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Commit 38d62436 authored by Russell King's avatar Russell King
Browse files

ARM: PL011: add DMA burst threshold support for ST variants 



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.

Acked-by: default avatarLinus Walleij <linus.walleij@stericsson.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 68b65f73

drivers/serial/amba-pl011.c

+12 −0
Original line number Diff line number Diff line
@@ -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 */
@@ -527,6 +530,15 @@ 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(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(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)

include/linux/amba/serial.h

+15 −0
Original line number Diff line number Diff line
@@ -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