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 4dfd61df8aba..bee8011d6bd7 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> @@ -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); -- 1.7.10.4 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev