@@ -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>
@@ -756,6 +758,32 @@ 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)) {
@@ -1087,9 +1115,33 @@ 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);
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 <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Kumar Gala <galak@kernel.crashing.org> Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Gerhard Sittig <gsi@denx.de> --- arch/powerpc/sysdev/fsl_pci.c | 52 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+)