Re: [PATCH] powerpc/5200: tighten up ac97 reset timing
On Fri, Sep 03, 2010 at 11:45:22AM -0400, Eric Millbrandt wrote: 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 emillbra...@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 */ Maybe you could fix this typo as well while you are here? - udelay(2); + udelay(1); /* Deassert reset */ setbits8(wkup_gpio-wkup_dvo, reset); + /* wait at least 200ns */ + __delay(7); ndelay(200)? + /* Restore pin-muxing */ out_be32(simple_gpio-port_config, mux); -- 1.6.3.1 -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. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev -- Pengutronix e.K. | Wolfram Sang| Industrial Linux Solutions | http://www.pengutronix.de/ | signature.asc Description: Digital signature ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
RE: [PATCH] powerpc/5200: tighten up ac97 reset timing
On Fri, 3 Sep 2010 at 12:02:09 Wolfram Sang wrote:
On Fri, Sep 03, 2010 at 11:45:22AM -0400, Eric Millbrandt wrote:
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 emillbra...@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 */
Maybe you could fix this typo as well while you are here?
Can do.
- udelay(2);
+ udelay(1);
/* Deassert reset */
setbits8(wkup_gpio-wkup_dvo, reset);
+ /* wait at least 200ns */
+ __delay(7);
ndelay(200)?
Is ndelay defined for powerpc? I was under the impression that it was
being redefined to udelay in linux/delay.h.
#ifndef ndelay
static inline void ndelay(unsigned long x)
{
udelay(DIV_ROUND_UP(x, 1000));
}
#define ndelay(x) ndelay(x)
#endif
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Re: [PATCH] powerpc/5200: tighten up ac97 reset timing
- udelay(2);
+ udelay(1);
/* Deassert reset */
setbits8(wkup_gpio-wkup_dvo, reset);
+ /* wait at least 200ns */
+ __delay(7);
ndelay(200)?
Is ndelay defined for powerpc? I was under the impression that it was
being redefined to udelay in linux/delay.h.
#ifndef ndelay
static inline void ndelay(unsigned long x)
{
udelay(DIV_ROUND_UP(x, 1000));
}
#define ndelay(x) ndelay(x)
#endif
Yes, but it is way more readable. Does the extra delay hurt? The value
of 7 looks a bit magic to me. Are you sure it will do for various clock
frequencies?
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RE: [PATCH] powerpc/5200: tighten up ac97 reset timing
On Fri, 3 Sep 2010 at 12:22:24 Wolfram Sang wrote:
- udelay(2);
+ udelay(1);
/* Deassert reset */
setbits8(wkup_gpio-wkup_dvo, reset);
+ /* wait at least 200ns */
+ __delay(7);
ndelay(200)?
Is ndelay defined for powerpc? I was under the impression that it was
being redefined to udelay in linux/delay.h.
#ifndef ndelay
static inline void ndelay(unsigned long x)
{
udelay(DIV_ROUND_UP(x, 1000));
}
#define ndelay(x) ndelay(x)
#endif
Yes, but it is way more readable. Does the extra delay hurt? The value
of 7 looks a bit magic to me. Are you sure it will do for various
clock frequencies?
The reset is happening in the gpio spinlock, so I am trying to keep busy
waiting to a minimum. The magic value of 7 calculates to *roughly* 200ns
with a system timebase of 33mhz. This timebase drives the mpc5200(b) at
its max clock speed of 400mhz, so slower frequencies should just extend the
delay, which is acceptable. If you strongly object to the use of __delay
I can change it to ndelay.
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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.
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Re: [PATCH] powerpc/5200: tighten up ac97 reset timing
Yes, but it is way more readable. Does the extra delay hurt? The value of 7 looks a bit magic to me. Are you sure it will do for various clock frequencies? The reset is happening in the gpio spinlock, so I am trying to keep busy waiting to a minimum. The magic value of 7 calculates to *roughly* 200ns with a system timebase of 33mhz. This timebase drives the mpc5200(b) at its max clock speed of 400mhz, so slower frequencies should just extend the delay, which is acceptable. If you strongly object to the use of __delay I can change it to ndelay. That might be a valid reason, dunno the details here. I'll leave the final decision for Grant. If the use of __delay is acceptable, the calculation that led to 7 should be explained, I think. -- Pengutronix e.K. | Wolfram Sang| Industrial Linux Solutions | http://www.pengutronix.de/ | signature.asc Description: Digital signature ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
