> platform is booted with DT in principle, but the DMA engine does not
> (yet) use DT and still wants to be converted. I think we can easily
> handle that case by always trying this if the other methods fail.

I agree that this makes sense, not just for DT cases but ACPI as well

> 
> > > This legacy mode needs changes in platform code, in dmaengine drivers and
> > > finally the dmaengine user drivers can be converted:
> > 
> > Are you marking the current APIs as dericated in the end of this series
> 
> I think we practically stopped marking things as deprecated in general.
> Per Linus decree, whenever we want to get rid of something, we should
> instead change all users in tree and then remove the API, expecting
> driver maintainers to do something just because you marked it as deprecated
> often doesn't work.

Yes but while we do conversion we don't know if new users get added which use
old API..

> 
> I can help out converting a few platforms, maybe one interface at a time.

Great yes we all will have to chip in and start removing these, i will try
doing few after new year

Am sure Andy can chip in as well :)

> This is what I see:
> 
> arnd@wuerfel:~/arm-soc$ for i in dma_request_slave_channel_reason dma_request_slave_channel dma_request_slave_channel_compat dma_request_channel  ; do echo `git grep -wl $i drivers/  | grep -v drivers/dma | wc -l`\      $i ; done
> 14      dma_request_slave_channel_reason
> 27      dma_request_slave_channel
> 25      dma_request_slave_channel_compat
> 34      dma_request_channel
> 
> I would probably leave the users of dma_request_channel() while converting
> the others, as that is still used by all the platforms that don't use any DT
> support.
> 
> Changing dma_request_slave_channel_reason and dma_request_slave_channel is
> trivial, we can probably use coccinelle for that, as it does not require
> any platform changes. That brings us to the users of
> dma_request_slave_channel_compat, which currently includes these files:
> 
> $ git grep -wl dma_request_slave_channel_compat drivers/ata/pata_pxa.c
> drivers/crypto/atmel-aes.c
> drivers/crypto/atmel-sha.c
> drivers/crypto/atmel-tdes.c
> drivers/crypto/omap-aes.c
> drivers/crypto/omap-des.c
> drivers/crypto/omap-sham.c
> drivers/media/platform/omap3isp/isphist.c
> drivers/mmc/host/davinci_mmc.c
> drivers/mmc/host/omap.c
> drivers/mmc/host/omap_hsmmc.c
> drivers/mmc/host/pxamci.c
> drivers/mmc/host/s3cmci.c
> drivers/mmc/host/tmio_mmc_dma.c
> drivers/mtd/nand/pxa3xx_nand.c
> drivers/net/ethernet/smsc/smc91x.c
> drivers/net/irda/pxaficp_ir.c
> drivers/spi/spi-omap2-mcspi.c
> drivers/spi/spi-pxa2xx-dma.c
> drivers/spi/spi-rspi.c
> drivers/spi/spi-s3c64xx.c
> drivers/spi/spi-sh-msiof.c
> drivers/tty/serial/8250/8250_dma.c
> drivers/tty/serial/samsung.c
> drivers/tty/serial/sh-sci.c
> include/linux/dmaengine.h
> 
> In other words: arch/avr32 and arch/sh along with omap1, omap2, davinci, pxa, and s3c
> in terms of ARM platforms.
> 
> 	Arnd

-- 
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#1281517 — Re: [RFC v02 00/15] dmaengine: New 'universal' API for requesting channel

On Wednesday 02 December 2015 10:22:09 Vinod Koul wrote:
> > 
> > > > This legacy mode needs changes in platform code, in dmaengine drivers and
> > > > finally the dmaengine user drivers can be converted:
> > > 
> > > Are you marking the current APIs as dericated in the end of this series
> > 
> > I think we practically stopped marking things as deprecated in general.
> > Per Linus decree, whenever we want to get rid of something, we should
> > instead change all users in tree and then remove the API, expecting
> > driver maintainers to do something just because you marked it as deprecated
> > often doesn't work.
> 
> Yes but while we do conversion we don't know if new users get added which use
> old API..

We probably don't need to worry about new users of dma_request_channel(),
as we don't add new ARM platforms without DT, and other architectures
don't add a lot of new platforms. Similarly, I don't expect a whole lot
of dma_request_slave_channel_compat() users, because the conversion from
board files to DT based booting has slowed down a lot after most of the
actively maintained platforms are done with it.

If you do a one-line patch to add dma_request_chan() as an alias for
dma_request_slave_channel_reason() now, we can probably convert most
users of dma_request_slave_channel() and dma_request_slave_channel_reason()
to dma_request_chan() in the next merge window and do a patch to
replace the few remaining ones and remove the API one merge window later.

If wewant to stage out the conversion of the
dma_request_slave_channel_compat() and dma_request_channel() similarly,
it would be good to have all the interface changes for the dmaengine
core basically in place, so we can start to convert the platforms
independently for the 4.5 merge window without having a dependency on
dmaengine patches. It's probably best to not convert a slave driver
away from dma_request_channel() until the dma map has been created
for all platforms using that driver, again to avoid having too many
dependencies.

	Arnd
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#1281740

On 12/01/2015 10:17 PM, Arnd Bergmann wrote:
> On Tuesday 01 December 2015 22:29:54 Vinod Koul wrote:
>> On Mon, Nov 30, 2015 at 03:45:30PM +0200, Peter Ujfalusi wrote:
>>> channel via DT, ACPI or in case if the kernel booted in non DT/ACPI mode
>>> it will use a filter lookup table and retrieves the needed information from
>>> the dma_filter_map provided by the DMA drivers.
>>
>> That sounds right, for the third case would the arch, driver or someone else
>> configure this?
> 
> The typical case is for the configuration to be defined in arch or platform
> code and passed down to the dmaengine driver.
> 
> I just noticed that the text above (and probably the code too) should
> be changed so we always fall back to this. There are cases where the
> platform is booted with DT in principle, but the DMA engine does not
> (yet) use DT and still wants to be converted. I think we can easily
> handle that case by always trying this if the other methods fail.

Yes, it was intentional actually to not fall back to legacy lookup. With the
dma_request_slave_channel_compat() I have had cases when the DT binding was
not correct - or actually when trying to get deferred working that the code
would fall back to legacy mode and it got me a channel which is not usable.
I did not know that we have platforms booting in DT but the dma binding is not
working so it uses other method to get channel.
I think, if we allow the fall back within dma_request_chan() it would not
cause the same issue as the dma_request_slave_channel_compat() did as long as
we are not providing the lookup table on DT booted cases when the DMA binding
is working correctly.
Let me see the flow, but I think it is doable.

-- 
Péter
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