Граф коммитов

31 Коммитов

Автор SHA1 Сообщение Дата
Cai Huoqing 07c609cc98 dmaengine: sa11x0: Mark PM functions as __maybe_unused
Without CONFIG_PM_SLEEP, the runtime suspend/resume functions
are unused, producing a warning:

../drivers/dma/sa11x0-dma.c:1042:12: error: 'sa11x0_dma_resume' defined but not used
../drivers/dma/sa11x0-dma.c:1004:12: error: 'sa11x0_dma_suspend' defined but not used

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20211026020508.550-1-caihuoqing@baidu.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2021-10-26 10:55:07 +05:30
Cai Huoqing 7789e3464c dmaengine: sa11x0: Make use of the helper macro SET_NOIRQ_SYSTEM_SLEEP_PM_OPS()
Use the helper macro SET_NOIRQ_SYSTEM_SLEEP_PM_OPS() instead of the
verbose operators ".suspend_noirq /.resume_noirq/.freeze_noirq/
.thaw_noirq/.poweroff_noirq/.restore_noirq", because the
SET_NOIRQ_SYSTEM_SLEEP_PM_OPS() is a nice helper macro that could
be brought in to make code a little clearer, a little more concise.

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20210828090117.1814-1-caihuoqing@baidu.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2021-10-25 12:09:15 +05:30
Allen Pais 8a536883e0 dmaengine: sa11x0: convert tasklets to use new tasklet_setup() API
In preparation for unconditionally passing the
struct tasklet_struct pointer to all tasklet
callbacks, switch to using the new tasklet_setup()
and from_tasklet() to pass the tasklet pointer explicitly.

Signed-off-by: Romain Perier <romain.perier@gmail.com>
Signed-off-by: Allen Pais <allen.lkml@gmail.com>
Link: https://lore.kernel.org/r/20200831103542.305571-24-allen.lkml@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2020-09-18 12:19:07 +05:30
Gustavo A. R. Silva bfb59d4a33 dmaengine: sa11x0: Replace zero-length array with flexible-array member
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200214171435.GA22930@embeddedor
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2020-02-19 17:48:40 +05:30
Thomas Gleixner d2912cb15b treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500
Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-19 17:09:55 +02:00
Julia Lawall de2c45314d dmaengine: sa11x0: drop useless LIST_HEAD
Drop LIST_HEAD where the variable it declares has never been
used.

The semantic patch that fixes this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier x;
@@
- LIST_HEAD(x);
  ... when != x
// </smpl>

Fixes: 4a533218fc ("dmaengine: sa11x0: Split device_control")
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2019-01-07 09:49:26 +05:30
Russell King bc822e8017 dmaengine: sa11x0: unexport sa11x0_dma_filter_fn and clean up
As we now have no users of sa11x0_dma_filter_fn() in the tree, we can
unexport this function, and remove the now unused header file.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
2018-11-11 14:54:08 +05:30
Kees Cook acafe7e302 treewide: Use struct_size() for kmalloc()-family
One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    void *entry[];
};

instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL);

This patch makes the changes for kmalloc()-family (and kvmalloc()-family)
uses. It was done via automatic conversion with manual review for the
"CHECKME" non-standard cases noted below, using the following Coccinelle
script:

// pkey_cache = kmalloc(sizeof *pkey_cache + tprops->pkey_tbl_len *
//                      sizeof *pkey_cache->table, GFP_KERNEL);
@@
identifier alloc =~ "kmalloc|kzalloc|kvmalloc|kvzalloc";
expression GFP;
identifier VAR, ELEMENT;
expression COUNT;
@@

- alloc(sizeof(*VAR) + COUNT * sizeof(*VAR->ELEMENT), GFP)
+ alloc(struct_size(VAR, ELEMENT, COUNT), GFP)

// mr = kzalloc(sizeof(*mr) + m * sizeof(mr->map[0]), GFP_KERNEL);
@@
identifier alloc =~ "kmalloc|kzalloc|kvmalloc|kvzalloc";
expression GFP;
identifier VAR, ELEMENT;
expression COUNT;
@@

- alloc(sizeof(*VAR) + COUNT * sizeof(VAR->ELEMENT[0]), GFP)
+ alloc(struct_size(VAR, ELEMENT, COUNT), GFP)

// Same pattern, but can't trivially locate the trailing element name,
// or variable name.
@@
identifier alloc =~ "kmalloc|kzalloc|kvmalloc|kvzalloc";
expression GFP;
expression SOMETHING, COUNT, ELEMENT;
@@

