[PATCH v2 12/16] misc: support for serial slots in LP-8x4x

Sergei Ianovich
2013-12-13T02:32:03Z

Serial modules (I-870xxW series) implement DCON protocol which
allows one-master-many-slaves configuration over RS-485. When
these modules are installed into the device, they could be
accessed using the 2nd PXA built-in UART port (/dev/ttySA1).
However, it seems that addresses are not processed by the modules.
So the parallel bus needs to select which slot is connected.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
---
v0..v2
* use device tree
* use devm helpers where possible

.../devicetree/bindings/misc/lp8x4x-bus.txt | 8 ++-
Documentation/misc-devices/lp8x4x_bus.txt | 15 ++++-
drivers/misc/lp8x4x_bus.c | 75 ++++++++++++++++++++--
3 files changed, 87 insertions(+), 11 deletions(-)

diff --git a/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt b/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt
index 1c87a29..61ac96e 100644
--- a/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt
+++ b/Documentation/devicetree/bindings/misc/lp8x4x-bus.txt
@@ -5,12 +5,14 @@ See Documentation/misc-devices/lp8x4x_bus.txt for details.
Required properties:
- compatible : should be "icpdas,backplane-lp8x4x"

-- reg: physical base address of the slot count register and the length
- of the memory mapped region.
+- reg: physical base addresses and region lengths of
+ * the slot count register
+ * the serial slot select register

Example:

backplane {
compatible = "icpdas,backplane-lp8x4x";
- reg = <0x17009046 0x2>;
+ reg = <0x17009046 0x2
+ 0x17009004 0x2>;
};
diff --git a/Documentation/misc-devices/lp8x4x_bus.txt b/Documentation/misc-devices/lp8x4x_bus.txt
index f5392b3..d9a069d 100644
--- a/Documentation/misc-devices/lp8x4x_bus.txt
+++ b/Documentation/misc-devices/lp8x4x_bus.txt
@@ -19,7 +19,14 @@ LP-8x4x is an ARM-based industrial computer with a custom parallel bus to
connect expansion modules with digital input/output, analog input/output,
serial, CAN and other types of ports.

-The bus is implemented by a FPGA.
+The bus is implemented by a FPGA. There are two major groups of expansion
+modules: serial and parallel.
+
+Serial modules (I-870xxW series) implement DCON protocol which allows one-
+master-many-slaves configuration over RS-485. When these modules are installed
+into the device, they could be accessed using the 2nd PXA built-in UART port
+(/dev/ttyS1). However, it seems that addresses are not processed by
+the modules. So the parallel bus needs to select which slot is connected.

SYSFS
-----
@@ -28,3 +35,9 @@ SYSFS

slot_count
RO - shows total number of expansion slots on the device
+
+active_slot
+ RW - connects the select slot for serial communications. If there
+ is a parallel module in the selected slot, it simply ignores
+ incoming packets. So it is safe to activate any available
+ slot.
diff --git a/drivers/misc/lp8x4x_bus.c b/drivers/misc/lp8x4x_bus.c
index 7119738..cffe121 100644
--- a/drivers/misc/lp8x4x_bus.c
+++ b/drivers/misc/lp8x4x_bus.c
@@ -24,6 +24,8 @@ MODULE_DESCRIPTION("ICP DAS LP-8x4x parallel bus driver");
struct lp8x4x_master {
unsigned int slot_count;
void *count_addr;
+ unsigned int active_slot;
+ void *switch_addr;
struct device dev;
};

@@ -55,8 +57,45 @@ static ssize_t slot_count_show(struct device *dev,

static DEVICE_ATTR_RO(slot_count);

+static ssize_t active_slot_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct lp8x4x_master *m = container_of(dev, struct lp8x4x_master, dev);
+
+ return sprintf(buf, "%u\n", m->active_slot);
+}
+
+static ssize_t active_slot_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct lp8x4x_master *m = container_of(dev, struct lp8x4x_master, dev);
+ unsigned int active_slot = 0;
+ int err;
+
+ if (!buf)
+ return count;
+ if (0 == count)
+ return count;
+
+ err = kstrtouint(buf, 10, &active_slot);
+ if (err != 0 || !active_slot || active_slot > m->slot_count) {
+ dev_err(dev, "slot number is out of range 1..%u\n",
+ m->slot_count);
+ return count;
+ }
+
+ m->active_slot = active_slot;
+
+ iowrite8((1 << (m->active_slot - 1)) ^ 0xff, m->switch_addr);
+
+ return count;
+}
+
+static DEVICE_ATTR_RW(active_slot);
+
static struct attribute *master_dev_attrs[] = {
&dev_attr_slot_count.attr,
+ &dev_attr_active_slot.attr,
NULL,
};
ATTRIBUTE_GROUPS(master_dev);
@@ -69,6 +108,9 @@ static void devm_lp8x4x_bus_release(struct device *dev, void *res)
dev_dbg(dev, "releasing devices\n");
device_unregister(&m->dev);
bus_unregister(&lp8x4x_bus_type);
+
+ /* Disable serial communications */
+ iowrite8(0xff, m->switch_addr);
}

static int __init lp8x4x_bus_probe(struct platform_device *pdev)
@@ -90,8 +132,9 @@ static int __init lp8x4x_bus_probe(struct platform_device *pdev)

res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!res) {
+ dev_err(&pdev->dev, "Failed to get slot number address\n");
err = -ENODEV;
- goto err2;
+ goto err_free;
}

m->count_addr = devm_ioremap_resource(&pdev->dev, res);
@@ -99,7 +142,22 @@ static int __init lp8x4x_bus_probe(struct platform_device *pdev)
dev_err(&pdev->dev, "Failed to ioremap %p\n",
m->count_addr);
err = -EFAULT;
- goto err2;
+ goto err_free;
+ }
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
+ if (!res) {
+ dev_err(&pdev->dev, "Failed to get slot switch address\n");
+ err = -ENODEV;
+ goto err_free;
+ }
+
+ m->switch_addr = devm_ioremap_resource(&pdev->dev, res);
+ if (!m->switch_addr) {
+ dev_err(&pdev->dev, "Failed to ioremap %p\n",
+ m->switch_addr);
+ err = -EFAULT;
+ goto err_free;
}

m->slot_count = ioread8(m->count_addr);
@@ -113,15 +171,18 @@ static int __init lp8x4x_bus_probe(struct platform_device *pdev)
default:
dev_err(&pdev->dev, "unexpected slot number(%u)",
m->slot_count);
- goto err2;
+ goto err_free;
};

dev_info(&pdev->dev, "found bus with up to %u slots\n", m->slot_count);

+ /* Disable serial communications until explicitly enabled */
+ iowrite8(0xff, m->switch_addr);
+
err = bus_register(&lp8x4x_bus_type);
if (err < 0) {
dev_err(&pdev->dev, "failed to register bus type\n");
- goto err3;
+ goto err_free;
}

m->dev.bus = &lp8x4x_bus_type;
@@ -133,15 +194,15 @@ static int __init lp8x4x_bus_probe(struct platform_device *pdev)
err = device_register(&m->dev);
if (err < 0) {
dev_err(&pdev->dev, "failed to register backplane device\n");
- goto err3;
+ goto err_bus;
}

devres_add(&pdev->dev, p);
return 0;

-err3:
+err_bus:
bus_unregister(&lp8x4x_bus_type);
-err2:
+err_free:
devres_free(p);
err1:
kfree(m);
--
1.8.4.3