On 12/17/2012 02:58 PM, Mitch Bradley wrote: > On 12/17/2012 11:36 AM, Stephen Warren wrote: >> On 12/17/2012 05:10 AM, Laxman Dewangan wrote: >>> Nvidia's Tegra has multiple uart controller which supports: >>> - APB dma based controller fifo read/write. >>> - End Of Data interrupt in incoming data to know whether end >>> of frame achieve or not. >>> - Hw controlled RTS and CTS flow control to reduce SW overhead. >> >>> diff --git a/Documentation/devicetree/bindings/serial/nvidia,serial-tegra.txt b/Documentation/devicetree/bindings/serial/nvidia,serial-tegra.txt >> >>> +NVIDIA Tegra20/Tegra30 high speed (dma based) UART controller driver. >>> + >>> +Required properties: >>> +- compatible : should be "nvidia,tegra20-hsuart", "nvidia,tegra30-hsuart". >> >> One question that isn't addressed here is: >> >> Tegra has 5 UARTs. All of them can use the existing 8250.c by specifying >> compatible = "nvidia,tegra20-uart". > > The way it is supposed to work is that the compatible property should > list "nvidia,tegra30-hsuart" first, followed by a fallback name that > refers to the generic 8250 compatibility. Having the 8250.c driver bind > to the more-specific tegra30-hsuart name is wrong. 8250.c binds to nvidia,tegra20-uart, so that aspect is fine. However, the real issue is that we probably want 4 of the 5 ports to use the plain old 8250.c (so as not to use up too many DMA channels), but just 1 of the ports to use the DMA-capable high-performance driver (e.g. the one that a particular board has hooked up to a Bluetooth radio). The only way to do that with DT that I know of would be to specify different subsets of legal compatible values for each UART in the per-board .dts file. -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
