ARM: PXA27x: fix workaround for AC97 reset

PATCH New Igor Grinberg 3 participants 7 messages Jan 6, 2013 – Jan 7, 2013

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Arm (32-bit) Arm sub-architectures PXA2xx/PXA3xx support

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Igor Grinberg

author

2013-01-06 11:12 UTC #0 lore raw

PATCH 1/1 ARM: PXA27x: fix workaround for AC97 reset

Fix the workaround to a hardware bug in the AC97 controller of PXA27x. A bug in the controller's warm reset functionality requires that the MFP used by the controller as the AC97_RESET_n line be temporarily reconfigured as a GPIO (AF0) and manually held high for the duration of the warm reset cycle.

The workaround was broken long ago by commit fb1bf8cd
([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset()). The commit above changed the original workaround code in a way that changed the MFP to AF0 (GPIO), but forgot to drive the GPIO high output. This way, the GPIO state was left input (and undriven) and only worked for boards with external pullup on the line.

Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF2 and GPDR - input) in case of reset deassert.

Reported-by Mike Dunn <[email protected]>

Signed-off-by Igor Grinberg <[email protected]>

Cc Robert Jarzmik <[email protected]>

Cc Eric Miao <[email protected]>

Cc stable at vger.kernel.org

---
Mike, this should work and without the GPIO not requested warning. Can you test this, please?

 arch/arm/mach-pxa/devices.c |   13 ++++++++++++-
 arch/arm/mach-pxa/pxa27x.c  |    5 +++++
 2 files changed, 17 insertions(+), 1 deletions(-)

arch/arm/mach-pxa/devices.c +12 -1

index daa86d3..eaa7282 100644
@@ -5,6 +5,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/spi/pxa2xx_spi.h>
 #include <linux/i2c/pxa-i2c.h>
+#include <linux/gpio.h>
 
 #include <mach/udc.h>
 #include <linux/platform_data/usb-pxa3xx-ulpi.h>

@@ -488,7 +489,17 @@ struct platform_device pxa_device_ac97 = {
 
 void __init pxa_set_ac97_info(pxa2xx_audio_ops_t *ops)
 {
-	pxa_register_device(&pxa_device_ac97, ops);
+	int err = 0;
+
+	if (ops && gpio_is_valid(ops->reset_gpio)) {
+		err = gpio_request_one(ops->reset_gpio, GPIOF_IN, "ac97 rst");
+		if (err)
+			pr_err("%s: Failed requesting GPIO%d (ac97 rst): %d",
+			       __func__, ops->reset_gpio, err);
+	}
+
+	if (!err)
+		pxa_register_device(&pxa_device_ac97, ops);
 }
 
 #ifdef CONFIG_PXA25x

arch/arm/mach-pxa/pxa27x.c +5 -0

index 8047ee0..bb7e7c3 100644
@@ -62,6 +62,11 @@ void pxa27x_assert_ac97reset(int reset_gpio, int on)
 	if (reset_gpio == 95)
 		pxa2xx_mfp_config(on ? &ac97_reset_config[2] :
 				       &ac97_reset_config[3], 1);
+
+	if (on)
+		gpio_direction_output(reset_gpio, 1);
+	else	/* to be on the safe side, return the GPDR to input */
+		gpio_direction_input(reset_gpio);
 }
 EXPORT_SYMBOL_GPL(pxa27x_assert_ac97reset);

Signature · 1 line

1.7.3.4

Robert Jarzmik

maintainer NAK

2013-01-06 14:07 UTC #1 lore raw

PATCH 1/1 ARM: PXA27x: fix workaround for AC97 reset

Quoted 13 lines · Igor Grinberg

Fix the workaround to a hardware bug in the AC97 controller of PXA27x. A bug in the controller's warm reset functionality requires that the MFP used by the controller as the AC97_RESET_n line be temporarily reconfigured as a GPIO (AF0) and manually held high for the duration of the warm reset cycle.
The workaround was broken long ago by commit fb1bf8cd
([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset()). The commit above changed the original workaround code in a way that changed the MFP to AF0 (GPIO), but forgot to drive the GPIO high output. This way, the GPIO state was left input (and undriven) and only worked for boards with external pullup on the line.

Quoted 3 lines

Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF2 and GPDR - input) in case of reset deassert.

NAK.
If you return GPIO95 to AF-input, the GPIO95 will be "KP_DKIN<2>", ie. you'll map a keyboard input to a AC97 reset.
As I said in a mail before, don't put a AC97 reset line as an input pin, this is not a sensible patch.

