Subject: [PATCH] s3c2410_udc: Add handling for S3C244X dual-packet mode

From: [email-masked] (Vasily Khoruzhick)
Date: Mon, 6 Dec 2010 21:39:46 +0200

On Monday 30 August 2010 17:34:22 Vasily Khoruzhick wrote:
> From: Fabian Godehardt <[email-masked]>
> 
> This is a patch that seems to make the USB hangs on the S3C244X go away.
> At least a good amount of ping torture didn't make them come back so far.
> 
> The issue is that, if there are several back-to-back packets, sometimes no
> interrupt is generated for one of them. This seems to be caused by the
> mysterious dual packet mode, which the USB hardware enters automatically
> if the endpoint size is half that of the FIFO. (On the 244X, this is the
> normal situation for bulk data endpoints.)
> 
> There is also a timing factor in this. It seems that what happens is that
> the USB hardware automatically sends an acknowledgement if there is only
> one packet in the FIFO (the FIFO has space for two). If another packet
> arrives before the host has retrieved and acknowledged the previous one,
> no interrupt is generated for that second one.
> 
> However, there may be an indication. There is one undocumented bit (none
> of the 244x manuals document it), OUT_CRS1_REG[1], that seems to be set
> suspiciously often when this condition occurs. There is also
> CLR_DATA_TOGGLE, OUT_CRS1_REG[7], which may have a function related to
> this. (The Samsung manual is rather terse on that, as usual.)
> 
> This needs to be examined further. For now, the patch seems to do the
> trick.
> 
> Signed-off-by: Vasily Khoruzhick <[email-masked]>
> ---
>  drivers/usb/gadget/s3c2410_udc.c |   16 +++++++++++++++-
>  1 files changed, 15 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/usb/gadget/s3c2410_udc.c
> b/drivers/usb/gadget/s3c2410_udc.c index ea2b3c7..fed323c 100644
> --- a/drivers/usb/gadget/s3c2410_udc.c
> +++ b/drivers/usb/gadget/s3c2410_udc.c
> @@ -902,7 +902,7 @@ static irqreturn_t s3c2410_udc_irq(int dummy, void
> *_dev) int pwr_reg;
>  	int ep0csr;
>  	int i;
> -	u32 idx;
> +	u32 idx, idx2;
>  	unsigned long flags;
> 
>  	spin_lock_irqsave(&dev->lock, flags);
> @@ -1017,6 +1017,20 @@ static irqreturn_t s3c2410_udc_irq(int dummy, void
> *_dev) }
>  	}
> 
> +	/* what else causes this interrupt? a receive! who is it? */
> +	if (!usb_status && !usbd_status && !pwr_reg && !ep0csr) {
> +		for (i = 1; i < S3C2410_ENDPOINTS; i++) {
> +			idx2 = udc_read(S3C2410_UDC_INDEX_REG);
> +			udc_write(i, S3C2410_UDC_INDEX_REG);
> +
> +			if (udc_read(S3C2410_UDC_OUT_CSR1_REG) & 0x1)
> +				s3c2410_udc_handle_ep(&dev->ep[i]);
> +
> +			/* restore index */
> +			udc_write(idx2, S3C2410_UDC_INDEX_REG);
> +		}
> +	}
> +
>  	dprintk(DEBUG_VERBOSE, "irq: %d s3c2410_udc_done.\n", IRQ_USBD);
> 
>  	/* Restore old index */

Ping? s3c2410_udc is broken for s3c244x for ages, fix is available, why not to 
apply it?

Regards
Vasily