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omap: McBSP: Do not enable SRG in slave mode

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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: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
This commit is contained in:
Peter Ujfalusi 2010-08-31 08:11:44 +00:00 committed by Tony Lindgren
parent 813f6c5850
commit ce3f054bdd
1 changed files with 8 additions and 5 deletions
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13
arch/arm/plat-omap/mcbsp.c
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@ -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) |
MCBSP_READ_CACHE(mcbsp, SPCR1)) & 1);
/* 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));