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Date: Wed, 10 Aug 2011 22:56:20 -0500
From: Robin Holt <holt@....com>
To: Wolfgang Grandegger <wg@...ndegger.com>,
Marc Kleine-Budde <mkl@...gutronix.de>
Cc: Kumar Gala <galak@...nel.crashing.org>, Robin Holt <holt@....com>,
netdev@...r.kernel.org, U Bhaskar-B22300 <B22300@...escale.com>,
socketcan-core@...ts.berlios.de,
PPC list <linuxppc-dev@...ts.ozlabs.org>
Subject: 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:
> >
> > On Aug 10, 2011, at 11:27 AM, Robin Holt wrote:
> >
> >> 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 <holt@....com>
> >> Acked-by: Marc Kleine-Budde <mkl@...gutronix.de>,
> >> Acked-by: Wolfgang Grandegger <wg@...ndegger.com>,
> >> Cc: U Bhaskar-B22300 <B22300@...escale.com>
> >> Cc: socketcan-core@...ts.berlios.de,
> >> Cc: netdev@...r.kernel.org,
> >> Cc: PPC list <linuxppc-dev@...ts.ozlabs.org>
> >> Cc: Kumar Gala <galak@...nel.crashing.org>
> >> ---
> >> 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.
>
> > 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.
>
> > 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 <holt@....com>
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);
--
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