Cheers.

--
Robert

Igor Grinberg

author

2013-01-06 16:24 UTC #2 lore raw

PATCH 1/1 ARM: PXA27x: fix workaround for AC97 reset

Quoted 15 lines · Robert Jarzmik

Quoted 13 lines · Igor Grinberg
Fix the workaround to a hardware bug in the AC97 controller of PXA27x. A bug in the controller's warm reset functionality requires that the MFP used by the controller as the AC97_RESET_n line be temporarily reconfigured as a GPIO (AF0) and manually held high for the duration of the warm reset cycle.
The workaround was broken long ago by commit fb1bf8cd
([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset()). The commit above changed the original workaround code in a way that changed the MFP to AF0 (GPIO), but forgot to drive the GPIO high output. This way, the GPIO state was left input (and undriven) and only worked for boards with external pullup on the line.

Quoted 7 lines

Quoted 3 lines
Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF2 and GPDR - input) in case of reset deassert.
NAK.
If you return GPIO95 to AF-input, the GPIO95 will be "KP_DKIN<2>", ie. you'll map a keyboard input to a AC97 reset.

I'm sorry, I don't understand what do you mean by "AF-input"? For GPIO95 AF1 means AC97_nRESET and GPDR settings should not meter at all. So setting GPDR for GPIO95/113 to input is only a safety measure.

Quoted 2 lines

As I said in a mail before, don't put a AC97 reset line as an input pin, this is not a sensible patch.

Hmmm... I've opened the PXA27x dev manual once again in several years. Ok. I was mislead by all the newer SoC where direction pins do not count unless the MFP in AF-GPIO. As I've remembered now, it is not true for PXA27x.

This is what the manual says:
"Each pin can be programmed as an output, an input, or as bidirectional for certain alternate functions (that override the value programmed in the GPIO direction registers)."

So, you're right and GPDR does meter for AC97_nRESET. I'll send a v2.

Thanks!

Signature · 2 lines

Regards,
Igor.

Igor Grinberg

author

2013-01-06 16:48 UTC #3 lore raw

PATCH v2 1/1 ARM: PXA27x: fix workaround for AC97 reset

In reply to Robert Jarzmik

Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF1 - for GPIO95 and AF2 - for GPIO113) in case of reset deassert.

Reported-by Mike Dunn <[email protected]>

Signed-off-by Igor Grinberg <[email protected]>

Cc Mike Dunn <[email protected]>

Cc Robert Jarzmik <[email protected]>

Cc Eric Miao <[email protected]>

Cc stable at vger.kernel.org

---
v2: Do not change the GPDR to input on reset deassert, as AC97
controller will not drive it (thanks Robert). Also, this time really send to Mike.

Mike, Robert, can you test this one on boards with GPIO113 and GPIO95? Thanks!

 arch/arm/mach-pxa/devices.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

arch/arm/mach-pxa/devices.c +13 -1

index daa86d3..03db2ce 100644
@@ -5,6 +5,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/spi/pxa2xx_spi.h>
 #include <linux/i2c/pxa-i2c.h>
+#include <linux/gpio.h>
 
 #include <mach/udc.h>
 #include <linux/platform_data/usb-pxa3xx-ulpi.h>

@@ -488,7 +489,18 @@ struct platform_device pxa_device_ac97 = {
 
 void __init pxa_set_ac97_info(pxa2xx_audio_ops_t *ops)
 {
-	pxa_register_device(&pxa_device_ac97, ops);
+	int err = 0;
+
+	if (ops && gpio_is_valid(ops->reset_gpio)) {
+		err = gpio_request_one(ops->reset_gpio, GPIOF_INIT_HIGH,
+				       "ac97 rst");
+		if (err)
+			pr_err("%s: Failed requesting GPIO%d (ac97 rst): %d",
+			       __func__, ops->reset_gpio, err);
+	}
+
+	if (!err)
+		pxa_register_device(&pxa_device_ac97, ops);
 }
 
 #ifdef CONFIG_PXA25x

Signature · 1 line

1.7.3.4

Mike Dunn

2013-01-06 19:26 UTC #4 lore raw

PATCH v2 1/1 ARM: PXA27x: fix workaround for AC97 reset

Whoops, I just submitted some patches that clash with this. Sorry, didn't see this one. I'll test this, and will resubmit my patches to work with this one if necessary. Your code placement is probably better.

