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* [PATCH 6/6] ARM: PL011: add DMA burst threshold support for ST variants
@ 2010-12-22 23:10 Russell King - ARM Linux
  0 siblings, 0 replies; 2+ messages in thread
From: Russell King - ARM Linux @ 2010-12-22 23:10 UTC (permalink / raw)
  To: linux-arm-kernel

ST Micro variants has some specific dma burst threshold compensation,
which allows them to make better use of a DMA controller.  Add support
to set this up.

Based on a patch from Linus Walleij.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/serial/amba-pl011.c |   12 ++++++++++++
 include/linux/amba/serial.h |   15 +++++++++++++++
 2 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/drivers/serial/amba-pl011.c b/drivers/serial/amba-pl011.c
index 37b4cb8..ab36317 100644
--- a/drivers/serial/amba-pl011.c
+++ b/drivers/serial/amba-pl011.c
@@ -74,6 +74,7 @@ struct vendor_data {
 	unsigned int		lcrh_tx;
 	unsigned int		lcrh_rx;
 	bool			oversampling;
+	bool			dma_threshold;
 };
 
 static struct vendor_data vendor_arm = {
@@ -82,6 +83,7 @@ static struct vendor_data vendor_arm = {
 	.lcrh_tx		= UART011_LCRH,
 	.lcrh_rx		= UART011_LCRH,
 	.oversampling		= false,
+	.dma_threshold		= false,
 };
 
 static struct vendor_data vendor_st = {
@@ -90,6 +92,7 @@ static struct vendor_data vendor_st = {
 	.lcrh_tx		= ST_UART011_LCRH_TX,
 	.lcrh_rx		= ST_UART011_LCRH_RX,
 	.oversampling		= true,
+	.dma_threshold		= true,
 };
 
 /* Deals with DMA transactions */
@@ -524,6 +527,15 @@ static void pl011_dma_startup(struct uart_amba_port *uap)
 	/* Turn on DMA error (RX/TX will be enabled on demand) */
 	uap->dmacr |= UART011_DMAONERR;
 	writew_relaxed(uap->dmacr, uap->port.membase + UART011_DMACR);
+
+	/*
+	 * ST Micro variants has some specific dma burst threshold
+	 * compensation. Set this to 16 bytes, so burst will only
+	 * be issued above/below 16 bytes.
+	 */
+	if (uap->vendor->dma_threshold)
+		writew_relaxed(ST_UART011_DMAWM_RX_16 | ST_UART011_DMAWM_TX_16,
+			       uap->port.membase + ST_UART011_DMAWM);
 }
 
 static void pl011_dma_shutdown(struct uart_amba_port *uap)
diff --git a/include/linux/amba/serial.h b/include/linux/amba/serial.h
index a307ded..47c176c 100644
--- a/include/linux/amba/serial.h
+++ b/include/linux/amba/serial.h
@@ -113,6 +113,21 @@
 #define UART01x_LCRH_PEN	0x02
 #define UART01x_LCRH_BRK	0x01
 
+#define ST_UART011_DMAWM_RX_1	(0 << 3)
+#define ST_UART011_DMAWM_RX_2	(1 << 3)
+#define ST_UART011_DMAWM_RX_4	(2 << 3)
+#define ST_UART011_DMAWM_RX_8	(3 << 3)
+#define ST_UART011_DMAWM_RX_16	(4 << 3)
+#define ST_UART011_DMAWM_RX_32	(5 << 3)
+#define ST_UART011_DMAWM_RX_48	(6 << 3)
+#define ST_UART011_DMAWM_TX_1	0
+#define ST_UART011_DMAWM_TX_2	1
+#define ST_UART011_DMAWM_TX_4	2
+#define ST_UART011_DMAWM_TX_8	3
+#define ST_UART011_DMAWM_TX_16	4
+#define ST_UART011_DMAWM_TX_32	5
+#define ST_UART011_DMAWM_TX_48	6
+
 #define UART010_IIR_RTIS	0x08
 #define UART010_IIR_TIS		0x04
 #define UART010_IIR_RIS		0x02
-- 
1.6.2.5

^ permalink raw reply related	[flat|nested] 2+ messages in thread
* [PATCH 0/6] PL011 DMA support
@ 2010-12-24 10:23 Russell King - ARM Linux
  2010-12-24 10:26 ` [PATCH 6/6] ARM: PL011: add DMA burst threshold support for ST variants Russell King - ARM Linux
  0 siblings, 1 reply; 2+ messages in thread
From: Russell King - ARM Linux @ 2010-12-24 10:23 UTC (permalink / raw)
  To: linux-arm-kernel

Re-post of the previous set, but using writew() instead of writew_relaxed().
writew_relaxed() is not part of the MMIO accessor API, and so should
not be used in drivers which may be used on other architectures.

Also copying Dan for his review of the DMA engine use.

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2010-12-24 10:26 UTC | newest]

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