[PATCH 3/5] serial: pl011: use generic DMA slave configuration if possible

Arnd Bergmann
2013-01-28T21:58:18Z

With the new OF DMA binding, it is possible to completely avoid the
need for platform_data for configuring a DMA channel. In cases where the
platform has already been converted, calling dma_request_slave_channel
should get all the necessary information from the device tree.

This also adds a binding document specific to the pl011 controller,
and extends the generic primecell binding to mention "dmas" and other
common properties.

Like the patch that converts the dw_dma controller, this is completely
untested and is looking for someone to try it out.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: spi-devel-general at lists.sourceforge.net
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Vinod Koul <vinod.koul@linux.intel.com>
Cc: devicetree-discuss at lists.ozlabs.org
Cc: linux-arm-kernel at lists.infradead.org
---
.../devicetree/bindings/arm/primecell.txt | 19 ++++++-
Documentation/devicetree/bindings/serial/pl011.txt | 17 ++++++
drivers/tty/serial/amba-pl011.c | 62 +++++++++++++---------
3 files changed, 72 insertions(+), 26 deletions(-)
create mode 100644 Documentation/devicetree/bindings/serial/pl011.txt

diff --git a/Documentation/devicetree/bindings/arm/primecell.txt b/Documentation/devicetree/bindings/arm/primecell.txt
index 64fc82b..0df6aca 100644
--- a/Documentation/devicetree/bindings/arm/primecell.txt
+++ b/Documentation/devicetree/bindings/arm/primecell.txt
@@ -16,14 +16,31 @@ Optional properties:
- clocks : From common clock binding. First clock is phandle to clock for apb
pclk. Additional clocks are optional and specific to those peripherals.
- clock-names : From common clock binding. Shall be "apb_pclk" for first clock.
+- dmas : From common DMA binding. If present, refers to one or more dma channels.
+- dma-names : From common DMA binding, needs to match the 'dmas' property.
+ Devices with exactly one receive and transmit channel shall name
+ these "rx" and "tx", respectively.
+- pinctrl-<n> : Pinctrl states as described in bindings/pinctrl/pinctrl-bindings.txt
+- pinctrl-names : Names corresponding to the numbered pinctrl states
+- interrupts : one or more interrupt specifiers
+- interrupt-names : names corresponding to the interrupts properties

Example:

serial at fff36000 {
compatible = "arm,pl011", "arm,primecell";
arm,primecell-periphid = <0x00341011>;
+
clocks = <&pclk>;
clock-names = "apb_pclk";
-
+
+ dmas = <&dma-controller 4>, <&dma-controller 5>;
+ dma-names = "rx", "tx";
+
+ pinctrl-0 = <&uart0_default_mux>, <&uart0_default_mode>;
+ pinctrl-1 = <&uart0_sleep_mode>;
+ pinctrl-names = "default","sleep";
+
+ interrupts = <0 11 0x4>;
};

diff --git a/Documentation/devicetree/bindings/serial/pl011.txt b/Documentation/devicetree/bindings/serial/pl011.txt
new file mode 100644
index 0000000..5d2e840
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/pl011.txt
@@ -0,0 +1,17 @@
+* ARM AMBA Primecell PL011 serial UART
+
+Required properties:
+- compatible: must be "arm,primecell", "arm,pl011"
+- reg: exactly one register range with length 0x1000
+- interrupts: exactly one interrupt specifier
+
+Optional properties:
+- pinctrl: When present, must have one state named "sleep"
+ and one state named "default"
+- clocks: When present, must refer to exactly one clock named
+ "apb_pclk"
+- dmas: When present, may have one or two dma channels.
+ The first one must be named "rx", the second one
+ must be named "tx".
+
+See also bindings/arm/primecell.txt
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 7fca402..f9af04d 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -245,7 +245,7 @@ static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg,
}
}