Thanks,
Mike

Quoted 66 lines · Igor Grinberg

Fix the workaround to a hardware bug in the AC97 controller of PXA27x. A bug in the controller's warm reset functionality requires that the MFP used by the controller as the AC97_RESET_n line be temporarily reconfigured as a GPIO (AF0) and manually held high for the duration of the warm reset cycle.
The workaround was broken long ago by commit fb1bf8cd
([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset()). The commit above changed the original workaround code in a way that changed the MFP to AF0 (GPIO), but forgot to drive the GPIO high output. This way, the GPIO state was left input (and undriven) and only worked for boards with external pullup on the line.
Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF1 - for GPIO95 and AF2 - for GPIO113) in case of reset deassert.
Reported-by Mike Dunn <[email protected]>
Signed-off-by Igor Grinberg <[email protected]>
Cc Mike Dunn <[email protected]>
Cc Robert Jarzmik <[email protected]>
Cc Eric Miao <[email protected]>
Cc stable at vger.kernel.org
---
v2: Do not change the GPDR to input on reset deassert, as AC97
controller will not drive it (thanks Robert). Also, this time really send to Mike.
Mike, Robert, can you test this one on boards with GPIO113 and GPIO95? Thanks!
 arch/arm/mach-pxa/devices.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)
arch/arm/mach-pxa/devices.c +13 -1
index daa86d3..03db2ce 100644
@@ -5,6 +5,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/spi/pxa2xx_spi.h>
 #include <linux/i2c/pxa-i2c.h>
+#include <linux/gpio.h>
 
 #include <mach/udc.h>
 #include <linux/platform_data/usb-pxa3xx-ulpi.h>
@@ -488,7 +489,18 @@ struct platform_device pxa_device_ac97 = {
 
 void __init pxa_set_ac97_info(pxa2xx_audio_ops_t *ops)
 {
-	pxa_register_device(&pxa_device_ac97, ops);
+	int err = 0;
+
+	if (ops && gpio_is_valid(ops->reset_gpio)) {
+		err = gpio_request_one(ops->reset_gpio, GPIOF_INIT_HIGH,
+				       "ac97 rst");
+		if (err)
+			pr_err("%s: Failed requesting GPIO%d (ac97 rst): %d",
+			       __func__, ops->reset_gpio, err);
+	}
+
+	if (!err)
+		pxa_register_device(&pxa_device_ac97, ops);
 }
 
 #ifdef CONFIG_PXA25x

Mike Dunn

2013-01-06 22:19 UTC #5 lore raw

PATCH v2 1/1 ARM: PXA27x: fix workaround for AC97 reset

In reply to Igor Grinberg

Quoted 13 lines · Igor Grinberg

Fix the workaround to a hardware bug in the AC97 controller of PXA27x. A bug in the controller's warm reset functionality requires that the MFP used by the controller as the AC97_RESET_n line be temporarily reconfigured as a GPIO (AF0) and manually held high for the duration of the warm reset cycle.
The workaround was broken long ago by commit fb1bf8cd
([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset()). The commit above changed the original workaround code in a way that changed the MFP to AF0 (GPIO), but forgot to drive the GPIO high output. This way, the GPIO state was left input (and undriven) and only worked for boards with external pullup on the line.

Quoted 3 lines

Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF1 - for GPIO95 and AF2 - for GPIO113) in case of reset deassert.

Hi Igor,

I pulled patches 2, 3, and 4 from my patch set (patch #1 fixes an unrelated problem with ac97 cold reset) and replaced it with this, and warm reset works. My pxa270 uses gpio 95 for reset, BTW. I don't have a platform that uses 113.

Honestly, I don't understand why it works :) The pxa27x_assert_ac97reset() function calls pxa2xx_mfp_config() with an input direction configuration when it switches to gpio (AF0), so I don't see how the line remains an output driven high. I think you tried to explain that in the email exchange, but I'm still confused. I'm looking at __mfp_config_gpio(), and it looks like it's setting the GPDR register.

[..]

Quoted 9 lines

void __init pxa_set_ac97_info(pxa2xx_audio_ops_t *ops) {

arch/arm/mach-pxa/devices.c +5 -1

-	pxa_register_device(&pxa_device_ac97, ops);
+	int err = 0;
+
+	if (ops && gpio_is_valid(ops->reset_gpio)) {
+		err = gpio_request_one(ops->reset_gpio, GPIOF_INIT_HIGH,
+				       "ac97 rst");

arch/arm/mach-pxa/devices.c struct platform_device pxa_device_ac97 = { · line 506

Quoted 10 lines

arch/arm/mach-pxa/devices.c +7 -0

+		if (err)
+			pr_err("%s: Failed requesting GPIO%d (ac97 rst): %d",
+			       __func__, ops->reset_gpio, err);
+	}
+
+	if (!err)
+		pxa_register_device(&pxa_device_ac97, ops);
 }
 
 #ifdef CONFIG_PXA25x

On further thought, I'm not sure about doing this here. This file is for all pxa's, no? The gpio only needs to be obtained for pxa270. And even in that case, the ac97 controller peripheral may not be used if no codec is attached, in which case the pins are free to be used for any kind of gpio. It might be better to have the ac97 driver request the gpio.

