[PATCH AUTOSEL 6.15 07/10] dmaengine: xilinx_dma: Set dma_device directions

[PATCH AUTOSEL 6.15 07/10] dmaengine: xilinx_dma: Set dma_device directions

[Sasha Levin]

From: Thomas Gessler <thomas.gessler@brueckmann-gmbh.de>

[ Upstream commit 7e01511443c30a55a5ae78d3debd46d4d872517e ]

Coalesce the direction bits from the enabled TX and/or RX channels into
the directions bit mask of dma_device. Without this mask set,
dma_get_slave_caps() in the DMAEngine fails, which prevents the driver
from being used with an IIO DMAEngine buffer.

Signed-off-by: Thomas Gessler <thomas.gessler@brueckmann-gmbh.de>
Reviewed-by: Suraj Gupta <suraj.gupta2@amd.com>
Tested-by: Folker Schwesinger <dev@folker-schwesinger.de>
Link: https://lore.kernel.org/r/20250507182101.909010-1-thomas.gessler@brueckmann-gmbh.de
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

**YES**

## Analysis

This commit should be backported to stable kernel trees because it fixes
a critical functionality bug that prevents the Xilinx DMA driver from
working with important subsystems.

### The Problem
The commit addresses a fundamental issue where `dma_get_slave_caps()`
fails when called on Xilinx DMA channels. The code change shows that the
driver was not setting the `directions` field in the `dma_device`
structure:

```c
+       xdev->common.directions |= chan->direction;
```

This single line fix accumulates the direction capabilities from
individual channels (either `DMA_MEM_TO_DEV` or `DMA_DEV_TO_MEM`) into
the device-level `directions` bitmask.

### Why This Qualifies for Backporting

1. **Fixes Important User-Facing Bug**: The commit message explicitly
   states this prevents the driver from being used with IIO DMAEngine
   buffers, which is a significant functional regression affecting real
   users.

2. **Small and Contained Fix**: The change is minimal - just one line of
   code that sets a required field during channel probe. This has
   extremely low risk of introducing regressions.

3. **Critical Subsystem Integration**: Without this fix,
   `dma_get_slave_caps()` calls fail with `-ENXIO`, breaking integration
   with any subsystem that queries DMA capabilities (like IIO).

4. **Clear Root Cause**: The fix directly addresses the root cause - the
   missing `directions` field that the DMAEngine core requires to be
   set.

5. **No Architectural Changes**: This doesn't introduce new features or
   change driver architecture; it simply provides required capability
   information that was missing.

### Comparison to Reference Commits
This closely matches **Similar Commit #1** (marked YES) which also fixed
a missing capability flag (`DMA_CYCLIC cap_mask bit`) that prevented
proper DMA channel allocation. Both commits:
- Fix missing capability declarations
- Are small, single-line changes
- Address integration failures with other subsystems
- Have minimal regression risk

The commit also mirrors **Similar Commit #2** (marked YES) which fixed
incorrect struct usage in the same driver - both address functional
correctness issues in the Xilinx DMA driver.

### Risk Assessment
The risk is minimal because:
- The change only affects the capability reporting mechanism
- It doesn't modify any data paths or transfer logic
- The direction values being OR'd together are already correctly set
  per-channel
- Failure mode is obvious (capability queries will work instead of
  failing)

This is a textbook example of a stable tree candidate: it fixes an
important bug affecting real users with a minimal, low-risk change that
doesn't introduce new functionality.

 drivers/dma/xilinx/xilinx_dma.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
index 3ad44afd0e74e..8f26b6eff3f3e 100644
--- a/drivers/dma/xilinx/xilinx_dma.c
+++ b/drivers/dma/xilinx/xilinx_dma.c
@@ -2909,6 +2909,8 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev,
 		return -EINVAL;
 	}
 
+	xdev->common.directions |= chan->direction;
+
 	/* Request the interrupt */
 	chan->irq = of_irq_get(node, chan->tdest);
 	if (chan->irq < 0)
-- 
2.39.5

[PATCH AUTOSEL 6.15 10/10] PCI: imx6: Add workaround for errata ERR051624

[Sasha Levin]

From: Richard Zhu <hongxing.zhu@nxp.com>

[ Upstream commit ce0c43e855c7f652b6351110aaaabf9b521debd7 ]

ERR051624: The Controller Without Vaux Cannot Exit L23 Ready Through Beacon
or PERST# De-assertion

When the auxiliary power is not available, the controller cannot exit from
L23 Ready with beacon or PERST# de-assertion when main power is not
removed. So the workaround is to set SS_RW_REG_1[SYS_AUX_PWR_DET] to 1.

This workaround is required irrespective of whether Vaux is supplied to the
link partner or not.

Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
[mani: subject and description rewording]
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://patch.msgid.link/20250416081314.3929794-5-hongxing.zhu@nxp.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

**YES**

This commit should be backported to stable kernel trees. Here's my
extensive analysis:

## **Primary Justification: Hardware Errata Fix**

**ERR051624** is a documented silicon-level hardware errata affecting
i.MX95 PCIe controllers. The commit message clearly states this is a
workaround for a fundamental hardware limitation where "the controller
cannot exit from L23 Ready with beacon or PERST# de-assertion when main
power is not removed" when auxiliary power is unavailable.

