serial: 8250_dw: Enable DMA support with ACPI

With ACPI 5.0 we can use the FixedDMA Resource Descriptor to
extract the needed information for DMA support.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index f6eeff02dced..ceacf5e36f2e 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -27,6 +27,8 @@
 #include <linux/slab.h>
 #include <linux/acpi.h>
 
+#include "8250.h"
+
 /* Offsets for the DesignWare specific registers */
 #define DW_UART_USR     0x1f /* UART Status Register */
 #define DW_UART_CPR     0xf4 /* Component Parameter Register */
@@ -143,9 +145,64 @@ static int dw8250_probe_of(struct uart_port *p)
         return 0;
 }
 
+static bool dw8250_acpi_dma_filter(struct dma_chan *chan, void *parm)
+{
+        return chan->chan_id == *(int *)parm;
+}
+
+static acpi_status
+dw8250_acpi_walk_resource(struct acpi_resource *res, void *data)
+{
+        struct uart_port                *p = data;
+        struct uart_8250_port           *port;
+        struct uart_8250_dma            *dma;
+        struct acpi_resource_fixed_dma  *fixed_dma;
+        struct dma_slave_config         *slave;
+
+        port = container_of(p, struct uart_8250_port, port);
+
+        switch (res->type) {
+        case ACPI_RESOURCE_TYPE_FIXED_DMA:
+                fixed_dma = &res->data.fixed_dma;
+
+                /* TX comes first */
+                if (!port->dma) {
+                        dma = devm_kzalloc(p->dev, sizeof(*dma), GFP_KERNEL);
+                        if (!dma)
+                                return AE_NO_MEMORY;
+
+                        port->dma = dma;
+                        slave = &dma->txconf;
+
+                        slave->direction        = DMA_MEM_TO_DEV;
+                        slave->dst_addr_width   = DMA_SLAVE_BUSWIDTH_1_BYTE;
+                        slave->slave_id         = fixed_dma->request_lines;
+
+                        dma->tx_chan_id         = fixed_dma->channels;
+                        dma->tx_param           = &dma->tx_chan_id;
+                        dma->fn                 = dw8250_acpi_dma_filter;
+                } else {
+                        dma = port->dma;
+                        slave = &dma->rxconf;
+
+                        slave->direction        = DMA_DEV_TO_MEM;
+                        slave->src_addr_width   = DMA_SLAVE_BUSWIDTH_1_BYTE;
+                        slave->slave_id         = fixed_dma->request_lines;
+
+                        dma->rx_chan_id         = fixed_dma->channels;
+                        dma->rx_param           = &dma->rx_chan_id;
+                }
+
+                break;
+        }
+
+        return AE_OK;
+}
+
 static int dw8250_probe_acpi(struct uart_port *p)
 {
         const struct acpi_device_id *id;
+        acpi_status status;
         u32 reg;
 
         id = acpi_match_device(p->dev->driver->acpi_match_table, p->dev);
@@ -158,6 +215,14 @@ static int dw8250_probe_acpi(struct uart_port *p)
         p->regshift = 2;
         p->uartclk = (unsigned int)id->driver_data;
 
+        status = acpi_walk_resources(ACPI_HANDLE(p->dev), METHOD_NAME__CRS,
+                                     dw8250_acpi_walk_resource, p);
+        if (ACPI_FAILURE(status)) {
+                dev_err_ratelimited(p->dev, "%s failed \"%s\"\n", __func__,
+                                    acpi_format_exception(status));
+                return -ENODEV;
+        }
+
         /* Fix Haswell issue where the clocks do not get enabled */
         if (!strcmp(id->id, "INT33C4") || !strcmp(id->id, "INT33C5")) {
                 reg = readl(p->membase + LPSS_PRV_CLOCK_PARAMS);