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Date:   Mon, 7 Jan 2019 13:11:57 -0600
From:   Bin Liu <b-liu@ti.com>
To:     Paul Elder <paul.elder@ideasonboard.com>
CC:     <laurent.pinchart@ideasonboard.com>,
        <kieran.bingham@ideasonboard.com>,
        Nicolas Boichat <drinkcat@chromium.org>,
        <gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <balbi@kernel.org>
Subject: Re: [PATCH] usb: gadget: musb: fix short isoc packets with inventra
 dma for pandaboard es
Message-ID: <20190107191137.GA25910@uda0271908>
Mail-Followup-To: Bin Liu <b-liu@ti.com>,
        Paul Elder <paul.elder@ideasonboard.com>,
        laurent.pinchart@ideasonboard.com, kieran.bingham@ideasonboard.com,
        Nicolas Boichat <drinkcat@chromium.org>, gregkh@linuxfoundation.org,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        balbi@kernel.org
References: <20181009063220.13745-1-paul.elder@ideasonboard.com>
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Hi Paul,

Sorry for the delay on reviewing it.
For the subject, can you please use

	usb: musb: gadget: fix short isoc packets with inventra dma

On Tue, Oct 09, 2018 at 02:32:20AM -0400, Paul Elder wrote:
> Handling short packets (length < max packet size) in the Inventra DMA
> engine in the MUSB driver causes the MUSB DMA controller to hang. An
> example of a problem that is caused by this problem is when streaming
> video out of a UVC gadget, only the first video frame is transferred.
> 
> For short packets (mode-0 or mode-1 DMA), MUSB_TXCSR_TXPKTRDY must be
> set manually by the driver. This was previously done in musb_g_tx
> (musb_gadget.c), but incorrectly (all csr flags were cleared, and only
> MUSB_TXCSR_MODE and MUSB_TXCSR_TXPKTRDY). Fixing that problem allows
> some requests to be transferred correctly, but multiple requests were
> often put together in one USB packet, and caused problems if the packet
> size was not a multiple of 4.
> 
> Instead, MUSB_TXCSR_TXPKTRDY is set in dma_controller_irq (musbhsdma.c),
> just like host mode transfers, then musb_g_tx forces the packet to be
> flushed, by setting MUSB_TXCSR_FLUSHFIFO.
> 
> This topic was originally tackled by Nicolas Boichat [0] [1] and is discussed

this line is longer than 75 chars.

> further at [2] as part of his GSoC project [3].
> 
> [0] https://groups.google.com/forum/?hl=en#!topic/beagleboard-gsoc/k8Azwfp75CU
> [1] https://gitorious.org/beagleboard-usbsniffer/beagleboard-usbsniffer-kernel/commit/b0be3b6cc195ba732189b04f1d43ec843c3e54c9?p=beagleboard-usbsniffer:beagleboard-usbsniffer-kernel.git;a=patch;h=b0be3b6cc195ba732189b04f1d43ec843c3e54c9
> [2] http://beagleboard-usbsniffer.blogspot.com/2010/07/musb-isochronous-transfers-fixed.html
> [3] http://elinux.org/BeagleBoard/GSoC/USBSniffer
> 
> I have forward-ported this patch from 2.6.34 to 4.19-rc1.

this line is irrelevant to the commit message, please move it down to
under '---'.

> 
> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> ---
>  drivers/usb/musb/musb_gadget.c | 21 ++++++++++++++-------
>  drivers/usb/musb/musbhsdma.c   | 21 +++++++++++----------
>  2 files changed, 25 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> index eae8b1b1b45b..d3f33f449445 100644
> --- a/drivers/usb/musb/musb_gadget.c
> +++ b/drivers/usb/musb/musb_gadget.c
> @@ -479,11 +479,16 @@ void musb_g_tx(struct musb *musb, u8 epnum)
>  			&& (request->actual == request->length))
>  				short_packet = true;
>  
> -		if ((musb_dma_inventra(musb) || musb_dma_ux500(musb)) &&
> -			(is_dma && (!dma->desired_mode ||
> -				(request->actual &
> -					(musb_ep->packet_sz - 1)))))
> -				short_packet = true;
> +		if (is_dma && (musb_dma_inventra(musb) || musb_dma_ux500(musb))) {

more than 80 chars.