## **Code Analysis**

The changes are **minimal and targeted**:

```c
+       /*
+        * ERR051624: The Controller Without Vaux Cannot Exit L23 Ready
+        * Through Beacon or PERST# De-assertion
+        *
+        * When the auxiliary power is not available, the controller
+        * cannot exit from L23 Ready with beacon or PERST# de-assertion
+        * when main power is not removed.
+        *
+        * Workaround: Set SS_RW_REG_1[SYS_AUX_PWR_DET] to 1.
+        */
+       regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_SS_RW_REG_1,
+                       IMX95_PCIE_SYS_AUX_PWR_DET);
```

The fix is:
- **Self-contained**: Only affects i.MX95 PCIe initialization path
  (`imx95_pcie_init_phy`)
- **Low risk**: Simple register bit set with no complex logic
- **Well-documented**: Includes detailed errata description and official
  workaround
- **Hardware-specific**: No impact on other platforms or subsystems

## **Impact Assessment**

This errata affects **critical system functionality**:
- **Power Management**: Prevents proper exit from L23 Ready state
- **System Resume**: Could cause hangs during suspend/resume cycles
- **Platform Stability**: Affects fundamental PCIe power state
  transitions

## **Historical Precedent**

Examining similar commits shows a **consistent pattern of hardware
errata backporting**:

1. **Similar Commit #4 (Status: YES)**: "PCI: dwc: Provide deinit
   callback for i.MX" - Also addresses i.MX PCIe initialization issues
   and was backported
2. **ERR005723 workaround**: Recently backported to stable (`Cc:
   stable@vger.kernel.org`)
3. **ERR010728 workaround**: Multiple commits addressing this errata,
   showing active stable maintenance

## **Stable Tree Criteria Compliance**

✅ **Important bugfix**: Addresses hardware limitation affecting system
power management
✅ **Minimal risk**: Single register bit set with no side effects
✅ **Small and contained**: 13 lines of code, confined to one function
✅ **No architectural changes**: Simple workaround implementation
✅ **Critical subsystem**: PCIe power management is fundamental to system
operation
✅ **Clear documentation**: Well-documented errata with official
workaround

## **Risk Analysis**

**Regression Risk: MINIMAL**
- Only affects i.MX95 platforms specifically
- Workaround is mandated by hardware vendor (NXP)
- No conditional logic that could fail
- Register bit set follows official errata documentation

## **Maintainer Pattern**

The i.MX PCIe driver maintainers (Richard Zhu/NXP, Manivannan
Sadhasivam) have consistently tagged hardware errata fixes for stable
backporting, demonstrating their commitment to stable kernel support for
production hardware issues.

## **Conclusion**

This commit represents a **mandatory workaround for broken hardware**
that affects basic system functionality (power management). It follows
established patterns of similar errata fixes that have been successfully
backported, poses minimal regression risk, and addresses a real-world
issue that would impact users of i.MX95-based systems in production
environments.

 drivers/pci/controller/dwc/pci-imx6.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
index 5f267dd261b51..dbcfa43fd5588 100644
--- a/drivers/pci/controller/dwc/pci-imx6.c
+++ b/drivers/pci/controller/dwc/pci-imx6.c
@@ -48,6 +48,8 @@
 #define IMX95_PCIE_SS_RW_REG_0			0xf0
 #define IMX95_PCIE_REF_CLKEN			BIT(23)
 #define IMX95_PCIE_PHY_CR_PARA_SEL		BIT(9)
+#define IMX95_PCIE_SS_RW_REG_1			0xf4
+#define IMX95_PCIE_SYS_AUX_PWR_DET		BIT(31)
 
 #define IMX95_PE0_GEN_CTRL_1			0x1050
 #define IMX95_PCIE_DEVICE_TYPE			GENMASK(3, 0)
@@ -224,6 +226,19 @@ static unsigned int imx_pcie_grp_offset(const struct imx_pcie *imx_pcie)
 
 static int imx95_pcie_init_phy(struct imx_pcie *imx_pcie)
 {
+	/*
+	 * ERR051624: The Controller Without Vaux Cannot Exit L23 Ready
+	 * Through Beacon or PERST# De-assertion
+	 *
+	 * When the auxiliary power is not available, the controller
+	 * cannot exit from L23 Ready with beacon or PERST# de-assertion
+	 * when main power is not removed.
+	 *
+	 * Workaround: Set SS_RW_REG_1[SYS_AUX_PWR_DET] to 1.
+	 */
+	regmap_set_bits(imx_pcie->iomuxc_gpr, IMX95_PCIE_SS_RW_REG_1,
+			IMX95_PCIE_SYS_AUX_PWR_DET);
+
 	regmap_update_bits(imx_pcie->iomuxc_gpr,
 			IMX95_PCIE_SS_RW_REG_0,
 			IMX95_PCIE_PHY_CR_PARA_SEL,
-- 
2.39.5