> Subject: Re: [RFC 1/2] dt-bindings: imx-ocotp: Add fusable-node property > > On 20.05.2019 06:06, Peng Fan wrote: > > Introduce fusable-node property for i.MX OCOTP driver. > > The property will only be used by Firmware(eg. U-Boot) to runtime > > disable the nodes. > > > > Take i.MX6ULL for example, there are several parts that only have > > limited modules enabled controlled by OCOTP fuse. It is not flexible > > to provide several dts for the serval parts, instead we could provide > > one device tree and let Firmware to runtime disable the device tree > > nodes for those modules that are disable(fused). > > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx> > > --- > > > > Currently NXP vendor use U-Boot to set status to disabled for devices > > that could not function, > > > https://source.codeaurora.org/external/imx/uboot-imx/tree/arch/arm/mac > > h-imx/mx6/module_fuse.c?h=imx_v2018.03_4.14.98_2.0.0_ga#n149 > > But this approach is will not work if kernel dts node path changed. > > > > There are two approaches to resolve: > > > > 1. This patch is to add a fusable-node property, and Firmware will parse > > the property and read fuse to decide whether to disable or keeep > enable > > the nodes. > > > > 2. There is another approach is that add nvmem-cells for all nodes that > > could be disabled(fused). Then in each linux driver to use nvmem > > api to detect fused or not, or in linux driver common code to check > > device functionable or not with nvmem API. > > > > > > To make it easy to work, we choose [1] here. Please advise whether it > > is acceptable, because the property is not used by linux driver in > > approach [1]. Or you prefer [2] or please advise if any better solution. > > Couldn't firmware parse nvmem-cells? Even without a full nvmem subsystem > it would be possible for imx-specific code to walk the entire device tree, parse > nvmem-cells and disable nodes which are disabled by fuse. Firmware could parse nvmem-cells, but there are lots of modules that could be fused. If using nvmem-cells, that means need to add nvmem property for all the modules that could be fused. To make is looks cleaner, so introduced a fusable-node property. Regards, Peng. > > -- > Regards, > Leonard
