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

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Message-ID: <20100302060821.GI3389@atomide.com>
Date:	Mon, 1 Mar 2010 22:08:22 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	"G, Manjunath Kondaiah" <manjugk@...com>
Cc:	"Raja, Govindraj" <govindraj.raja@...com>,
	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.

* G, Manjunath Kondaiah <manjugk@...com> [100301 21:48]:
> 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?

Hmm isn't this the same as omap_get_dma_dst_pos(int lch)? If you're
trying do something that's not in dma.c, we can add a new function
for it.

> 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?

No thanks, that again leads all drivers messing with the DMA registers
directly and can easily lead to errors.

Regards,

Tony
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