> -----Original Message----- > From: svenkatr@xxxxxxxxx [mailto:svenkatr@xxxxxxxxx] On > Behalf Of Venkatraman S > Sent: Tuesday, March 02, 2010 7:16 PM > To: Tony Lindgren; G, Manjunath Kondaiah; Raja, Govindraj; > Greg KH; linux-serial@xxxxxxxxxxxxxxx; > linux-omap@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > Kevin Hilman; Olof Johansson > Subject: Re: [PATCH] serial: Add OMAP high-speed UART driver. > > On Tue, Mar 2, 2010 at 12:22 PM, Tony Lindgren > <tony@xxxxxxxxxxx> wrote: > > * G, Manjunath Kondaiah <manjugk@xxxxxx> [100301 22:24]: > >> > >> > >> > >> > > > > + 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. > >> > >> The omap_get_dma_dst_pos(int lch) is for read operation in > CDAC register. > >> But, We need to write required value into CDAC register. > For this, I propose: > >> > >> omap_set_dma_dst_pos(int lch, int value) which does not > exist in current dma > >> driver. > > > > OK, it that's needed. > > > > Tony > > -- > CDAC is a shadow register used for monitoring the DMA channel. > I think it would be a lot > simpler if omap_start_dma() always resets CDAC to 0, and the > UART driver > just not set it explicitly. This seems to be better option than exposing CDAC read/write API to other drivers since user need to write '0' before starting any DMA transfer which can be be done in omap_start_dma(). I am wondering how other drivers are using DMA transfer API's without resetting CDAC to zero. -Manjunath -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
