On Tue, 2019-08-27 at 09:11 -0500, Dinh Nguyen wrote: > The primecell controller on some SoCs, i.e. SoCFPGA, is held in reset by > default. Until recently, the DMA controller was brought out of reset by the > bootloader(i.e. U-Boot). But a recent change in U-Boot, the peripherals > that are not used are held in reset and are left to Linux to bring them > out of reset. > > Add a mechanism for getting the reset property and de-assert the primecell > module from reset if found. This is a not a hard fail if the reset properti > is not present in the device tree node, so the driver will continue to > probe. > > Because there are different variants of the controller that may have > multiple reset signals, the code will find all reset(s) specified and > de-assert them. > > Signed-off-by: Dinh Nguyen <[email protected]> > Reviewed-by: Rob Herring <[email protected]> > --- > v6: remove the need to reset_control_get_count as > of_reset_control_array_get_optional_shared is already doing that > v5: use of_reset_control_array_get_optional_shared() > v4: cleaned up indentation in loop > fix up a few checkpatch warnings > add Reviewed-by: > v3: add a reset_control_put() > add error handling > v2: move reset control to bus code > find all reset properties and de-assert them > --- > drivers/amba/bus.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > index 100e798a5c82..f39f075abff9 100644 > --- a/drivers/amba/bus.c > +++ b/drivers/amba/bus.c > @@ -18,6 +18,7 @@ > #include <linux/limits.h> > #include <linux/clk/clk-conf.h> > #include <linux/platform_device.h> > +#include <linux/reset.h> > > #include <asm/irq.h> > > @@ -401,6 +402,19 @@ static int amba_device_try_add(struct amba_device *dev, > struct resource *parent) > ret = amba_get_enable_pclk(dev); > if (ret == 0) { > u32 pid, cid; > + struct reset_control *rstc; > + > + /* > + * Find reset control(s) of the amba bus and de-assert them. > + */ > + rstc = > of_reset_control_array_get_optional_shared(dev->dev.of_node); > + if (IS_ERR(rstc)) { > + if (PTR_ERR(rstc) != -EPROBE_DEFER) > + dev_err(&dev->dev, "Can't get amba reset!\n"); > + return PTR_ERR(rstc); > + } > + reset_control_deassert(rstc); > + reset_control_put(rstc); > > /* > * Read pid and cid based on size of resource
Reviewed-by: Philipp Zabel <[email protected]> regards Philipp
