Re: [PATCH 1/2] dmaengine: sun6i: make gate bit in sun8i's DMA engines a common quirk

[Icenowy Zheng]

ä 2017å6æ14æ GMT+08:00 äå4:32:52, Vinod Koul <vinod.koul@xxxxxxxxx> åå:
>On Mon, Jun 05, 2017 at 08:33:47PM +0800, Icenowy Zheng wrote:
>> From: Icenowy Zheng <icenowy@xxxxxxxx>
>> 
>> Originally we enable a special gate bit when the compatible indicates
>> A23/33.
>> 
>> But according to BSP sources and user manuals, more SoCs will need
>this
>> gate bit.
>> 
>> So make it a common quirk configured in the config struct.
>> 
>> Signed-off-by: Icenowy Zheng <icenowy@xxxxxxxx>
>> ---
>> Changes since original codec patchset v3:
>> - Refactored comments to cover some words found in official
>documents.
>> - Removed the comments when toggling the gate bit.
>> 
>>  drivers/dma/sun6i-dma.c | 20 +++++++++++++-------
>>  1 file changed, 13 insertions(+), 7 deletions(-)
>> 
>> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
>> index a2358780ab2c..252b59c1d1d5 100644
>> --- a/drivers/dma/sun6i-dma.c
>> +++ b/drivers/dma/sun6i-dma.c
>> @@ -101,6 +101,17 @@ struct sun6i_dma_config {
>>  	u32 nr_max_channels;
>>  	u32 nr_max_requests;
>>  	u32 nr_max_vchans;
>> +	/*
>> +	 * In the datasheets/user manuals of newer Allwinner SoCs, a
>special
>> +	 * bit (bit 2 at register 0x20) is present.
>> +	 * It's named "DMA MCLK interface circuit auto gating bit" in the
>> +	 * documents, and the footnote of this register says that this bit
>> +	 * should be set up when initializing the DMA controller.
>> +	 * Allwinner A23/A33 user manuals do not have this bit documented,
>> +	 * however these SoCs really have and need this bit, as seen in the
>> +	 * BSP kernel source code.
>> +	 */
>> +	bool gate_needed;
>
>Since this is a hw property, why is this not added as an optional DT
>property?

As it's SoC-specified.

Some SoCs need it, and some don't.

SoC info is in compatible, so there's no reason to make it a property.

>
>>  };
>>  
>>  /*
>> @@ -1009,6 +1020,7 @@ static struct sun6i_dma_config
>sun8i_a23_dma_cfg = {
>>  	.nr_max_channels = 8,
>>  	.nr_max_requests = 24,
>>  	.nr_max_vchans   = 37,
>> +	.gate_needed	 = true,
>>  };
>>  
>>  static struct sun6i_dma_config sun8i_a83t_dma_cfg = {
>> @@ -1174,13 +1186,7 @@ static int sun6i_dma_probe(struct
>platform_device *pdev)
>>  		goto err_dma_unregister;
>>  	}
>>  
>> -	/*
>> -	 * sun8i variant requires us to toggle a dma gating register,
>> -	 * as seen in Allwinner's SDK. This register is not documented
>> -	 * in the A23 user manual.
>> -	 */
>> -	if (of_device_is_compatible(pdev->dev.of_node,
>> -				    "allwinner,sun8i-a23-dma"))
>> +	if (sdc->cfg->gate_needed)
>>  		writel(SUN8I_DMA_GATE_ENABLE, sdc->base + SUN8I_DMA_GATE);
>>  
>>  	return 0;
>> -- 
>> 2.12.2
>>