- alloc(sizeof(SOMETHING) + COUNT * sizeof(ELEMENT), GFP)
+ alloc(CHECKME_struct_size(&SOMETHING, ELEMENT, COUNT), GFP)

Signed-off-by: Kees Cook <keescook@chromium.org>
2018-06-06 11:15:43 -07:00
Russell King 73d2a3cef4 dmaengine: sa11x0: add DMA filters
Add DMA filters for the sa11x0 DMA channels.  This will allow us to
migrate away from directly using the DMA filter function in drivers.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2017-09-27 16:11:51 +05:30
Vinod Koul 762ff31dd4 dmaengine: sa11x0: use correct print specifiers for size_t
This driver when compiled on 64 bits gave warnings:

drivers/dma/sa11x0-dma.c:602:2: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 6 has type ‘size_t’ [-Wformat=]

We should use %zu to print 'size_t' values.

Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2016-09-26 22:29:26 +05:30
Vinod Koul 872b4af48f dmaengine: sa11x0: use correct print specifiers for u32
This driver when compiled on 64 bits gave warnings:

drivers/dma/sa11x0-dma.c:494:2: warning: format ‘%zx’ expects argument of type ‘size_t’, but argument 4 has type ‘u32’ [-Wformat=]

We should use %x to print 'u32' values.

Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2016-09-26 22:29:20 +05:30
Vinod Koul f92e934d57 dmaengine: sa11x0: use correct print specifiers for dma_addr_t
This driver when compiled on 64 bits gave warnings:

drivers/dma/sa11x0-dma.c:466:27: warning: format '%x' expects argument of type 'unsigned int', but argument 4 has type 'dma_addr_t' [-Wformat=]
drivers/dma/sa11x0-dma.c:554:31: warning: format '%x' expects argument of type 'unsigned int', but argument 5 has type 'dma_addr_t' [-Wformat=]
drivers/dma/sa11x0-dma.c:696:34: warning: format '%x' expects argument of type 'unsigned int', but argument 5 has type 'dma_addr_t' [-Wformat=]

We should use %pad to print 'dma_addr_t' values.

Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2016-09-26 22:28:42 +05:30
Dmitry Eremin-Solenikov 28591dfdd9 dmaengine: sa11x0: report slave capabilities to upper layers
Fix the following warning by initializing necessary fields in the dma_device
structure.

------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at drivers/dma/dmaengine.c:863 dma_async_device_register+0x2b4/0x4f0()
this driver doesn't support generic slave capabilities reporting
Modules linked in:
CPU: 0 PID: 1 Comm: swapper Not tainted 4.0.0-rc5+ #10
Hardware name: Sharp-Collie
[<c0105cd8>] (unwind_backtrace) from [<c0103ef8>] (show_stack+0x10/0x14)
[<c0103ef8>] (show_stack) from [<c010e9b8>] (warn_slowpath_common+0x74/0xac)
[<c010e9b8>] (warn_slowpath_common) from [<c010ea20>] (warn_slowpath_fmt+0x30/0x40)
[<c010ea20>] (warn_slowpath_fmt) from [<c02956fc>] (dma_async_device_register+0x2b4/0x4f0)
[<c02956fc>] (dma_async_device_register) from [<c0296a9c>] (sa11x0_dma_probe+0x21c/0x358)
[<c0296a9c>] (sa11x0_dma_probe) from [<c02c52c0>] (platform_drv_probe+0x30/0x94)
[<c02c52c0>] (platform_drv_probe) from [<c02c39bc>] (driver_probe_device+0x84/0x234)
[<c02c39bc>] (driver_probe_device) from [<c02c3c4c>] (__driver_attach+0x98/0x9c)
[<c02c3c4c>] (__driver_attach) from [<c02c1f9c>] (bus_for_each_dev+0x74/0xa4)
[<c02c1f9c>] (bus_for_each_dev) from [<c02c3230>] (bus_add_driver+0x13c/0x1e8)
[<c02c3230>] (bus_add_driver) from [<c02c4260>] (driver_register+0x78/0xf8)
[<c02c4260>] (driver_register) from [<c0100624>] (do_one_initcall+0x84/0x1f4)
[<c0100624>] (do_one_initcall) from [<c0700e1c>] (kernel_init_freeable+0xf8/0x1b4)
[<c0700e1c>] (kernel_init_freeable) from [<c040a920>] (kernel_init+0x8/0xf0)
[<c040a920>] (kernel_init) from [<c01013a8>] (ret_from_fork+0x14/0x2c)
---[ end trace e188b8fe0e782e75 ]---

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-04-17 23:24:35 +05:30
Vinod Koul 7595c5717f dmaengine: sa11x0: remove device_alloc_chan_resources handler
Now that device_alloc_chan_resources handler in not mandatory, remove dummy
implementations

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-03-18 22:45:49 +05:30
Maxime Ripard a0a51a64f6 dmaengine: sa11x0: Fix warning and compilation errors
The sa11x0_dma_resume conflicts between the dmaengine device_resume callback
and the dev_pm_ops resume implementation.

