spi: Force CS to be in inactive state after off-mode transition

PATCH Superseded Gregory CLEMENT 3 participants 6 messages Nov 10, 2010 – Nov 11, 2010 SPI

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Gregory CLEMENT

author

2010-11-10 10:32 UTC #0 lore raw

PATCH v2 2/2 spi: Force CS to be in inactive state after off-mode transition

When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.

During the system life, I monitored the CS behavior using a oscilloscope. I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used. Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).

Signed-off-by Gregory CLEMENT <[email protected]>

---
 drivers/spi/omap2_mcspi.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

drivers/spi/omap2_mcspi.c +9 -0

index 2a651e6..938f14c 100644
@@ -1139,6 +1139,15 @@ static u8 __initdata spi4_txdma_id[] = {
 };
 #endif
 +/* When SPI wake up, CS is in wrong state: force it to unactive state*/
+static void omap2_mcspi_resume(struct spi_device *spi)
+{
+	omap2_mcspi_enable_clocks( spi_master_get_devdata(spi->master));
+	/* We need to togle CS state for OMAP take this chang in account*/
+	omap2_mcspi_force_cs(spi, 1);
+	omap2_mcspi_force_cs(spi, 0);
+	omap2_mcspi_disable_clocks( spi_master_get_devdata(spi->master));
+}
 static int __init omap2_mcspi_probe(struct platform_device *pdev)
 {
 	struct spi_master	*master;

@@ -1194,6 +1203,7 @@ static int __init omap2_mcspi_probe(struct platform_device *pdev)
 	master->transfer = omap2_mcspi_transfer;
 	master->cleanup = omap2_mcspi_cleanup;
 	master->num_chipselect = num_chipselect;
+	master->resume = omap2_mcspi_resume;
  	dev_set_drvdata(&pdev->dev, master);
 -- 1.7.0.4

Grant Likely

2010-11-10 15:57 UTC #1 lore raw

Quoted 10 lines · Gregory CLEMENT

When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.
During the system life, I monitored the CS behavior using a oscilloscope. I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used.
Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).

Sounds like a bug in the suspend/resume path of the spi_master, not the spi_device. Trying to work around it via the spi_device resume path is the wrong approach.

Quoted 34 lines

Signed-off-by Gregory CLEMENT <[email protected]>

---
 drivers/spi/omap2_mcspi.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

drivers/spi/omap2_mcspi.c +9 -0

index 2a651e6..938f14c 100644
@@ -1139,6 +1139,15 @@ static u8 __initdata spi4_txdma_id[] = {
 };
 #endif
 +/* When SPI wake up, CS is in wrong state: force it to unactive state*/
+static void omap2_mcspi_resume(struct spi_device *spi)
+{
+	omap2_mcspi_enable_clocks( spi_master_get_devdata(spi->master));
+	/* We need to togle CS state for OMAP take this chang in account*/
+	omap2_mcspi_force_cs(spi, 1);
+	omap2_mcspi_force_cs(spi, 0);
+	omap2_mcspi_disable_clocks( spi_master_get_devdata(spi->master));
+}
 static int __init omap2_mcspi_probe(struct platform_device *pdev)
 {
 	struct spi_master	*master;

@@ -1194,6 +1203,7 @@ static int __init omap2_mcspi_probe(struct
 platform_device *pdev)
 	master->transfer = omap2_mcspi_transfer;
 	master->cleanup = omap2_mcspi_cleanup;
 	master->num_chipselect = num_chipselect;
+	master->resume = omap2_mcspi_resume;
  	dev_set_drvdata(&pdev->dev, master);
 -- 1.7.0.4

Gregory CLEMENT

author

2010-11-10 16:41 UTC #2 lore raw

Quoted 12 lines · Grant Likely

Quoted 10 lines · Gregory CLEMENT
When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.
During the system life, I monitored the CS behavior using a oscilloscope. I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used.
Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).

Quoted 4 lines

Sounds like a bug in the suspend/resume path of the spi_master, not the spi_device. Trying to work around it via the spi_device resume path is the wrong approach.

OK it was not clear to me that spi_resume() and spi_suspend() were specifics to devices as these functions belong to a bus structure.

