linux-kernel - RE: [PATCH] serial: Add OMAP high-speed UART driver.

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Date:	Tue, 2 Mar 2010 11:21:13 +0530
From:	"G, Manjunath Kondaiah" <manjugk@...com>
To:	Tony Lindgren <tony@...mide.com>,
	"Raja, Govindraj" <govindraj.raja@...com>
CC:	Greg KH <greg@...ah.com>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Olof Johansson <olof@...om.net>
Subject: RE: [PATCH] serial: Add OMAP high-speed UART driver.

Tony,

> -----Original Message-----
> From: linux-omap-owner@...r.kernel.org 
> [mailto:linux-omap-owner@...r.kernel.org] On Behalf Of Tony Lindgren
> Sent: Tuesday, March 02, 2010 12:16 AM
> To: Raja, Govindraj
> Cc: Greg KH; linux-serial@...r.kernel.org; 
> linux-omap@...r.kernel.org; linux-kernel@...r.kernel.org; 
> Kevin Hilman; Olof Johansson
> Subject: Re: [PATCH] serial: Add OMAP high-speed UART driver.
> 
> * Govindraj.R <govindraj.raja@...com> [100301 06:40]:
> > --- /dev/null
> > +++ b/drivers/serial/omap-serial.c
> > +
> > +static void serial_omap_stop_tx(struct uart_port *port)
> > +{
> > +	struct uart_omap_port *up = (struct uart_omap_port *)port;
> > +
> > +	if (up->use_dma &&
> > +		up->uart_dma.tx_dma_channel != OMAP_UART_DMA_CH_FREE) {
> > +		/*
> > +		 * Check if dma is still active . If yes do nothing,
> 
> Looks like an extra space here before the period above.
> 
> ...
> 
> > +static int serial_omap_start_rxdma(struct uart_omap_port *up)
> > +{
> > +	int ret = 0;
> > +
> > +	if (up->uart_dma.rx_dma_channel == -1) {
> > +		ret = omap_request_dma(up->uart_dma.uart_dma_rx,
> > +				"UART Rx DMA",
> > +				(void *)uart_rx_dma_callback, up,
> > +				&(up->uart_dma.rx_dma_channel));
> > +		if (ret < 0)
> > +			return ret;
> > +
> > +		omap_set_dma_src_params(up->uart_dma.rx_dma_channel, 0,
> > +				OMAP_DMA_AMODE_CONSTANT,
> > +				up->uart_dma.uart_base, 0, 0);
> > +		omap_set_dma_dest_params(up->uart_dma.rx_dma_channel, 0,
> > +				OMAP_DMA_AMODE_POST_INC,
> > +				up->uart_dma.rx_buf_dma_phys, 0, 0);
> > +		
> omap_set_dma_transfer_params(up->uart_dma.rx_dma_channel,
> > +				OMAP_DMA_DATA_TYPE_S8,
> > +				up->uart_dma.rx_buf_size, 1,
> > +				OMAP_DMA_SYNC_ELEMENT,
> > +				up->uart_dma.uart_dma_rx, 0);
> > +	}
> > +	up->uart_dma.prev_rx_dma_pos = up->uart_dma.rx_buf_dma_phys;
> > +	if (cpu_is_omap44xx())
> > +		omap_writel(0, OMAP44XX_DMA4_BASE
> > +			+ OMAP_DMA4_CDAC(up->uart_dma.rx_dma_channel));
> > +	else
> > +		omap_writel(0, OMAP34XX_DMA4_BASE
> > +			+ OMAP_DMA4_CDAC(up->uart_dma.rx_dma_channel));
> 
> NAK. Please don't use omap_read/write for for new code. And do not
> tinker with the omap hardware registers directly in the driver.
> 
> This needs to be done properly in arch/arm/plat-omap/dma.c instead.

Thanks for the suggestion.

Currently, dma_read/dma_write are #define's in dma.c which cannot be 
accessed outside dma.c. I don't see any API's in dma.c for setting required 
value for this register?

Can we move dma_read/dma_write to header file so that it can be global or 
Is there alternate way to perform this operation with existing dma driver?

-Manjunath--
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