Re: [PATCH v11 4/5] powerpc: Add flexcan device support for p1010rdb.

On Wed, Aug 10, 2011 at 08:16:33PM +0200, Wolfgang Grandegger wrote:

On 08/10/2011 07:01 PM, Kumar Gala wrote:

quoted

On Aug 10, 2011, at 11:27 AM, Robin Holt wrote:

quoted

I added a simple clock source for the p1010rdb so the flexcan driver
could determine a clock frequency.  The p1010 flexcan device only has
an oscillator of system bus frequency divided by 2.

Signed-off-by: Robin Holt <redacted>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>,
Acked-by: Wolfgang Grandegger <redacted>,
Cc: U Bhaskar-B22300 <redacted>
Cc: socketcan-core@lists.berlios.de,
Cc: netdev@vger.kernel.org,
Cc: PPC list <redacted>
Cc: Kumar Gala <redacted>
---
arch/powerpc/platforms/85xx/Kconfig    |    2 +
arch/powerpc/platforms/85xx/Makefile   |    2 +
arch/powerpc/platforms/85xx/clock.c    |   52 ++++++++++++++++++++++++++++++++
arch/powerpc/platforms/85xx/p1010rdb.c |    8 +++++
4 files changed, 64 insertions(+), 0 deletions(-)
create mode 100644 arch/powerpc/platforms/85xx/clock.c

I dont understand how mpc85xx_clk_functions() ends up being associated with the frequency the flexcan is running at.

The function mpc85xx_clk_get_rate() returns "fsl_get_sys_freq() / 2" for
Flexcan devices.

quoted

This either seems to global or I'm missing something.

This patch extends the existing Flexcan platform driver for ARM for the
PowerPC using the device tree. Due to the nice integration of the device
tree (of-platform) into the platform driver and devices, the difference
are quite small (see patches 1..3). Apart from the endianess issue, only
the clock needs to be handled in a common way. As ARM already uses the
clk interface, we found it straight-forward to implement it for the
P1010, or more general for the 85xx, as well, instead of using an
additional helper function.

quoted

I still think the clk / freq info should be in the device tree and handled in the driver and NOT arch/powerpc platform code.

If I understand you correctly, you want the boot-loader to provide the
relevant information by fixing up the device tree, which then can be
handled arch-independently by the driver, right?

Marc and Wolfgang,

This is a very early swag at this which I worked up while driving home from dinner
this evening.  It works with my current config, but that includes at least one
bogus patch.  I will have to do more testing tomorrow.  For now, it is something
to ponder.

Thanks,
Robin
------------------------------------------------------------------------

flexcan: Prefer device tree clock frequency if available.

If our CAN device's device tree node has a clock-frequency property,
then use that value for the can devices clock frequency.  If not, fall
back to asking the platform/mach code for the clock frequency associated
with the flexcan device.

Too-early-to-be-signed-off-by: Robin Holt [off-list ref]

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 662f832..d6a87c9 100644
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c

@@ -33,6 +33,7 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/module.h>
+#include <linux/of.h>
 #include <linux/platform_device.h>
 
 #define DRV_NAME			"flexcan"

@@ -929,12 +930,25 @@ static int __devinit flexcan_probe(struct platform_device *pdev)
 	void __iomem *base;
 	resource_size_t mem_size;
 	int err, irq;
+	u32 clock_freq = 0;
 
-	clk = clk_get(&pdev->dev, NULL);
-	if (IS_ERR(clk)) {
-		dev_err(&pdev->dev, "no clock defined\n");
-		err = PTR_ERR(clk);
-		goto failed_clock;
+	if (pdev->dev.of_node) {
+		u32 *clock_freq_p;
+
+		clk = NULL;
+		clock_freq_p = (u32 *)of_get_property(pdev->dev.of_node, "clock-frequency", NULL);
+		if (clock_freq_p)
+			clock_freq = *clock_freq_p;
+	}
+
+	if (clock_freq) {
+		clk = clk_get(&pdev->dev, NULL);
+		if (IS_ERR(clk)) {
+			dev_err(&pdev->dev, "no clock defined\n");
+			err = PTR_ERR(clk);
+			goto failed_clock;
+		}
+		clock_freq = clk_get_rate(clk);
 	}
 
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);

@@ -967,7 +981,7 @@ static int __devinit flexcan_probe(struct platform_device *pdev)
 	dev->flags |= IFF_ECHO; /* we support local echo in hardware */
 
 	priv = netdev_priv(dev);
-	priv->can.clock.freq = clk_get_rate(clk);
+	priv->can.clock.freq = clock_freq;
 	priv->can.bittiming_const = &flexcan_bittiming_const;
 	priv->can.do_set_mode = flexcan_set_mode;
 	priv->can.do_get_berr_counter = flexcan_get_berr_counter;

@@ -1002,7 +1016,8 @@ static int __devinit flexcan_probe(struct platform_device *pdev)
  failed_map:
 	release_mem_region(mem->start, mem_size);
  failed_get:
-	clk_put(clk);
+	if (clk)
+		clk_put(clk);
  failed_clock:
 	return err;
 }

@@ -1020,7 +1035,8 @@ static int __devexit flexcan_remove(struct platform_device *pdev)
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	release_mem_region(mem->start, resource_size(mem));
 
-	clk_put(priv->clk);
+	if (priv->clk)
+		clk_put(priv->clk);
 
 	free_candev(dev);