So you suggest to use the suspend/resume functions of the platform_driver structure of omap2_mcspi_driver, right?

Quoted 36 lines

Quoted 34 lines

Signed-off-by Gregory CLEMENT<[email protected]>

---
  drivers/spi/omap2_mcspi.c |   10 ++++++++++
  1 files changed, 10 insertions(+), 0 deletions(-)

drivers/spi/omap2_mcspi.c +9 -0

index 2a651e6..938f14c 100644
@@ -1139,6 +1139,15 @@ static u8 __initdata spi4_txdma_id[] = {
  };
  #endif
  +/* When SPI wake up, CS is in wrong state: force it to unactive state*/
+static void omap2_mcspi_resume(struct spi_device *spi)
+{
+	omap2_mcspi_enable_clocks( spi_master_get_devdata(spi->master));
+	/* We need to togle CS state for OMAP take this chang in account*/
+	omap2_mcspi_force_cs(spi, 1);
+	omap2_mcspi_force_cs(spi, 0);
+	omap2_mcspi_disable_clocks( spi_master_get_devdata(spi->master));
+}
  static int __init omap2_mcspi_probe(struct platform_device *pdev)
  {
  	struct spi_master	*master;

@@ -1194,6 +1203,7 @@ static int __init omap2_mcspi_probe(struct
 platform_device *pdev)
  	master->transfer = omap2_mcspi_transfer;
  	master->cleanup = omap2_mcspi_cleanup;
  	master->num_chipselect = num_chipselect;
+	master->resume = omap2_mcspi_resume;
   	dev_set_drvdata(&pdev->dev, master);
  -- 1.7.0.4

Signature · 4 lines

Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

Grant Likely

2010-11-10 17:07 UTC #3 lore raw

Quoted 20 lines · Gregory CLEMENT

Quoted 14 lines · Grant Likely
Quoted 11 lines · Gregory CLEMENT
When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.
During the system life, I monitored the CS behavior using a oscilloscope. I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used.
Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).
Quoted 4 lines
Sounds like a bug in the suspend/resume path of the spi_master, not the spi_device. Trying to work around it via the spi_device resume path is the wrong approach.

Quoted 5 lines

OK it was not clear to me that spi_resume() and spi_suspend() were specifics to devices as these functions belong to a bus structure.
So you suggest to use the suspend/resume functions of the platform_driver structure of omap2_mcspi_driver, right?

correct.

g.
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Hemanth V

2010-11-11 09:34 UTC #4 lore raw

In reply to Gregory CLEMENT

----- Original Message ----- From: "Gregory CLEMENT" <[email protected]>
To: "spi-devel-general" <[email protected]>; "linux-omap" <[email protected]>
Cc: "David Brownell" <[email protected]>; "Grant Likely" <[email protected]>; "Kevin Hilman" <[email protected]>
Sent: Wednesday, November 10, 2010 4:02 PM
Subject: [PATCH v2 2/2] spi: Force CS to be in inactive state after off-mode transition

Quoted 6 lines

When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.
During the system life, I monitored the CS behavior using a oscilloscope. I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used. Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).

Just to confirm the understanding. Are saying CHCONF[6] EPOL bit setting and CS state did not match and is actually a hardware bug. If so could u let us know which platform u are testing this on.

Thanks
Hemanth

Quoted 38 lines

Signed-off-by Gregory CLEMENT <[email protected]>

---
 drivers/spi/omap2_mcspi.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

drivers/spi/omap2_mcspi.c +9 -1

index 2a651e6..938f14c 100644
@@ -1139,6 +1139,15 @@ static u8 __initdata spi4_txdma_id[] = {
 };
 #endif
 +/* When SPI wake up, CS is in wrong state: force it to unactive state*/
+static void omap2_mcspi_resume(struct spi_device *spi)
+{
+ omap2_mcspi_enable_clocks( spi_master_get_devdata(spi->master));
+ /* We need to togle CS state for OMAP take this chang in account*/
+ omap2_mcspi_force_cs(spi, 1);
+ omap2_mcspi_force_cs(spi, 0);
+ omap2_mcspi_disable_clocks( spi_master_get_devdata(spi->master));
+}
 static int __init omap2_mcspi_probe(struct platform_device *pdev)
 {
 struct spi_master *master;

