serial: pl011: use generic DMA slave configuration if possible

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>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: linux-arm-kernel@lists.infradead.org

1 files changed, 37 insertions, 25 deletions

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 3ea5408fcbeb..c25b00ef9dbb 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
 
@@ -2020,7 +2032,7 @@ 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);