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SubjectRE: [PATCH] serial: Add OMAP high-speed UART driver.
Tony,

> -----Original Message-----
> From: linux-omap-owner@vger.kernel.org
> [mailto:linux-omap-owner@vger.kernel.org] On Behalf Of Tony Lindgren
> Sent: Tuesday, March 02, 2010 12:16 AM
> To: Raja, Govindraj
> Cc: Greg KH; linux-serial@vger.kernel.org;
> linux-omap@vger.kernel.org; linux-kernel@vger.kernel.org;
> Kevin Hilman; Olof Johansson
> Subject: Re: [PATCH] serial: Add OMAP high-speed UART driver.
>
> * Govindraj.R <govindraj.raja@ti.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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