On Wed, 7 Dec 2016, Sascha Hauer wrote: > Hi Alexander, > > On Mon, Nov 28, 2016 at 10:27:33AM +0100, Alexander Kurz wrote: > > The i.MX6 series SoC type is determined by barebox by examining the > > USB_ANALOG_DIGPROG aka IMX6_ANATOP_SI_REV register. This register is located > > at a common offset for all mx6 SoC - except for i.MX6SL where a different > > offset is used. This creates a dilemma while distinguishing the mx6sl from > > non-mx6sl SOC since the SoC type identification register location is type > > specific itself. > > > > Access to undocumented and probably invalid or unpredictable registers should > > be avoided as possible. For the mx6sl detection an access to the general > > USB_ANALOG_DIGPROG @0x260 cannot be avoided when running on mx6sl. This > > register contained the value 0x00014009 for different mx6sl Rev. 1.2 based > > e-book readers using MCIMX6L7DVN10AB and MCIMX6L8DVN10AB SoC. This > > implementation assumes the value of MAJOR_UPPER (here 0x01) to be smaller > > than the smallest non-6sl MAJOR_UPPER (0x61 for mx6s). > > The i.MX6SL code would be quite straight forward and easy to merge > without this handicap. I'll probably need a few more days to swallow > this pill. I assume you already searched for better ways to detect a > i.MX6SL, right? > The uboot-implementation (get_cpu_rev() in arch/arm/cpu/armv7/mx6/soc.c) first checks the 6SL-digprog register and then proceeds with the non-6SL detection. This results in access to non-documented registers for all non-6SL SoC. My implementation limits potential trouble to 6SL and any SoC not detected yet. I did not find any good hint in the reference manuals, but anyway, if it would exist, I would assume it to be used in the freescale u-boot branch (which is similar to mainline u-boot). Regards, Alexander > > Sascha > > -- > Pengutronix e.K. | | > Industrial Linux Solutions | http://www.pengutronix.de/ | > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | > _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
