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

[Vinod Koul <vkoul@kernel.org>]

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?

> +
> +	*(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

-- 
~Vinod