Message-ID: <6ed280af-edb6-4be7-82f4-7fc00378103e@ti.com>
Date:   Fri, 23 Nov 2018 14:35:04 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Aaro Koskinen <aaro.koskinen@....fi>
CC:     <vkoul@...nel.org>, <dan.j.williams@...el.com>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <tony@...mide.com>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] dmaengine: ti: omap-dma: Configure LCH_TYPE for OMAP1



On 22/11/2018 17.12, Russell King - ARM Linux wrote:
> On Thu, Nov 22, 2018 at 10:29:48AM +0000, Russell King - ARM Linux wrote:
>> On Tue, Nov 20, 2018 at 11:04:06PM +0200, Aaro Koskinen wrote:
>>> I had switched to PIO mode in 2015 since the WARNs about legacy DMA
>>> API were too annoying and flooding the console. And now that I tried
>>> using DMA again with g_ether, it doesn't work anymore. The device get's
>>> recognized on host side, but no traffic goes through. Switching back to
>>> PIO makes it to work again.
>>
>> A solution to that would be to do what the warning message says, and
>> update the driver to the DMAengine API.
> 
> Here's a partial conversion (not even build tested) - it only supports
> OUT transfers with dmaengine at the moment.

Thanks!

What I learned with the tusb that we need to rearrange things for
DMAengine (4cadc711cdc7 usb: musb: tusb6010_omap: Allocate DMA channels
upfront)

But that was within the musb framework, so omap_udc might be simpler.

> There's at least one thing that doesn't make sense - the driver
> apparently can transfer more than req->length bytes, surely if it does
> that, it's a serious problem - shouldn't it be noisy about that?


> Also we can't deal with the omap_set_dma_dest_burst_mode() setting -
> DMAengine always uses a 64 byte burst, but udc wants a smaller burst
> setting.  Does this matter?

The tusb also fiddled with the burst before the conversion, I believe
what the DMAengine driver is doing should be fine. If not then we fix it
while converting the omap_udc.

> 
> I've kept the old code for reference (and the driver will fall back if
> we can't get a dmaengine channel.)  I haven't been through and checked
> that we result in the channel setup largely the same either.
> 
> There will be one major difference - UDC uses element sync, where
> an element is 16bits, ep->ep.maxpacket/2 in a frame, and "packets"
> frames.  DMAengine is using frame sync, with a 16bit element, one
> element in a frame, and packets*ep->ep.maxpacket/2 frames.  This
> should be functionally equivalent but I'd like confirmation of that.

Yes, I think it should be fine also.

> 
> I'm also not sure about this:
> 
>         if (cpu_is_omap15xx())
>                 end++;
> 
> in dma_dest_len() - is that missing from the omap-dma driver?  It looks
> like a work-around for some problem on OMAP15xx, but I can't make sense
> about why it's in the UDC driver rather than the legacy DMA driver.

afaik no other legacy drivers were doing similar thing, this must be
something which is needed for the omap_udc driver to fix up something?

> 
> I'm also confused by:
> 
>         end |= start & (0xffff << 16);
> 
> also in dma_dest_len() - omap_get_dma_dst_pos() returns in the high 16
> bits the full address:
> 
>         if (dma_omap1())
>                 offset |= (p->dma_read(CDSA, lch) & 0xFFFF0000);

CDSA is OMAP_DMA_REG_2X16BIT for omap1
The CPC/CDAC holds the LSB of the _current_ DMA pointer. The code gets
the MSB of the address from the CDSA registers.

> 
> so if the address crosses a 64k physical address boundary, surely orring
> in the start address is wrong?  The more I look at dma_dest_len(), the
> more I wonder whether that and dma_src_len() are anywhere near correct,
> and whether that is a source of breakage for Aaro.

Hrm, again... the position reporting on OMAP1 is certainly not something
I would put my life on :o

> As I've already said, I've no way to test this on hardware.
> 
> Please review and let me know whether I missed anything on the OUT
> handling path.
> 
> Fixing the IN path is going to be a bit more head-scratching.
> 
>  drivers/usb/gadget/udc/omap_udc.c | 154 +++++++++++++++++++++++++++++---------
>  drivers/usb/gadget/udc/omap_udc.h |   2 +
>  2 files changed, 120 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/omap_udc.c b/drivers/usb/gadget/udc/omap_udc.c
> index 3a16431da321..a37e1d2f0f3e 100644
> --- a/drivers/usb/gadget/udc/omap_udc.c
> +++ b/drivers/usb/gadget/udc/omap_udc.c
> @@ -204,6 +204,7 @@ static int omap_ep_enable(struct usb_ep *_ep,
>  	ep->dma_channel = 0;
>  	ep->has_dma = 0;
>  	ep->lch = -1;
> +	ep->dma = NULL;
>  	use_ep(ep, UDC_EP_SEL);
>  	omap_writew(udc->clr_halt, UDC_CTRL);
>  	ep->ackwait = 0;
> @@ -576,21 +577,49 @@ static void finish_in_dma(struct omap_ep *ep, struct omap_req *req, int status)
>  static void next_out_dma(struct omap_ep *ep, struct omap_req *req)
>  {
>  	unsigned packets = req->req.length - req->req.actual;
> -	int dma_trigger = 0;
> +	struct dma_async_tx_descriptor *tx;
> +	struct dma_chan *dma = ep->dma;
> +	dma_cookie_t cookie;
>  	u16 w;
>  
> -	/* set up this DMA transfer, enable the fifo, start */
> -	packets /= ep->ep.maxpacket;
> -	packets = min(packets, (unsigned)UDC_RXN_TC + 1);
> +	packets = min_t(unsigned, packets / ep->ep.maxpacket, UDC_RXN_TC + 1);
>  	req->dma_bytes = packets * ep->ep.maxpacket;
> -	omap_set_dma_transfer_params(ep->lch, OMAP_DMA_DATA_TYPE_S16,
> -			ep->ep.maxpacket >> 1, packets,
> -			OMAP_DMA_SYNC_ELEMENT,
> -			dma_trigger, 0);
> -	omap_set_dma_dest_params(ep->lch, OMAP_DMA_PORT_EMIFF,
> -		OMAP_DMA_AMODE_POST_INC, req->req.dma + req->req.actual,
> -		0, 0);
> -	ep->dma_counter = omap_get_dma_dst_pos(ep->lch);
> +
> +	if (dma) {
> +		struct dma_slave_config cfg = {
> +			.direction = DMA_DEV_TO_MEM,
> +			.src_addr_width = DMA_SLAVE_BUSWIDTH_2_BYTE,
> +			/*
> +			 * DMAengine uses frame sync mode, setting maxburst=1
> +			 * is equivalent to element sync mode.
> +			 */
> +			.src_maxburst = 1,

We should fix the omap-dma driver for slave_sg  instead:

if (!burst)
	burst = 1;

I thought that I already did that.

