Hi Anup, On Wed, Oct 07, 2015 at 03:33:50AM +0000, Anup Patel wrote: > > -----Original Message----- > > From: Florian Fainelli [mailto:f.fainelli@xxxxxxxxx] > > > > On 06/10/15 15:25, Scott Branden wrote: > > > > Then instead of adding a "reset flag" to Device Tree, another approach could be > > to put the desired or currently configured exhaustive list of NAND timings in > > Device Tree, and based on that you could have this: > > > > - the NAND controller driver finds that these timings match the current > > configuration, you are good to go > > > > - the NAND controller drivers finds a difference in how current timings are > > configured vs. desired timings, and issues a controller reset, prior to applying > > new timing configuration > > To add to this ... > > The mechanism to reset is BRCM NAND controller is SOC specific so the > SoC independent BRCM NAND driver (i.e. brcmnand.c) does not know how > to reset the NAND controller. > > For iProc SoC family, the NAND controller reset is through IDM register > space which is only iomap'ed by iproc_nand.c. > > We might end-up having one more SoC specific callback which will be > Provided by iproc_nand.c to brcmnand.c. > > > > > - no timings are configured, reset the controller and use existing auto-detection > > capabilities like ONFI modes > > > > Typically you would put the desired timings instead of the currently configured > > timings though.. > > Overall, it would good to support timing parameters through DT or ONFI but > for now have we can rely on reset and auto-devid configuration. I don't want to support a DT property that is only used as a workaround for the right solution. That means the property may quickly become obsolete, yet we have to support it forever. > > >> compatible = "brcm,iproc-nand-ns2", ...; > > >> > > > As described above - the option is not SoC specific. It is system > > > specific. In some systems we may wish to reset the NAND controller in > > > linux. In some we may wish to rely on initialization that has already > > > been done to speed up boot times. > > > > It seems to me like having this property is fine as long as you are describing that > > the controller *needs* a reset to operate properly, it does not strike me as a > > particularly well suited property if its side effect and main usage is to keep or > > wipe-out existing NAND timings. > > IMHO, having SoC specific compatible string for NS2 is like saying > NAND controller on NS2 is different from other iProc SoCs whereas > Having optional DT flags for quirks/work-arounds (e.g. NAND controller > reset) is like saying NAND controller on NS2 same as other iProc SoCs > but some additional programming is required. OK... so what is the reason that you have to reset the controller on NS2 and not Cygnus? Is it a SoC difference (i.e., compatible string)? Firmware/bootloader difference? So far, all statements have been non-specific, AFAICT. Brian -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
