Re: [PATCH 2/2] dmagengine: pl330: add code to get reset property

[Geert Uytterhoeven <geert@linux-m68k.org>]

Hi Dinh,

On Tue, Jun 4, 2019 at 4:21 PM Dinh Nguyen <dinguyen@kernel.org> wrote:
> On 6/4/19 7:14 AM, Vinod Koul wrote:
> > On 23-05-19, 19:28, Dinh Nguyen wrote:
> >> The DMA controller on some SoCs can be held in reset, and thus requires
> >> the reset signal(s) to deasserted. Most SoCs will have just one reset
> >> signal, but there are others, i.e. Arria10/Stratix10 will have an
> >> additional reset signal, referred to as the OCP.
> >>
> >> Add code to get the reset property from the device tree for deassert and
> >> assert.
> >>
> >> Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
> >> ---
> >>  drivers/dma/pl330.c | 38 ++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 38 insertions(+)
> >>
> >> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> >> index 6e6837214210..6018c43e785d 100644
> >> --- a/drivers/dma/pl330.c
> >> +++ b/drivers/dma/pl330.c
> >> @@ -29,6 +29,7 @@
> >>  #include <linux/err.h>
> >>  #include <linux/pm_runtime.h>
> >>  #include <linux/bug.h>
> >> +#include <linux/reset.h>
> >>
> >>  #include "dmaengine.h"
> >>  #define PL330_MAX_CHAN              8
> >> @@ -500,6 +501,9 @@ struct pl330_dmac {
> >>      unsigned int num_peripherals;
> >>      struct dma_pl330_chan *peripherals; /* keep at end */
> >>      int quirks;
> >> +
> >> +    struct reset_control    *rstc;
> >> +    struct reset_control    *rstc_ocp;
> >>  };
> >>
> >>  static struct pl330_of_quirks {
> >> @@ -3028,6 +3032,30 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
> >>
> >>      amba_set_drvdata(adev, pl330);
> >>
> >> +    pl330->rstc = devm_reset_control_get_optional(&adev->dev, "dma");
> >> +    if (IS_ERR(pl330->rstc)) {
> >> +            dev_err(&adev->dev, "No reset controller specified.\n");
> >
> > Wasnt this optional??
>
> Yes, this is optional. The call devm_reset_control_get_optional() will
> just return NULL if the reset property is not there, but an error
> pointer if something really went wrong. Thus, I'm using IS_ERR() for the
> error checking.

So the error message is incorrect, as this is a real error condition?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds