linux-kernel - Re: [PATCH v2 1/2] usb: musb: Fix DMA for host mode

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Message-ID: <56B9C84A.6090104@cogentembedded.com>
Date:	Tue, 9 Feb 2016 14:06:50 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Joshua Henderson <joshua.henderson@...rochip.com>,
	linux-kernel@...r.kernel.org
Cc:	Cristian Birsan <cristian.birsan@...rochip.com>,
	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org
Subject: Re: [PATCH v2 1/2] usb: musb: Fix DMA for host mode

On 2/9/2016 1:15 AM, Joshua Henderson wrote:

> From: Cristian Birsan <cristian.birsan@...rochip.com>
>
> Commit ac33cdb16681 ("usb: musb: Remove ifdefs for musb_host_rx in
> musb_host.c part5") introduces a problem setting DMA host mode.
>
> This commit fixes the done condition that advances the musb schedule.
> Without this patch the the msub_advance_schedule() is called immediately
> after receiving an endpoint rx interrupt without waiting for the dma
> transfer to complete. As a consequence when the dma complete interrupt
> arrives the in_qh member of hw_ep is already null an the musb_host_rx()
> exits on !urb error case.
>
> Signed-off-by: Cristian Birsan <cristian.birsan@...rochip.com>
> Signed-off-by: Joshua Henderson <joshua.henderson@...rochip.com>
> ---
> Changes since v1:
> 	- Don't add unecessary new variable. Just correct done.
> ---
>   drivers/usb/musb/musb_host.c |   10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
> index 795a45b..6bef86f 100644
> --- a/drivers/usb/musb/musb_host.c
> +++ b/drivers/usb/musb/musb_host.c
> @@ -2006,9 +2006,15 @@ void musb_host_rx(struct musb *musb, u8 epnum)
>   			done = musb_rx_dma_in_inventra_cppi41(c, hw_ep, qh,
>   							      urb, xfer_len,
>   							      iso_err);
> -			if (done)
> +			if (done) {
> +				/* Don't call msub_advance_schedule()
> +				 * immediately after receiving an endpoint RX
> +				 * interrupt without waiting for the DMA
> +				 * transfer to complete.
> +				 */
> +				done = false;
>   				goto finish;

    By not needing the 'ret' variable I meant that you should just call 
musb_rx_dma_in_inventra_cppi41() directly from *if*.

> -			else
> +			} else
>   				dev_err(musb->controller, "error: rx_dma failed\n");

    Need to enclose all branches in {} if at least one is enclosed.

MBR, Sergei