[PATCH v5 0/2] Add `devm_dma_request_chan()` to simplify probe path in atmel-quadspi.c

[PATCH v5 0/2] Add `devm_dma_request_chan()` to simplify probe path in atmel-quadspi.c

[Bence Csókás]

The probe function of the atmel-quadspi driver got quite convoluted,
especially since the addition of SAMA7G5 support, that was forward-ported
from an older vendor kernel. To alleivate this - and similar problems in
the future - an effort was made to migrate as many functions as possible,
to their devm_ managed counterparts. Patch 1/2 adds the new
`devm_dma_request_chan()` function. Patch 2/2 then uses this APIs to
simplify the probe() function.

Change in v4:
* split PM imbalance fix [1] and DMA cleanup [this series]

Patch 2/2 is to be applied after the PM imbalance fix [1]. Patch 1/2 can
(and should) be applied immediately, to a for-6.16 branch.

[1]
https://lore.kernel.org/lkml/20250327195928.680771-2-csokas.bence@prolan.hu/

Links to previous versions:
pre-series:
https://lore.kernel.org/linux-kernel/20241222141427.819222-1-csokas.bence@prolan.hu/
https://lore.kernel.org/linux-kernel/20250114222851.1023194-1-csokas.bence@prolan.hu/
v1:
https://lore.kernel.org/linux-kernel/20250115160244.1102881-1-csokas.bence@prolan.hu/
v2:
https://lore.kernel.org/linux-kernel/20250124085221.766303-8-csokas.bence@prolan.hu/
v3:
https://lore.kernel.org/linux-kernel/20250207124802.165408-1-csokas.bence@prolan.hu/
v4:
https://lore.kernel.org/lkml/20250317135340.382532-1-csokas.bence@prolan.hu/

Bence Csókás (2):
  dma: Add devm_dma_request_chan()
  spi: atmel-quadspi: Use `devm_dma_request_chan()`

 drivers/dma/dmaengine.c     | 30 +++++++++++++++++++++++++
 drivers/spi/atmel-quadspi.c | 44 ++++++++++---------------------------
 include/linux/dmaengine.h   |  7 ++++++
 3 files changed, 48 insertions(+), 33 deletions(-)


base-commit: 70cb3b9a371fe9ff4f50cd7889763abd4ab621dc
base-tree: https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
prerequisite-patch-id: e698614397eaaf4da550babe05eea26b7ebbfe39
-- 
2.49.0

[PATCH v5 1/2] dma: Add devm_dma_request_chan()

[Bence Csókás]

Expand the arsenal of devm functions for DMA devices, this time for
requesting channels.

Signed-off-by: Bence Csókás <csokas.bence@prolan.hu>
---
 drivers/dma/dmaengine.c   | 30 ++++++++++++++++++++++++++++++
 include/linux/dmaengine.h |  7 +++++++
 2 files changed, 37 insertions(+)

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 758fcd0546d8..ca13cd39330b 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -926,6 +926,36 @@ void dma_release_channel(struct dma_chan *chan)
 }
 EXPORT_SYMBOL_GPL(dma_release_channel);
 
+static void dmaenginem_release_channel(void *chan)
+{
+	dma_release_channel(chan);
+}
+
+/**
+ * devm_dma_request_chan - try to allocate an exclusive slave channel
+ * @dev:	pointer to client device structure
+ * @name:	slave channel name
+ *
+ * Returns pointer to appropriate DMA channel on success or an error pointer.
+ *
+ * The operation is managed and will be undone on driver detach.
+ */
+
+struct dma_chan *devm_dma_request_chan(struct device *dev, const char *name)
+{
+	struct dma_chan *chan = dma_request_chan(dev, name);
+	int ret = 0;
+
+	if (!IS_ERR(chan))
+		ret = devm_add_action_or_reset(dev, dmaenginem_release_channel, chan);
+
+	if (ret)
+		return ERR_PTR(ret);
+
+	return chan;
+}
+EXPORT_SYMBOL_GPL(devm_dma_request_chan);
+
 /**
  * dmaengine_get - register interest in dma_channels
  */
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index bb146c5ac3e4..6de7c05d6bd8 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -1524,6 +1524,7 @@ struct dma_chan *__dma_request_channel(const dma_cap_mask_t *mask,
 
 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);
+struct dma_chan *devm_dma_request_chan(struct device *dev, const char *name);
 
 void dma_release_channel(struct dma_chan *chan);
 int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps);
@@ -1560,6 +1561,12 @@ static inline struct dma_chan *dma_request_chan_by_mask(
 {
 	return ERR_PTR(-ENODEV);
 }
+
+static inline struct dma_chan *devm_dma_request_chan(struct device *dev, const char *name)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline void dma_release_channel(struct dma_chan *chan)
 {
 }
-- 
2.49.0

Re: (subset) [PATCH v5 0/2] Add `devm_dma_request_chan()` to simplify probe path in atmel-quadspi.c

[Mark Brown]

On Mon, 05 May 2025 20:49:32 +0200, Bence Csókás wrote:
> The probe function of the atmel-quadspi driver got quite convoluted,
> especially since the addition of SAMA7G5 support, that was forward-ported
> from an older vendor kernel. To alleivate this - and similar problems in
> the future - an effort was made to migrate as many functions as possible,
> to their devm_ managed counterparts. Patch 1/2 adds the new
> `devm_dma_request_chan()` function. Patch 2/2 then uses this APIs to
> simplify the probe() function.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[2/2] spi: atmel-quadspi: Use `devm_dma_request_chan()`
      commit: 2555691165a0285a4617230fed859f20dcc51608

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark