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

[Dinh Nguyen <dinguyen@kernel.org>]

Hi Geert,

On 6/4/19 11:31 AM, Geert Uytterhoeven wrote:
> 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?
> 

Yes, you're right! Will correct in V2.

Dinh