Re: [RFC PATCH 2/4] dmaengine: at_hdmac: In atc_prep_dma_memset, treat value as a single byte

["Walker, Benjamin" <benjamin.walker@intel.com>]

On 2/15/2022 4:47 AM, Vinod Koul wrote:
> On 28-01-22, 11:39, Ben Walker wrote:
>> The value passed in to .prep_dma_memset is to be treated as a single
>> byte repeating pattern.
>>
>> Signed-off-by: Ben Walker <benjamin.walker@intel.com>
>> Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
>> Cc: Tudor Ambarus <tudor.ambarus@microchip.com>
>> ---
>>   drivers/dma/at_hdmac.c | 10 +++++++++-
>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
>> index 30ae36124b1db..6defca514a614 100644
>> --- a/drivers/dma/at_hdmac.c
>> +++ b/drivers/dma/at_hdmac.c
>> @@ -942,6 +942,7 @@ atc_prep_dma_memset(struct dma_chan *chan, dma_addr_t dest, int value,
>>   	struct at_desc		*desc;
>>   	void __iomem		*vaddr;
>>   	dma_addr_t		paddr;
>> +	unsigned char		fill_pattern;
>>   
>>   	dev_vdbg(chan2dev(chan), "%s: d%pad v0x%x l0x%zx f0x%lx\n", __func__,
>>   		&dest, value, len, flags);
>> @@ -963,7 +964,14 @@ atc_prep_dma_memset(struct dma_chan *chan, dma_addr_t dest, int value,
>>   			__func__);
>>   		return NULL;
>>   	}
>> -	*(u32*)vaddr = value;
>> +
>> +	/* Only the first byte of value is to be used according to dmaengine */
>> +	fill_pattern = (unsigned char)value;
> 
> why cast as unsigned?
No good reason - I didn't think negatives would be used. I've updated 
this to be signed in the v2.

> 
>> +
>> +	*(u32*)vaddr = (fill_pattern << 24) |
>> +		       (fill_pattern << 16) |
>> +		       (fill_pattern << 8) |
>> +		       fill_pattern;
>>   
>>   	desc = atc_create_memset_desc(chan, paddr, dest, len);
>>   	if (!desc) {
>> -- 
>> 2.33.1
>