> +			if (!dma->desired_mode ||

I understand you forward-port Nicolas' patch, but do you have a specific
readon to re-write this 'if' condition? I'd like to see minimum code
change in bug fixes,

> +					request->actual % musb_ep->packet_sz) {

but I like this version though, easier to read.

> +				musb_dbg(musb, "%s Flushing (FIFO) EP : KPB\n",

what is 'KPB'? the message could be more meaningful?

> +						musb_ep->end_point.name);
> +				musb_writew(epio, MUSB_TXCSR,
> +						csr | MUSB_TXCSR_FLUSHFIFO);

What if without this line? The short packet doesn't send out?  setting
TXSCR_TXPKTRDY in the dma driver is not sufficient?  TXSCR_FLUSHFIFO is
only used for aborting cases.

> +				return;
> +			}
> +		}
>  
>  		if (short_packet) {
>  			/*
> @@ -493,8 +498,10 @@ void musb_g_tx(struct musb *musb, u8 epnum)
>  			if (csr & MUSB_TXCSR_TXPKTRDY)
>  				return;
>  
> -			musb_writew(epio, MUSB_TXCSR, MUSB_TXCSR_MODE
> -					| MUSB_TXCSR_TXPKTRDY);
> +			musb_dbg(musb, "sending zero pkt (zero=%d, length=%d, actual=%d, dma->desired_mode=%d)\n",
> +				 request->zero, request->length, request->actual,

more than 80 chars.

> +				 dma->desired_mode);
> +			musb_writew(epio, MUSB_TXCSR, csr | MUSB_TXCSR_TXPKTRDY);

more than 80 chars.

>  			request->zero = 0;
>  		}
>  
> diff --git a/drivers/usb/musb/musbhsdma.c b/drivers/usb/musb/musbhsdma.c
> index a688f7f87829..e514d4700a6b 100644
> --- a/drivers/usb/musb/musbhsdma.c
> +++ b/drivers/usb/musb/musbhsdma.c
> @@ -346,12 +346,10 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
>  				channel->status = MUSB_DMA_STATUS_FREE;
>  
>  				/* completed */
> -				if ((devctl & MUSB_DEVCTL_HM)
> -					&& (musb_channel->transmit)
> -					&& ((channel->desired_mode == 0)
> -					    || (channel->actual_len &
> -					    (musb_channel->max_packet_sz - 1)))
> -				    ) {
> +				if (musb_channel->transmit &&
> +				    (!channel->desired_mode ||
> +				     (channel->actual_len %
> +				      musb_channel->max_packet_sz))) {

improper indentation.

>  					u8  epnum  = musb_channel->epnum;
>  					int offset = musb->io.ep_offset(epnum,
>  								    MUSB_TXCSR);
> @@ -363,11 +361,14 @@ static irqreturn_t dma_controller_irq(int irq, void *private_data)
>  					 */
>  					musb_ep_select(mbase, epnum);
>  					txcsr = musb_readw(mbase, offset);
> -					txcsr &= ~(MUSB_TXCSR_DMAENAB
> +					if (channel->desired_mode == 1) {
> +						txcsr &= ~(MUSB_TXCSR_DMAENAB
>  							| MUSB_TXCSR_AUTOSET);
> -					musb_writew(mbase, offset, txcsr);
> -					/* Send out the packet */
> -					txcsr &= ~MUSB_TXCSR_DMAMODE;
> +						musb_writew(mbase, offset, txcsr);

more than 80 chars.

> +						/* Send out the packet */
> +						txcsr &= ~MUSB_TXCSR_DMAMODE;
> +						txcsr |= MUSB_TXCSR_DMAENAB;
> +					}
>  					txcsr |=  MUSB_TXCSR_TXPKTRDY;
>  					musb_writew(mbase, offset, txcsr);
>  				}

Regards,
-Bin.