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

[Dinh Nguyen <dinguyen@kernel.org>]

Hi Vinod,

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.

Dinh