On Mon, 2019-08-26 at 10:42 -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 <dinguyen@xxxxxxxxxx>
> Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> ---
> 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 | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
> index 100e798a5c82..f8a7cb74c3cf 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 +402,24 @@ 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;
> + int count;
> + struct reset_control *rstc;
> +
> + /*
> + * Find reset control(s) of the amba bus and de-assert them.
> + */
> + count = reset_control_get_count(&dev->dev);
> + while (count > 0) {
> + rstc = of_reset_control_array_get_optional_shared(dev->dev.of_node);
You can drop the loop, the rstc returned by of_reset_control_array_get()
already controls all resets together.
regards
Philipp
