move README.imx31 to doc/ and merge with README.mx31
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/doc/README.imx31 b/doc/README.imx31
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+U-Boot for Freescale i.MX31
+
+This file contains information for the port of U-Boot to the Freescale
+i.MX31 SoC.
+
+1. CONFIGURATION OPTIONS/SETTINGS
+---------------------------------
+
+1.1 Configuration of MC13783 SPI bus
+------------------------------------
+ The power management companion chip MC13783 is connected to the
+ i.MX31 via an SPI bus. Use the following configuration options
+ to setup the bus and chip select used for a particular board.
+
+ CONFIG_MC13783_SPI_BUS -- defines the SPI bus the MC13783 is connected to.
+ Note that 0 is CSPI1, 1 is CSPI2 and 2 is CSPI3.
+ CONFIG_MC13783_SPI_CS -- define the chip select the MC13783 s connected to.
+
+1.2 Timer precision
+-------------------
+ CONFIG_MX31_TIMER_HIGH_PRECISION
+
+ Enable higher precision timer. The low-precision timer
+ (default) provides approximately 4% error, whereas the
+ high-precision timer is about 0.4% accurate. The extra
+ accuracy is achieved at the cost of higher computational
+ overhead, which, in places where time is measured, should
+ not be critical, so, it should be safe to enable this
+ option.