And a more general complaint: the functionality is very obscure. (Heck, I still can't figure it out! :)

Thanks Igor,
Mike

Igor Grinberg

author

2013-01-07 09:13 UTC #6 lore raw

PATCH v2 1/1 ARM: PXA27x: fix workaround for AC97 reset

Quoted 19 lines · Mike Dunn

Quoted 13 lines · Igor Grinberg
Fix the workaround to a hardware bug in the AC97 controller of PXA27x. A bug in the controller's warm reset functionality requires that the MFP used by the controller as the AC97_RESET_n line be temporarily reconfigured as a GPIO (AF0) and manually held high for the duration of the warm reset cycle.
The workaround was broken long ago by commit fb1bf8cd
([ARM] pxa: introduce processor specific pxa27x_assert_ac97reset()). The commit above changed the original workaround code in a way that changed the MFP to AF0 (GPIO), but forgot to drive the GPIO high output. This way, the GPIO state was left input (and undriven) and only worked for boards with external pullup on the line.
Quoted 3 lines
Fix the above breakage by actually configurring the GPIO for output high in case of reset assert and returning it to default state (AF1 - for GPIO95 and AF2 - for GPIO113) in case of reset deassert.

Quoted 5 lines

Hi Igor,
I pulled patches 2, 3, and 4 from my patch set (patch #1 fixes an unrelated problem with ac97 cold reset) and replaced it with this, and warm reset works. My pxa270 uses gpio 95 for reset, BTW. I don't have a platform that uses 113.

Thanks!

Quoted 7 lines

Honestly, I don't understand why it works :) The pxa27x_assert_ac97reset() function calls pxa2xx_mfp_config() with an input direction configuration when it switches to gpio (AF0), so I don't see how the line remains an output driven high. I think you tried to explain that in the email exchange, but I'm still confused. I'm looking at __mfp_config_gpio(), and it looks like it's setting the GPDR register.

Yeah, I see your concern now...
Probably, we still need a combination of both: like in v1 of my patch, just without changing the direction to input.

Quoted 22 lines

[..]

Quoted 18 lines

void __init pxa_set_ac97_info(pxa2xx_audio_ops_t *ops) {

arch/arm/mach-pxa/devices.c +12 -1

-	pxa_register_device(&pxa_device_ac97, ops);
+	int err = 0;
+
+	if (ops && gpio_is_valid(ops->reset_gpio)) {
+		err = gpio_request_one(ops->reset_gpio, GPIOF_INIT_HIGH,
+				       "ac97 rst");
+		if (err)
+			pr_err("%s: Failed requesting GPIO%d (ac97 rst): %d",
+			       __func__, ops->reset_gpio, err);
+	}
+
+	if (!err)
+		pxa_register_device(&pxa_device_ac97, ops);
 }

Quoted 5 lines

Quoted 1 line
#ifdef CONFIG_PXA25x
On further thought, I'm not sure about doing this here. This file is for all pxa's, no? The gpio only needs to be obtained for pxa270.

The only problem I can see here, is that the ops->reset_gpio
may be uninitialized ( = 0 ) and that will be a problem as 0 is a valid GPIO, so there are several options here:
1) Change all the users of pxa_set_ac97_info() that provide non-NULL ops pointer to initialize the reset_gpio to -EINVAL (preferable)
2) We can check cpu_is_pxa27x().
3) We can check that provided GPIO is 95 or 113.

Quoted 3 lines

And even in that
case, the ac97 controller peripheral may not be used if no codec is attached, in which case the pins are free to be used for any kind of gpio.

In such case you should not call pxa_set_ac97_info(), right?

Quoted 2 lines

It might be
better to have the ac97 driver request the gpio.

Thought about that, but this means we request the GPIO in the driver but configure it (gpio_direction_out()) in the arch code - this is a bit awkward.

I would go for implementing 1), unless we have no problem requesting the GPIO in the driver and driving it in the arch code...

Signature · 2 lines

Regards,
Igor.