[PATCH] usb: gadget: aspeed_udc: fix handling of tx_len == 0

[Neal Liu]

> The bug is that we should still enter this loop if "tx_len" is zero.
> 
> After adding the "last" variable, then the "chunk >= 0" condition is no longer
> required but I left it for readability.
> 

Use either "chunk >=0" or "last".
I think the former is more simpler.

> Reported-by: Neal Liu <neal_liu at aspeedtech.com>
> Fixes: c09b1f372e74 ("usb: gadget: aspeed_udc: cleanup loop in
> ast_dma_descriptor_setup()")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
> ---
>  drivers/usb/gadget/udc/aspeed_udc.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/aspeed_udc.c
> b/drivers/usb/gadget/udc/aspeed_udc.c
> index d75a4e070bf7..01968e2167f9 100644
> --- a/drivers/usb/gadget/udc/aspeed_udc.c
> +++ b/drivers/usb/gadget/udc/aspeed_udc.c
> @@ -476,6 +476,7 @@ static int ast_dma_descriptor_setup(struct ast_udc_ep
> *ep, u32 dma_buf,  {
>  	struct ast_udc_dev *udc = ep->udc;
>  	struct device *dev = &udc->pdev->dev;
> +	bool last = false;
>  	int chunk, count;
>  	u32 offset;
> 
> @@ -493,14 +494,16 @@ static int ast_dma_descriptor_setup(struct
> ast_udc_ep *ep, u32 dma_buf,
>  	       "tx_len", tx_len);
> 
>  	/* Create Descriptor Lists */
> -	while (chunk > 0 && count < AST_UDC_DESCS_COUNT) {
> +	while (chunk >= 0 && !last && count < AST_UDC_DESCS_COUNT) {
> 
>  		ep->descs[ep->descs_wptr].des_0 = dma_buf + offset;
> 
> -		if (chunk > ep->chunk_max)
> +		if (chunk > ep->chunk_max) {
>  			ep->descs[ep->descs_wptr].des_1 = ep->chunk_max;
> -		else
> +		} else {
>  			ep->descs[ep->descs_wptr].des_1 = chunk;
> +			last = true;
> +		}
> 
>  		chunk -= ep->chunk_max;
> 
> --
> 2.35.1