> >> >> >+ of_property_read_u32(np, "st,bch-bitflip-threshold", > >> >> >+ &pdata->bch_bitflip_threshold); > >> >> >+ > >> >> mtd->bitflip_threshold is by default set to ecc.strength (unless a > >> >> driver initializes it). > >> >> And then can be re-configured for each MTD partition separately > >> >> /sys/class/mtd/mtdX/bitflip_threshold > >> >> Refer: $kernel/Documentation/ABI/testing/sysfs-class-mtd > >> >> So, I don't think this is a HW parameter, and so should not be passed > >> >> from DT. > >> > > >> >I think the bit-flip threshold is/can be chip specific, and as we know > >> >which chip we're likely to be booting on, we can specify this via the > >> >hardware description. Thus, I think it's perfectly viable for an > >> >option to pass through DT to exist. > >> > > >> I don't think that’s the correct interpretation of bitflip_threshold. > >> > >> (1) bitflip_threshold is dependent on ecc.strength (ECC scheme) of your > >> driver. > >> MTD layers uses bitflip_threshold to warn above layers that number of > >> correctable bit-flips have reached a dangerous level beyond which driver's > >> ECC scheme may not be able to correct them. So above layers should start > >> taking additional corrective action like scrubbing. > >> @@drivers/mtd/mtdcore.c: mtd_read() > >> return ret_code >= mtd->bitflip_threshold ? -EUCLEAN : 0; > >> > >> (2) Also, user-space may control it based on how your device ages on field. > >> A fresh silicon may not show too many bitflips. But as device ages the > >> probability of simultaneous bitflips will increase. So user-space may lower > >> the bitflip_threshold to avoid accumulation of bitflips in a single page. > >> > >> Thus, bitflip_threshold should not be passed via DT. > >> It's neither a hardware parameter, nor it’s a static constant. > > > >Ah, I see. I will fixup, thanks for the explanation. > > Please wait, I'll review your [v2] series also, then you can further > send all fixes together. I'm bit caught in other commitments for 3.16, > so hopefully I'll be able to review your patches by next week.
Did you manage to find some time to review the driver at all last week? -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
