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mfd: madera: Increase wait time for silicon reset

PATCH In review Richard Fitzgerald 2 participants 4 messages Oct 2, 2018

Subsystems (2)
Multifunction devices (MFD) Cirrus logic madera codec drivers
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Richard Fitzgerald

author maintainer
#0 lore raw

PATCH v2 1/2 mfd: madera: Increase wait time for silicon reset

Based on latest silicon validation, we should allow at least 2 milliseconds after DCVDD enable or hard reset before trying to communicate with the silicon.

Previously the delay was done as a side-effect of madera_disable_hard_reset(). As we also need this delay when enabling DCVDD (with or without hard reset) it is better for it to be obvious where it happens in every power-up sequence rather than hidden within another call in some cases. So it has been moved out into a separate function call.

Signed-off-by Richard Fitzgerald <[email protected]>
---
 drivers/mfd/madera-core.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)
drivers/mfd/madera-core.c +12 -1
index 440030cecbbd..1dedfe68a3dc 100644
@@ -135,6 +135,15 @@ EXPORT_SYMBOL_GPL(madera_name_from_type);
 #define MADERA_BOOT_POLL_INTERVAL_USEC		5000
 #define MADERA_BOOT_POLL_TIMEOUT_USEC		25000
 
+static void madera_por_delay(void)
+{
+	/*
+	 * Delay after DCVDD enable or hard reset to allow for silicon POR
+	 * (power-on reset).
+	 */
+	usleep_range(2000, 3000);
+}
+
 static int madera_wait_for_boot(struct madera *madera)
 {
 	ktime_t timeout;

@@ -209,7 +218,6 @@ static void madera_disable_hard_reset(struct madera *madera)
 		return;
 
 	gpiod_set_raw_value_cansleep(madera->pdata.reset, 1);
-	usleep_range(1000, 2000);
 }
 
 static int __maybe_unused madera_runtime_resume(struct device *dev)

@@ -225,6 +233,8 @@ static int __maybe_unused madera_runtime_resume(struct device *dev)
 		return ret;
 	}
 
+	madera_por_delay();
+
 	regcache_cache_only(madera->regmap, false);
 	regcache_cache_only(madera->regmap_32bit, false);
 

@@ -440,6 +450,7 @@ int madera_dev_init(struct madera *madera)
 	}
 
 	madera_disable_hard_reset(madera);
+	madera_por_delay();
 
 	regcache_cache_only(madera->regmap, false);
 	regcache_cache_only(madera->regmap_32bit, false);
Signature · 1 line
2.11.0
author maintainer
#1 lore raw

PATCH v2 2/2 mfd: madera: Wait for BOOT_DONE before reading device ID

It isn't safe to read the device ID in the SOFTWARE_RESET register until the silicon boot sequence has completed. This patch rearranges the code to wait until BOOT_DONE is set.

If we don't have a hard reset line we want to defer writing a soft reset command until we have identified the silicon as something we recognize. As the BOOT_DONE bit is sticky it is safe to wait for it without issuing a soft reset first, because the most recent power-up will have caused a boot sequence and set the bit. Note that the boot sequence is not the same as a reset so we still have to soft reset to get the codec into a known state.

Signed-off-by Stuart Henderson <[email protected]>
Signed-off-by Richard Fitzgerald <[email protected]>
---
 drivers/mfd/madera-core.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)
drivers/mfd/madera-core.c +13 -9
index 1dedfe68a3dc..e114ca5e6c3f 100644
@@ -455,10 +455,13 @@ int madera_dev_init(struct madera *madera)
 	regcache_cache_only(madera->regmap, false);
 	regcache_cache_only(madera->regmap_32bit, false);
 
-	/*
-	 * Now we can power up and verify that this is a chip we know about
-	 * before we start doing any writes to its registers.
-	 */
+	/* BOOT_DONE must be set before we can read the device ID */
+	ret = madera_wait_for_boot(madera);
+	if (ret) {
+		dev_err(madera->dev, "Device failed initial boot: %d\n", ret);
+		goto err_reset;
+	}
+
 	ret = regmap_read(madera->regmap, MADERA_SOFTWARE_RESET, &hwid);
 	if (ret) {
 		dev_err(dev, "Failed to read ID register: %d\n", ret);

@@ -528,12 +531,13 @@ int madera_dev_init(struct madera *madera)
 		ret = madera_soft_reset(madera);
 		if (ret)
 			goto err_reset;
-	}
 
-	ret = madera_wait_for_boot(madera);
-	if (ret) {
-		dev_err(madera->dev, "Device failed initial boot: %d\n", ret);
-		goto err_reset;
+		ret = madera_wait_for_boot(madera);
+		if (ret) {
+			dev_err(madera->dev, "Device failed initial soft reboot: %d\n",
+				ret);
+			goto err_reset;
+		}
 	}
 
 	ret = regmap_read(madera->regmap, MADERA_HARDWARE_REVISION,
Signature · 1 line
2.11.0
maintainer Reviewed-by on v2 2/2
#2 lore raw

Re: [PATCH v2 2/2] mfd: madera: Wait for BOOT_DONE before reading device ID

Quoted 13 lines · Richard Fitzgerald

It isn't safe to read the device ID in the SOFTWARE_RESET register until the silicon boot sequence has completed. This patch rearranges the code to wait until BOOT_DONE is set.

If we don't have a hard reset line we want to defer writing a soft reset command until we have identified the silicon as something we recognize. As the BOOT_DONE bit is sticky it is safe to wait for it without issuing a soft reset first, because the most recent power-up will have caused a boot sequence and set the bit. Note that the boot sequence is not the same as a reset so we still have to soft reset to get the codec into a known state.

Quoted 3 lines
Signed-off-by Stuart Henderson <[email protected]>
Signed-off-by Richard Fitzgerald <[email protected]>

---

Reviewed-by Charles Keepax <[email protected]>

Thanks,
Charles

maintainer Reviewed-by on v2 1/2
#3 lore raw
In reply to Richard Fitzgerald
Quoted 11 lines · Richard Fitzgerald

Based on latest silicon validation, we should allow at least 2 milliseconds after DCVDD enable or hard reset before trying to communicate with the silicon.

Previously the delay was done as a side-effect of madera_disable_hard_reset(). As we also need this delay when enabling DCVDD (with or without hard reset) it is better for it to be obvious where it happens in every power-up sequence rather than hidden within another call in some cases. So it has been moved out into a separate function call.

Quoted 2 lines
Signed-off-by Richard Fitzgerald <[email protected]>

---

Reviewed-by Charles Keepax <[email protected]>

Thanks,
Charles