-static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
+static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *uap)
{
/* DMA is the sole user of the platform data right now */
struct amba_pl011_data *plat = uap->port.dev->platform_data;
@@ -259,20 +259,25 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
struct dma_chan *chan;
dma_cap_mask_t mask;

- /* We need platform data */
- if (!plat || !plat->dma_filter) {
- dev_info(uap->port.dev, "no DMA platform data\n");
- return;
- }
+ chan = dma_request_slave_channel(dev, "tx");

- /* Try to acquire a generic DMA engine slave TX channel */
- dma_cap_zero(mask);
- dma_cap_set(DMA_SLAVE, mask);
-
- chan = dma_request_channel(mask, plat->dma_filter, plat->dma_tx_param);
if (!chan) {
- dev_err(uap->port.dev, "no TX DMA channel!\n");
- return;
+ /* We need platform data */
+ if (!plat || !plat->dma_filter) {
+ dev_info(uap->port.dev, "no DMA platform data\n");
+ return;
+ }
+
+ /* Try to acquire a generic DMA engine slave TX channel */
+ dma_cap_zero(mask);
+ dma_cap_set(DMA_SLAVE, mask);
+
+ chan = dma_request_channel(mask, plat->dma_filter,
+ plat->dma_tx_param);
+ if (!chan) {
+ dev_err(uap->port.dev, "no TX DMA channel!\n");
+ return;
+ }
}

dmaengine_slave_config(chan, &tx_conf);
@@ -282,7 +287,18 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
dma_chan_name(uap->dmatx.chan));

/* Optionally make use of an RX channel as well */
- if (plat->dma_rx_param) {
+ chan = dma_request_slave_channel(dev, "rx");
+
+ if (!chan && plat->dma_rx_param) {
+ chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);
+
+ if (!chan) {
+ dev_err(uap->port.dev, "no RX DMA channel!\n");
+ return;
+ }
+ }
+
+ if (chan) {
struct dma_slave_config rx_conf = {
.src_addr = uap->port.mapbase + UART01x_DR,
.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
@@ -291,12 +307,6 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
.device_fc = false,
};

- chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);
- if (!chan) {
- dev_err(uap->port.dev, "no RX DMA channel!\n");
- return;
- }
-
dmaengine_slave_config(chan, &rx_conf);
uap->dmarx.chan = chan;

@@ -315,6 +325,7 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
struct dma_uap {
struct list_head node;
struct uart_amba_port *uap;
+ struct device *dev;
};

static LIST_HEAD(pl011_dma_uarts);
@@ -325,7 +336,7 @@ static int __init pl011_dma_initcall(void)

list_for_each_safe(node, tmp, &pl011_dma_uarts) {
struct dma_uap *dmau = list_entry(node, struct dma_uap, node);
- pl011_dma_probe_initcall(dmau->uap);
+ pl011_dma_probe_initcall(dmau->dev, dmau->uap);
list_del(node);
kfree(dmau);
}
@@ -334,18 +345,19 @@ static int __init pl011_dma_initcall(void)

device_initcall(pl011_dma_initcall);

-static void pl011_dma_probe(struct uart_amba_port *uap)
+static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
{
struct dma_uap *dmau = kzalloc(sizeof(struct dma_uap), GFP_KERNEL);
if (dmau) {
dmau->uap = uap;
+ dmau->dev = dev;
list_add_tail(&dmau->node, &pl011_dma_uarts);
}
}
#else
-static void pl011_dma_probe(struct uart_amba_port *uap)
+static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap)
{
- pl011_dma_probe_initcall(uap);
+ pl011_dma_probe_initcall(dev, uap);
}
#endif

@@ -2023,7 +2035,7 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
uap->port.ops = &amba_pl011_pops;
uap->port.flags = UPF_BOOT_AUTOCONF;
uap->port.line = i;
- pl011_dma_probe(uap);
+ pl011_dma_probe(&dev->dev, uap);

/* Ensure interrupts from this UART are masked and cleared */
writew(0, uap->port.membase + UART011_IMSC);
--
1.8.0