@@ -1194,6 +1203,7 @@ static int __init omap2_mcspi_probe(struct 
 platform_device *pdev)
 master->transfer = omap2_mcspi_transfer;
 master->cleanup = omap2_mcspi_cleanup;
 master->num_chipselect = num_chipselect;
+ master->resume = omap2_mcspi_resume;
  dev_set_drvdata(&pdev->dev, master);
 -- 1.7.0.4
 
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Gregory CLEMENT

author

2010-11-11 11:57 UTC #5 lore raw

Quoted 22 lines · Hemanth V

----- Original Message ----- From: "Gregory CLEMENT" <[email protected]>
To: "spi-devel-general" <[email protected]>; "linux-omap" <[email protected]>
Cc: "David Brownell" <[email protected]>; "Grant Likely" <[email protected]>; "Kevin Hilman" <[email protected]>
Sent: Wednesday, November 10, 2010 4:02 PM
Subject: [PATCH v2 2/2] spi: Force CS to be in inactive state after off-mode transition
Quoted 10 lines
When SPI wake up from OFF mode, CS is in the wrong state: force it to the inactive state.
During the system life, I monitored the CS behavior using a oscilloscope. I also activated debug in omap2_mcspi, so I saw when driver disable the clocks and restore context when device is not used. Each time the CS was in the correct state.
It was only when system was put suspend to ram with off-mode activated that on resume the CS was in wrong state( ie activated).

Quoted 4 lines

Just to confirm the understanding. Are saying CHCONF[6] EPOL bit setting and CS state did not match and is actually a hardware bug. If so could u let us know which platform u are testing this on.

Well I am not sure it is related to CHCONF[6] EPOL bit. During exchange on SPI, CS is in the good state. But when system wake up from an off-mode, CS is in its active state (high state for our configuration). I thought it was more a problem with CHCONF[20] FORCE bit, indeed this bit is at 0, so CS should be in low state. It is only when we first set this bit to 1 and then to 0, that CS go to low state. It sounds like an hardware bug on this bit, or let's say an undocumented feature ;)
CS stay in high state until the next transaction on the SPI bus, indeed as the driver use CHCONF[20] FORCE bit during exchange, it will do the transition on this bit. That's why nobody noticed it until now, because from the software point of view it works.

I didn't test it with CHCONF[6] EPOL bit set to 1.

Our silicon revision was OMAP3530-GP ES3.1.

Quoted 42 lines

Thanks
Hemanth

Quoted 38 lines

Signed-off-by Gregory CLEMENT <[email protected]>

---
drivers/spi/omap2_mcspi.c | 10 ++++++++++

1 files changed, 10 insertions(+), 0 deletions(-)

drivers/spi/omap2_mcspi.c +10 -2

index 2a651e6..938f14c 100644
@@ -1139,6 +1139,15 @@ static u8 __initdata spi4_txdma_id[] = {
 };
 #endif
+/* When SPI wake up, CS is in wrong state: force it to unactive state*/
+static void omap2_mcspi_resume(struct spi_device *spi)
+{
+ omap2_mcspi_enable_clocks( spi_master_get_devdata(spi->master));
+ /* We need to togle CS state for OMAP take this chang in account*/
+ omap2_mcspi_force_cs(spi, 1);
+ omap2_mcspi_force_cs(spi, 0);
+ omap2_mcspi_disable_clocks( spi_master_get_devdata(spi->master));
+}
 static int __init omap2_mcspi_probe(struct platform_device *pdev)
 {
 struct spi_master *master;

@@ -1194,6 +1203,7 @@ static int __init omap2_mcspi_probe(struct
 platform_device *pdev)
 master->transfer = omap2_mcspi_transfer;
 master->cleanup = omap2_mcspi_cleanup;
 master->num_chipselect = num_chipselect;
+ master->resume = omap2_mcspi_resume;
 dev_set_drvdata(&pdev->dev, master);
-- 1.7.0.4
 
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Signature · 4 lines

Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com