[PATCH 3.13 083/212] ARM: common: edma: Fix xbar mapping

Kamal Mostafa
2014-06-17T21:42:57Z

From: Thomas Gleixner <tglx@linutronix.de>

commit cf7eb979116c2568e8bc3b6a7269c7a359864ace upstream.

This is another great example of trainwreck engineering:

commit 2646a0e529 (ARM: edma: Add EDMA crossbar event mux support)
added support for using EDMA on peripherals which have no direct EDMA
event mapping.

The code compiles and does not explode in your face, but that's it.

1) Reading an u16 array from an u32 device tree array simply does not
work. Even if the function is named "edma_of_read_u32_to_s16_array".

It merily calls of_property_read_u16_array. So the resulting 16bit
array will have every other entry = 0.

2) The DT entry for the xbar registers related to xbar has length 0x10
instead of the real length: 0xfd0 - 0xf90 = 0x40.

Not a real problem as it does not cross a page boundary, but
wrong nevertheless.

3) But none of this matters as the mapping never happens:

After reading nonsense edma_of_read_u32_to_s16_array() invalidates
the first array entry pair, so nobody can ever notice the
braindamage by immediate explosion.

Seems the QA criteria for this code was solely not to explode when
someone adds edma-xbar-event-map entries to the DT. Goal achieved,
congratulations!

Not really helpful if someone wants to use edma on a device which
requires a xbar mapping.

Fix the issues by:

- annotating the device tree entry with "/bits/ 16" as documented in
the of_property_read_u16_array kernel doc

- make the size of the xbar register mapping correct

- invalidating the end of the array and not the start

This convoluted mess wants to be completely rewritten as there is no
point to keep the xbar_chan array memory and the iomapping of the xbar
regs around forever. Marking the xbar mapped channels as used should
be done right there.

But that's a different issue and this patch is small enough to make it
work and allows a simple backport for stable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
Documentation/devicetree/bindings/dma/ti-edma.txt | 4 +-
arch/arm/boot/dts/am33xx.dtsi | 2 +-
arch/arm/common/edma.c | 48 +++++++----------------
3 files changed, 18 insertions(+), 36 deletions(-)

diff --git a/Documentation/devicetree/bindings/dma/ti-edma.txt b/Documentation/devicetree/bindings/dma/ti-edma.txt
index 9fbbdb7..68ff213 100644
--- a/Documentation/devicetree/bindings/dma/ti-edma.txt
+++ b/Documentation/devicetree/bindings/dma/ti-edma.txt
@@ -29,6 +29,6 @@ edma: edma@49000000 {
dma-channels = <64>;
ti,edma-regions = <4>;
ti,edma-slots = <256>;
- ti,edma-xbar-event-map = <1 12
- 2 13>;
+ ti,edma-xbar-event-map = /bits/ 16 <1 12
+ 2 13>;
};
diff --git a/arch/arm/boot/dts/am33xx.dtsi b/arch/arm/boot/dts/am33xx.dtsi
index bb98f30..e86232b 100644
--- a/arch/arm/boot/dts/am33xx.dtsi
+++ b/arch/arm/boot/dts/am33xx.dtsi
@@ -114,7 +114,7 @@
compatible = "ti,edma3";
ti,hwmods = "tpcc", "tptc0", "tptc1", "tptc2";
reg = <0x49000000 0x10000>,
- <0x44e10f90 0x10>;
+ <0x44e10f90 0x40>;
interrupts = <12 13 14>;
#dma-cells = <1>;
dma-channels = <64>;
diff --git a/arch/arm/common/edma.c b/arch/arm/common/edma.c
index 41bca32..5339009 100644
--- a/arch/arm/common/edma.c
+++ b/arch/arm/common/edma.c
@@ -1423,55 +1423,38 @@ EXPORT_SYMBOL(edma_clear_event);

#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_DMADEVICES)

-static int edma_of_read_u32_to_s16_array(const struct device_node *np,
- const char *propname, s16 *out_values,
- size_t sz)
+static int edma_xbar_event_map(struct device *dev, struct device_node *node,
+ struct edma_soc_info *pdata, size_t sz)
{
- int ret;
-
- ret = of_property_read_u16_array(np, propname, out_values, sz);
- if (ret)
- return ret;
-
- /* Terminate it */
- *out_values++ = -1;
- *out_values++ = -1;
-
- return 0;
-}
-
-static int edma_xbar_event_map(struct device *dev,
- struct device_node *node,
- struct edma_soc_info *pdata, int len)
-{
- int ret, i;
+ const char pname[] = "ti,edma-xbar-event-map";
struct resource res;
void __iomem *xbar;
- const s16 (*xbar_chans)[2];
+ s16 (*xbar_chans)[2];
+ size_t nelm = sz / sizeof(s16);
u32 shift, offset, mux;
+ int ret, i;

- xbar_chans = devm_kzalloc(dev,
- len/sizeof(s16) + 2*sizeof(s16),
- GFP_KERNEL);
+ xbar_chans = devm_kzalloc(dev, (nelm + 2) * sizeof(s16), GFP_KERNEL);
if (!xbar_chans)
return -ENOMEM;

ret = of_address_to_resource(node, 1, &res);
if (ret)
- return -EIO;
+ return -ENOMEM;

xbar = devm_ioremap(dev, res.start, resource_size(&res));
if (!xbar)
return -ENOMEM;

- ret = edma_of_read_u32_to_s16_array(node,
- "ti,edma-xbar-event-map",
- (s16 *)xbar_chans,
- len/sizeof(u32));
+ ret = of_property_read_u16_array(node, pname, (u16 *)xbar_chans, nelm);
if (ret)
return -EIO;

- for (i = 0; xbar_chans[i][0] != -1; i++) {
+ /* Invalidate last entry for the other user of this mess */
+ nelm >>= 1;
+ xbar_chans[nelm][0] = xbar_chans[nelm][1] = -1;
+
+ for (i = 0; i < nelm; i++) {
shift = (xbar_chans[i][1] & 0x03) << 3;
offset = xbar_chans[i][1] & 0xfffffffc;
mux = readl(xbar + offset);
@@ -1480,8 +1463,7 @@ static int edma_xbar_event_map(struct device *dev,
writel(mux, (xbar + offset));
}

- pdata->xbar_chans = xbar_chans;
-
+ pdata->xbar_chans = (const s16 (*)[2]) xbar_chans;
return 0;
}

--
1.9.1