Also remove some unused variables at the same time.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2015-01-18 20:01:15 +05:30
Maxime Ripard 4a533218fc dmaengine: sa11x0: Split device_control
Split the device_control callback of the SA-11x0 DMA driver to make use of the
newly introduced callbacks, that will eventually be used to retrieve slave
capabilities.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-12-22 12:32:15 +05:30
Linus Torvalds e6b5be2be4 Driver core patches for 3.19-rc1
Here's the set of driver core patches for 3.19-rc1.
 
 They are dominated by the removal of the .owner field in platform
 drivers.  They touch a lot of files, but they are "simple" changes, just
 removing a line in a structure.
 
 Other than that, a few minor driver core and debugfs changes.  There are
 some ath9k patches coming in through this tree that have been acked by
 the wireless maintainers as they relied on the debugfs changes.
 
 Everything has been in linux-next for a while.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core update from Greg KH:
 "Here's the set of driver core patches for 3.19-rc1.

  They are dominated by the removal of the .owner field in platform
  drivers.  They touch a lot of files, but they are "simple" changes,
  just removing a line in a structure.

  Other than that, a few minor driver core and debugfs changes.  There
  are some ath9k patches coming in through this tree that have been
  acked by the wireless maintainers as they relied on the debugfs
  changes.

  Everything has been in linux-next for a while"

* tag 'driver-core-3.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (324 commits)
  Revert "ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries"
  fs: debugfs: add forward declaration for struct device type
  firmware class: Deletion of an unnecessary check before the function call "vunmap"
  firmware loader: fix hung task warning dump
  devcoredump: provide a one-way disable function
  device: Add dev_<level>_once variants
  ath: ath9k: use debugfs_create_devm_seqfile() helper for seq_file entries
  ath: use seq_file api for ath9k debugfs files
  debugfs: add helper function to create device related seq_file
  drivers/base: cacheinfo: remove noisy error boot message
  Revert "core: platform: add warning if driver has no owner"
  drivers: base: support cpu cache information interface to userspace via sysfs
  drivers: base: add cpu_device_create to support per-cpu devices
  topology: replace custom attribute macros with standard DEVICE_ATTR*
  cpumask: factor out show_cpumap into separate helper function
  driver core: Fix unbalanced device reference in drivers_probe
  driver core: fix race with userland in device_add()
  sysfs/kernfs: make read requests on pre-alloc files use the buffer.
  sysfs/kernfs: allow attributes to request write buffer be pre-allocated.
  fs: sysfs: return EGBIG on write if offset is larger than file size
  ...
2014-12-14 16:10:09 -08:00
Maxime Ripard 9aa7171157 dmaengine: sa11x0: Remove chancnt affectations
chanctnt is already filled by dma_async_device_register, which uses the channel
list to know how much channels there is.

Since it's already filled, we can safely remove it from the drivers' probe
function.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-11-06 11:32:45 +05:30
Wolfram Sang 55f04d7f59 dma: drop owner assignment from platform_drivers
A platform_driver does not need to set an owner, it will be populated by the
driver core.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2014-10-20 16:20:28 +02:00
Laurent Pinchart 31c1e5a135 dmaengine: Remove the context argument to the prep_dma_cyclic operation
The argument is always set to NULL and never used. Remove it.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-08-04 13:41:50 +05:30
Arnd Bergmann fbeb91fe8e dmaengine: sa11x0: remove broken #ifdef
The sa11x0_dma_pm_ops unconditionally reference sa11x0_dma_resume
and sa11x0_dma_suspend, which currently breaks if CONFIG_PM_SLEEP
is disabled.

