make the Freescale PCI driver get, prepare and enable the PCI clock
during probe(); the clock gets put upon device shutdown by the devm
approach
clock lookup is non-fatal as not all platforms may provide clock specs
in their device tree or implement a device tree based clock provider,
but failure to enable clocks after successful lookup is fatal
the driver appears to not have a remove() routine, so no reference to
the clock is kept during use, and the clock isn't released (the devm
approach will put the clock, but it won't get disabled or unprepared)
the 85xx/86xx platforms go through the probe() routine, where clock
lookup occurs and the clock gets acquired if one was specified; the
512x/83xx platforms don't pass through probe() but instead directly call
the add_bridge() routine at a point in time where the clock provider has
not been setup yet even if the platform implements one -- add comments
to the code paths as a reminder for the potential need of a workaround
in the platform's clock driver, and to keep awareness if code should get
re-arranged or moved
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Kumar Gala <ga...@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Gerhard Sittig <g...@denx.de>
---
arch/powerpc/sysdev/fsl_pci.c | 52 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)
diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
index ccfb50ddfe38..efa0916f61b6 100644
--- a/arch/powerpc/sysdev/fsl_pci.c
+++ b/arch/powerpc/sysdev/fsl_pci.c
@@ -17,6 +17,8 @@
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*/
+
+#include <linux/clk.h>
#include <linux/kernel.h>
#include <linux/pci.h>
#include <linux/delay.h>
@@ -755,6 +757,32 @@ int __init mpc83xx_add_bridge(struct device_node *dev)
const int *bus_range;
int primary;
+ /*
+ * 85xx/86xx platforms take the path through the probe() routine
+ * as one would expect, PCI related clocks get acquired there if
+ * specified
+ *
+ * 83xx/512x _don't_ pass through probe(), this add_bridge()
+ * routine instead is called from within .setup_arch() at a
+ * point in time where clock providers haven't been setup yet;
+ * so clocks cannot get acquired here -- lookup would always
+ * fail even on those platforms which implement the provider
+ *
+ * there is no counterpart for add_bridge() just like there is
+ * no remove() counterpart for probe(), so in either case the
+ * PCI related clock won't get released, and all of the
+ * 512x/83xx/85xx/86xx platforms behave in identical ways
+ *
+ * this comment is here to "keep the balance" against the
+ * probe() routine, and as a reminder to acquire clocks if the
+ * add_bridge() call should move to some later point in time
+ *
+ * until then clock providers are expected to work around the
+ * peripheral driver's not acquiring the PCI clock on those
+ * platforms where clock providers exist, while nothing needs to
+ * be done for those platforms without a clock provider
+ */
+
is_mpc83xx_pci = 1;
if (!of_device_is_available(dev)) {
@@ -1086,9 +1114,33 @@ void fsl_pci_assign_primary(void)
static int fsl_pci_probe(struct platform_device *pdev)
{
+ struct clk *clk;
int ret;
struct device_node *node;
+ /*
+ * clock lookup is non-fatal since the driver is shared among
+ * platforms and not all of them provide clocks specs in their
+ * device tree, but failure to enable a specified clock is
+ * considered fatal
+ *
+ * note that only the 85xx and 86xx platforms pass through this
+ * probe() routine, while 83xx and 512x directly invoke the
+ * mpc83xx_add_bridge() routine from within .setup_arch() code
+ */
+ clk = devm_clk_get(&pdev->dev, "ipg");
+ if (!IS_ERR(clk)) {
+ ret = clk_prepare_enable(clk);
+ if (ret) {
+ dev_err(&pdev->dev, "Could not enable PCI clock\n");
+ return ret;
+ }
+ /*
+ * TODO where to store the 'clk' reference? there appears
+ * to be no remove() routine which undoes what probe() does
+ */
+ }
+
node = pdev->dev.of_node;
ret = fsl_add_bridge(pdev, fsl_pci_primary == node);
--
1.7.10.4
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