[PATCH] powerpc/5200: tighten up ac97 reset timing

Eric Millbrandt emillbrandt at dekaresearch.com
Sat Sep 4 01:45:22 EST 2010

Tighten up time timing around the gpio reset functionality.  Add a 200ns
delay before remuxing the pins back to ac97 to comply with the ac97 spec.
This delay ensures that sync and sdata_out are held low while reset
transitions to high.

Signed-off-by: Eric Millbrandt <emillbrandt at dekaresearch.com>

Scope shots are availible upon request.

 arch/powerpc/platforms/52xx/mpc52xx_common.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/platforms/52xx/mpc52xx_common.c b/arch/powerpc/platforms/52xx/mpc52xx_common.c
index 6e90531..79adfe7 100644
--- a/arch/powerpc/platforms/52xx/mpc52xx_common.c
+++ b/arch/powerpc/platforms/52xx/mpc52xx_common.c
@@ -326,11 +326,14 @@ int mpc5200_psc_ac97_gpio_reset(int psc_number)
        clrbits8(&wkup_gpio->wkup_dvo, reset);

        /* wait at lease 1 us */
-       udelay(2);
+       udelay(1);

        /* Deassert reset */
        setbits8(&wkup_gpio->wkup_dvo, reset);

+       /* wait at least 200ns */
+       __delay(7);
        /* Restore pin-muxing */
        out_be32(&simple_gpio->port_config, mux);


-DISCLAIMER: an automatically appended disclaimer may follow. By posting-
-to a public e-mail mailing list I hereby grant permission to distribute-
-and copy this message.-

This e-mail and the information, including any attachments, it contains are intended to be a confidential communication only to the person or entity to whom it is addressed and may contain information that is privileged. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender and destroy the original message.

Thank you.

Please consider the environment before printing this email.

More information about the Linuxppc-dev mailing list