There is probably a better way to remove the reference in this
case, but the safe choice is to have the suspend/resume code always
built in the driver.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: dmaengine@vger.kernel.org
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2014-05-21 11:40:49 +05:30
Vinod Koul fdebb7681c dmaengine: sa11x0: use DMA_COMPLETE for dma completion status
Acked-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
2013-10-25 11:16:13 +05:30
Greg Kroah-Hartman 4bf27b8b33 Drivers: dma: remove __dev* attributes.
CONFIG_HOTPLUG is going away as an option.  As a result, the __dev*
markings need to be removed.

This change removes the use of __devinit, __devexit_p, __devinitconst,
and __devexit from these drivers.

Based on patches originally written by Bill Pemberton, but redone by me
in order to handle some of the coding style issues better, by hand.

Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Viresh Kumar <viresh.linux@gmail.com>
Cc: Dan Williams <djbw@fb.com>
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Barry Song <baohua.song@csr.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Jassi Brar <jassisinghbrar@gmail.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2013-01-03 15:57:15 -08:00
Bill Pemberton 463a1f8b3c dma: remove use of __devinit
CONFIG_HOTPLUG is going away as an option so __devinit is no longer
needed.

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Cc: Li Yang <leoli@freescale.com>
Cc: Zhang Wei <zw@zh-kernel.org>
Cc: Barry Song <baohua.song@csr.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-11-28 12:42:36 -08:00
Bill Pemberton a7d6e3ec28 dma: remove use of __devexit_p
CONFIG_HOTPLUG is going away as an option so __devexit_p is no longer
needed.

Signed-off-by: Bill Pemberton <wfp5p@virginia.edu>
Acked-by: Barry Song <baohua.song@csr.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-11-28 12:41:36 -08:00
Peter Ujfalusi ec8b5e48c0 dmaengine: Pass flags via device_prep_dma_cyclic() callback
Change the parameter list of device_prep_dma_cyclic() so the DMA drivers
can receive the flags coming from clients.
This feature can be used during audio operation to disable all audio
related interrupts when the DMA_PREP_INTERRUPT is cleared from the flags.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Vinod Koul <vinod.koul@linux.intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
2012-09-22 11:12:45 -04:00
Russell King d94443256f dmaengine: sa11x0-dma: add cyclic DMA support
Add support for cyclic DMA on sa11x0 platforms.  This follows the
discussed behaviour that the callback will be called at some point
after period expires, and may coalesce multiple period expiries into
one callback (due to the tasklet behaviour.)

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2012-07-01 14:16:26 +01:00
Russell King 63fe23c34e dmaengine: sa11x0-dma: fix DMA residue support
The semantics now implemented are:

- If the cookie has completed successfully, the residue will be zero.
- If the cookie is in progress or the channel is paused, it will be the
  number of bytes yet to be transferred. [*]
- If the cookie is queued, it will be the number of bytes in the
  descriptor.

* - where this is the number of bytes yet to be transferred to/from
  RAM.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2012-07-01 14:16:25 +01:00
Russell King 50437bff7f dmaengine: split out virtual channel DMA support from sa11x0 driver
Split the virtual slave channel DMA support from the sa11x0 driver so
this code can be shared with other slave DMA engine drivers.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2012-07-01 14:15:21 +01:00
Russell King d9d5454014 ARM: sa11x0: fix build errors from DMA engine API updates
The recent merge of the sa11x0 code into mainline had silent conflicts
with further development of the DMA engine API, leading to build errors
and warnings:

drivers/net/irda/sa1100_ir.c: In function 'sa1100_irda_dma_start':
drivers/net/irda/sa1100_ir.c:151: error: too few arguments to function 'chan->device->device_prep_slave_sg'
drivers/dma/sa11x0-dma.c: In function 'sa11x0_dma_probe':
drivers/dma/sa11x0-dma.c:950: warning: assignment from incompatible pointer type

Fix these.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2012-03-30 11:46:20 +01:00
Russell King 6365bead25 DMA: sa11x0: add SA-11x0 DMA driver
Add support for the SA-11x0 DMA driver, which replaces the private
API version in arch/arm/mach-sa1100/dma.c.

We model this as a set of virtual DMA channels, one for each request
signal, and assign the virtual DMA channel to a physical DMA channel
when there is work to be done.  This allows DMA users to claim their
channels, and hold them while not in use, without affecting the
availability of the physical channels.

Another advantage over this approach, compared to the private version,
is that a channel can be reconfigured on the fly without having to
release and re-request it - which for the IrDA driver, allows us to
use DMA for SIR mode transmit without eating up three physical
channels.  As IrDA is half-duplex, we actually only need one physical
channel, and this architecture allows us to achieve that.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2012-03-07 11:32:21 +00:00