> +			.src_addr = UDC_DATA_DMA,
> +		};
> +
> +		if (WARN_ON(dmaengine_slave_config(dma, &cfg)))
> +			return;
> +
> +		tx = dmaengine_prep_slave_single(dma,
> +						 req->req.dma + req->req.actual,
> +						 req->dma_bytes,
> +						 DMA_DEV_TO_MEM, 0);
> +		if (WARN_ON(!tx))
> +			return;
> +	} else {
> +		int dma_trigger = 0;
> +
> +		/* set up this DMA transfer, enable the fifo, start */
> +		/* dt = S16, cen = ep->ep.maxpacket / 2, cfn = packets */
> +		omap_set_dma_transfer_params(ep->lch, OMAP_DMA_DATA_TYPE_S16,
> +				ep->ep.maxpacket >> 1, packets,
> +				OMAP_DMA_SYNC_ELEMENT,
> +				dma_trigger, 0);
> +		omap_set_dma_dest_params(ep->lch, OMAP_DMA_PORT_EMIFF,
> +			OMAP_DMA_AMODE_POST_INC, req->req.dma + req->req.actual,
> +			0, 0);
> +		ep->dma_counter = omap_get_dma_dst_pos(ep->lch);
> +	}
>  
>  	omap_writew(UDC_RXN_STOP | (packets - 1), UDC_RXDMA(ep->dma_channel));
>  	w = omap_readw(UDC_DMA_IRQ_EN);
> @@ -599,7 +628,15 @@ static void next_out_dma(struct omap_ep *ep, struct omap_req *req)
>  	omap_writew(ep->bEndpointAddress & 0xf, UDC_EP_NUM);
>  	omap_writew(UDC_SET_FIFO_EN, UDC_CTRL);
>  
> -	omap_start_dma(ep->lch);
> +	if (dma) {
> +		cookie = dmaengine_submit(tx);
> +		if (WARN_ON(dma_submit_error(cookie)))
> +			return;
> +		ep->dma_cookie = cookie;
> +		dma_async_issue_pending(dma);
> +	} else {
> +		omap_start_dma(ep->lch);
> +	}
>  }
>  
>  static void
> @@ -607,21 +644,39 @@ finish_out_dma(struct omap_ep *ep, struct omap_req *req, int status, int one)
>  {
>  	u16	count, w;
>  
> -	if (status == 0)
> -		ep->dma_counter = (u16) (req->req.dma + req->req.actual);
> -	count = dma_dest_len(ep, req->req.dma + req->req.actual);
> +	if (ep->dma) {
> +		struct dma_tx_state state;
> +
> +		dmaengine_tx_status(ep->dma, ep->dma_cookie, &state);
> +
> +		count = req->dma_bytes - state.residual;
> +	} else {
> +		if (status == 0)
> +			ep->dma_counter = (u16) (req->req.dma + req->req.actual);
> +		count = dma_dest_len(ep, req->req.dma + req->req.actual);
> +	}
> +
>  	count += req->req.actual;
>  	if (one)
>  		count--;
> +
> +	/*
> +	 * FIXME: Surely if count > req->req.length, something has gone
> +	 * seriously wrong and we've scribbled over memory we should not...
> +	 * so surely we should be a WARN_ON() at the very least?
> +	 */
>  	if (count <= req->req.length)
>  		req->req.actual = count;
>  
> -	if (count != req->dma_bytes || status)
> -		omap_stop_dma(ep->lch);
> -
> +	if (count != req->dma_bytes || status) {
> +		if (ep->dma)
> +			dmaengine_terminate_async(ep->dma);
> +		else
> +			omap_stop_dma(ep->lch);
>  	/* if this wasn't short, request may need another transfer */
> -	else if (req->req.actual < req->req.length)
> +	} else if (req->req.actual < req->req.length) {
>  		return;
> +	}
>  
>  	/* rx completion */
>  	w = omap_readw(UDC_DMA_IRQ_EN);
> @@ -709,6 +764,7 @@ static void dma_channel_claim(struct omap_ep *ep, unsigned channel)
>  
>  	ep->dma_channel = 0;
>  	ep->lch = -1;
> +	ep->dma = NULL;
>  	if (channel == 0 || channel > 3) {
>  		if ((reg & 0x0f00) == 0)
>  			channel = 3;
> @@ -742,26 +798,44 @@ static void dma_channel_claim(struct omap_ep *ep, unsigned channel)
>  				0, 0);
>  		}
>  	} else {
> +		struct dma_chan *dma;
> +
>  		dma_channel = OMAP_DMA_USB_W2FC_RX0 - 1 + channel;
> -		status = omap_request_dma(dma_channel,
> -			ep->ep.name, dma_error, ep, &ep->lch);
> -		if (status == 0) {
> +
> +		dma = __dma_request_channel(&mask, omap_dma_filter_fn,
> +					    (void *)dma_channel);

dma_request_chan(dev, "ch_name");

where ch_name: rx0/1/2, tx0/1/2

and we don't need the omap_dma_filter_fn in here as all taken care via
the dma_slave_map


