[V2,08/13] i2c: bcm2835: Avoid clk stretch quirk for BCM2711

Commit Message

Stefan Wahren Aug. 13, 2019, 4:20 p.m. UTC

The I2C block on the BCM2711 isn't affected by the clock stretching bug.
So there is no need to apply the corresponding quirk.

Signed-off-by: Stefan Wahren <[e-mail]>
---
 drivers/i2c/busses/i2c-bcm2835.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

--
2.7.4

Comments

Wolfram Sang Aug. 14, 2019, 7:36 p.m. UTC | #1

>  static const struct of_device_id bcm2835_i2c_of_match[] = {
> -	{ .compatible = "brcm,bcm2835-i2c" },
> +	{ .compatible = "brcm,bcm2711-i2c", .data = (void *)NO_STRETCH_BUG },
> +	{ .compatible = "brcm,bcm2835-i2c", .data = (void *)STRETCH_BUG },

What about simply putting a pointer to the quirks data (or NULL) as
match_data? Then the code should be:

adap->quirks = (cast)of_device_get_match_data(&pdev->dev);

Stefan Wahren Aug. 17, 2019, 7:32 a.m. UTC | #2

Hi Wolfram,

Am 14.08.19 um 21:36 schrieb Wolfram Sang:
>>  static const struct of_device_id bcm2835_i2c_of_match[] = {
>> -	{ .compatible = "brcm,bcm2835-i2c" },
>> +	{ .compatible = "brcm,bcm2711-i2c", .data = (void *)NO_STRETCH_BUG },
>> +	{ .compatible = "brcm,bcm2835-i2c", .data = (void *)STRETCH_BUG },
> What about simply putting a pointer to the quirks data (or NULL) as
> match_data? Then the code should be:
>
> adap->quirks = (cast)of_device_get_match_data(&pdev->dev);

quirks = (const struct i2c_adapter_quirks *)of_device_get_match_data(dev);

would hit the line limit. Do you insists on the cast, because it's
actually not required?

Wolfram Sang Aug. 17, 2019, 8:30 a.m. UTC | #3

> quirks = (const struct i2c_adapter_quirks *)of_device_get_match_data(dev);
> 
> would hit the line limit. Do you insists on the cast, because it's
> actually not required?

Not at all, I mixed sth up and forgot that of_device_get_match_data
returns void*.

Patch

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index 67752f7..340da70 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -12,6 +12,7 @@ 
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>

@@ -50,6 +51,9 @@ 
 #define BCM2835_I2C_CDIV_MIN	0x0002
 #define BCM2835_I2C_CDIV_MAX	0xFFFE

+#define NO_STRETCH_BUG	false
+#define STRETCH_BUG	true
+
 struct bcm2835_i2c_dev {
 	struct device *dev;
 	void __iomem *regs;
@@ -389,7 +393,7 @@  static const struct i2c_algorithm bcm2835_i2c_algo = {
 };

 /*
- * This HW was reported to have problems with clock stretching:
+ * The BCM2835 was reported to have problems with clock stretching:
  * http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
  * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
  */
@@ -406,6 +410,9 @@  static int bcm2835_i2c_probe(struct platform_device *pdev)
 	struct clk *bus_clk;
 	struct clk *mclk;
 	u32 bus_clk_rate;
+	bool clk_stretch_bug;
+
+	clk_stretch_bug = (bool)of_device_get_match_data(&pdev->dev);

 	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
 	if (!i2c_dev)
@@ -475,7 +482,9 @@  static int bcm2835_i2c_probe(struct platform_device *pdev)
 	adap->algo = &bcm2835_i2c_algo;
 	adap->dev.parent = &pdev->dev;
 	adap->dev.of_node = pdev->dev.of_node;
-	adap->quirks = &bcm2835_i2c_quirks;
+
+	if (clk_stretch_bug)
+		adap->quirks = &bcm2835_i2c_quirks;

 	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);

@@ -501,7 +510,8 @@  static int bcm2835_i2c_remove(struct platform_device *pdev)
 }

 static const struct of_device_id bcm2835_i2c_of_match[] = {
-	{ .compatible = "brcm,bcm2835-i2c" },
+	{ .compatible = "brcm,bcm2711-i2c", .data = (void *)NO_STRETCH_BUG },
+	{ .compatible = "brcm,bcm2835-i2c", .data = (void *)STRETCH_BUG },
 	{},
 };
 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);