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Commit ce3f054b authored by Peter Ujfalusi's avatar Peter Ujfalusi Committed by Tony Lindgren
Browse files

omap: McBSP: Do not enable SRG in slave mode 



McBSP SRG (Sample Rate Generator) and FSG (Frame Sync
Generator) is only needed to be enabled, when McBSP
is master.
In McBSP slave mode, the SRG, and FSG can be kept disabled,
which might save some power at the end in this configuration.

Signed-off-by: default avatarPeter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: default avatarJarkko Nikula <jhnikula@gmail.com>
Signed-off-by: default avatarTony Lindgren <tony@atomide.com>
parent 813f6c58

arch/arm/plat-omap/mcbsp.c

+8 −5
Original line number Diff line number Diff line
@@ -878,7 +878,7 @@ EXPORT_SYMBOL(omap_mcbsp_free); 
void omap_mcbsp_start(unsigned int id, int tx, int rx)

{

	struct omap_mcbsp *mcbsp;

	int idle;

	int enable_srg = 0;

	u16 w;



	if (!omap_mcbsp_check_valid_id(id)) {
@@ -893,10 +893,13 @@ void omap_mcbsp_start(unsigned int id, int tx, int rx) 
	mcbsp->rx_word_length = (MCBSP_READ_CACHE(mcbsp, RCR1) >> 5) & 0x7;

	mcbsp->tx_word_length = (MCBSP_READ_CACHE(mcbsp, XCR1) >> 5) & 0x7;



	idle = !((MCBSP_READ_CACHE(mcbsp, SPCR2) |

	/* Only enable SRG, if McBSP is master */

	w = MCBSP_READ_CACHE(mcbsp, PCR0);

	if (w & (FSXM | FSRM | CLKXM | CLKRM))

		enable_srg = !((MCBSP_READ_CACHE(mcbsp, SPCR2) |

				MCBSP_READ_CACHE(mcbsp, SPCR1)) & 1);



	if (idle) {

	if (enable_srg) {

		/* Start the sample generator */

		w = MCBSP_READ_CACHE(mcbsp, SPCR2);

		MCBSP_WRITE(mcbsp, SPCR2, w | (1 << 6));
@@ -919,7 +922,7 @@ void omap_mcbsp_start(unsigned int id, int tx, int rx) 
	 */

	udelay(500);



	if (idle) {

	if (enable_srg) {

		/* Start frame sync */

		w = MCBSP_READ_CACHE(mcbsp, SPCR2);

		MCBSP_WRITE(mcbsp, SPCR2, w | (1 << 7));