> +		if (dma) {
> +			ep->dma = dma;
>  			omap_writew(reg, UDC_RXDMA_CFG);
> -			/* TIPB */
> -			omap_set_dma_src_params(ep->lch,
> -				OMAP_DMA_PORT_TIPB,
> -				OMAP_DMA_AMODE_CONSTANT,
> -				UDC_DATA_DMA,
> -				0, 0);
> -			/* EMIFF or SDRC */
> -			omap_set_dma_dest_burst_mode(ep->lch,
> -						OMAP_DMA_DATA_BURST_4);
> -			omap_set_dma_dest_data_pack(ep->lch, 1);
> +		} else {
> +			status = omap_request_dma(dma_channel,
> +				ep->ep.name, dma_error, ep, &ep->lch);
> +			if (status == 0) {
> +				omap_writew(reg, UDC_RXDMA_CFG);
> +				/* TIPB */
> +				omap_set_dma_src_params(ep->lch,
> +					OMAP_DMA_PORT_TIPB,
> +					OMAP_DMA_AMODE_CONSTANT,
> +					UDC_DATA_DMA,
> +					0, 0);
> +				/* EMIFF or SDRC */
> +				/*
> +				 * not ok - CSDP_DST_BURST_64 selected, but this selects
> +				 * CSDP_DST_BURST_16 on omap2+ and CSDP_DST_BURST_32 on
> +				 * omap1.
> +				 */
> +				omap_set_dma_dest_burst_mode(ep->lch,
> +							OMAP_DMA_DATA_BURST_4);
> +				/* ok - CSDP_DST_PACKED set for dmaengine */
> +				omap_set_dma_dest_data_pack(ep->lch, 1);
> +			}
>  		}
>  	}
> -	if (status)
> +	if (d->dma) {
> +		ep->has_dma = 1;
> +	} else if (status) {
>  		ep->dma_channel = 0;
> -	else {
> +	} else {
>  		ep->has_dma = 1;
>  		omap_disable_dma_irq(ep->lch, OMAP_DMA_BLOCK_IRQ);
>  
> @@ -777,6 +851,10 @@ static void dma_channel_claim(struct omap_ep *ep, unsigned channel)
>  	if (status)
>  		DBG("%s no dma channel: %d%s\n", ep->ep.name, status,
>  			restart ? " (restart)" : "");
> +	else if (d->dma)
> +		DBG("%s claimed %cxdma%d dmaengine %s%s\n", ep->ep.name,
> +			is_in ? 't' : 'r', ep->dma_channel - 1,
> +			dma_chan_name(d->dma), restart ? " (restart)" : "");
>  	else
>  		DBG("%s claimed %cxdma%d lch %d%s\n", ep->ep.name,
>  			is_in ? 't' : 'r',
> @@ -850,9 +928,13 @@ static void dma_channel_release(struct omap_ep *ep)
>  		if (req)
>  			finish_out_dma(ep, req, -ECONNRESET, 0);
>  	}
> -	omap_free_dma(ep->lch);
> +	if (ep->dma)
> +		dma_release_channel(ep->dma);
> +	else
> +		omap_free_dma(ep->lch);
>  	ep->dma_channel = 0;
>  	ep->lch = -1;
> +	ep->dma = NULL;
>  	/* has_dma still set, till endpoint is fully quiesced */
>  }
>  
> diff --git a/drivers/usb/gadget/udc/omap_udc.h b/drivers/usb/gadget/udc/omap_udc.h
> index 00f9e608e755..68857ae8d763 100644
> --- a/drivers/usb/gadget/udc/omap_udc.h
> +++ b/drivers/usb/gadget/udc/omap_udc.h
> @@ -153,6 +153,8 @@ struct omap_ep {
>  	u8				dma_channel;
>  	u16				dma_counter;
>  	int				lch;
> +	struct dma_chan			*dma;
> +	dma_cookie_t			dma_cookie;
>  	struct omap_udc			*udc;
>  	struct timer_list		timer;
>  };

I try to give this a try, thanks Russell for the patch!

> 

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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