Hi, On Fri, Nov 20, 2015 at 06:42:08PM +0000, Simon Arlott wrote: > On 17/11/15 17:55, Brian Norris wrote: > > On Tue, Nov 17, 2015 at 07:41:21AM +0000, Simon Arlott wrote: > >> On 17/11/15 00:40, Brian Norris wrote: > >> > + bcm-kernel-feedback-list > >> > > >> > On Mon, Nov 16, 2015 at 10:05:39PM +0000, Simon Arlott wrote: > >> >> If an error occurs in flash above 4GB in PIO mode then the EXT_ADDR > >> >> registers will be set to the location of the error and never cleared. > >> >> > >> >> Reset them to 0 before reading. > >> >> > >> >> Signed-off-by: Simon Arlott <[email protected]> > >> > > >> > Patch looks OK. Did you see this problem in practice, or is this just > >> > theoretical? I thought the documentation seemed to suggest these > >> > registers were cleared together with their non-_EXT counterparts. But > >> > implementation definitely trumps documentation for HW. > >> > >> It's theoretical (I don't have 4GB+ flash), but the Broadcom version of > >> the NAND driver does this. > > > > That's a funny thing to say :) There never really was a single "Broadcom > > version" until we settled on upstreaming this one. It's a direct > > descendant of this [1], which also does not do these writes, and was > > tested on >4GB flash, though not extensively. > > > > Which product line did you get your driver from, then? > > I have a file called > bcm963xx_4.12L.06B_consumer/kernel/linux/drivers/mtd/brcmnand/brcmnand_base.c: > > /* Clear ECC registers */ > chip->ctrl_write(BCHP_NAND_ECC_CORR_ADDR, 0); > chip->ctrl_write(BCHP_NAND_ECC_UNC_ADDR, 0); > #if CONFIG_MTD_BRCMNAND_VERSION >= CONFIG_MTD_BRCMNAND_VERS_1_0 > chip->ctrl_write(BCHP_NAND_ECC_CORR_EXT_ADDR, 0); > chip->ctrl_write(BCHP_NAND_ECC_UNC_EXT_ADDR, 0); > #endif
I'd bet it was done without ever actually testing or observing the behavior. The version 1.0 controller is extremely old and most definitely never was used with >4GB NAND. But since this should be harmless and has some small chance of fixing a bug, I'll take it anyway. > There's also a workaround (brcmnand_handle_false_read_ecc_unc_errors) > that I'm going to write a patch for as it affects my v4.0 device. It'd > be useful to know which version of the controller fixes the issue: > > /* Flash chip returns errors > || There is a bug in the controller, where if one reads from an > erased block that has NOT been written to, > || this error is raised. > || (Writing to OOB area does not have any effect on this bug) > || The workaround is to also look into the OOB area, to see if they > are all 0xFF > */ That one's pretty ugly... but that's a different story. Brian -- 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/
