Am 28.04.2015 um 00:36 schrieb Ben Shelton: > On 04/28, Richard Weinberger wrote: >> Am 27.04.2015 um 23:35 schrieb Ben Shelton: >>> I tested this against the latest version of the PL353 NAND driver that >>> Punnaiah >>> has been working to upstream (copying her on this message). With a few >>> changes >>> to that driver, I got it most of the way through initialization with on-die >>> ECC >>> enabled, but it segfaults here with a null pointer dereference because the >>> PL353 driver does not implement chip->cmd_ctrl. Instead, it implements a >>> custom override of cmd->cmdfunc that does not call cmd_ctrl. Looking >>> through >>> the other in-tree NAND drivers, it looks like most of them do implement >>> cmd_ctrl, but quite a few of them do not (e.g. au1550nd, denali, docg4). >>> >>> What do you think would be the best way to handle this? It seems like this >>> gap >>> could be bridged from either side -- either the PL353 driver could implement >>> cmd_ctrl, at least as a stub version that provides the expected behavior in >>> this case; or the on-die framework could break this out into a callback >>> function with a default implementation that the driver could override to >>> perform this behavior in the manner of its choosing. >> >> Oh, I thought every driver has to implement that function. ;-\ >> But you're right there is a corner case. >> >> What we could do is just using chip->cmdfunc() with a custom NAND command. >> i.e. chip->cmdfunc(mtd, NAND_CMD_READMODE, -1, -1); >> >> Gerhard Sittig tried to introduce such a command some time ago: >> http://lists.infradead.org/pipermail/linux-mtd/2014-April/053115.html > > That sounds reasonable to me. That's similar to how we're checking the > NAND status after reads in our current out-of-tree PL353 driver. We > added the extra command: > > + /* > + * READ0 command only, for checking read status. Note that the real command > + * here is 0x00, but we can't differentiate between READ0 where we need to > + * send a READSTART after the address bytes, or a READ0 by itself, after > + * a read status command to check the on-die ECC status. The high bit is > + * written into the unused end_cmd field, so we don't need to mask it off. > + */ > +#define NAND_CMD_READ0_ONLY 0x100 > > and then added it to the struct pl353_nand_command_format of the driver: > > static const struct pl353_nand_command_format pl353_nand_commands[] = { > {NAND_CMD_READ0, NAND_CMD_READSTART, 5, PL353_NAND_CMD_PHASE}, > + {NAND_CMD_READ0_ONLY, NAND_CMD_NONE, 0, NAND_CMD_NONE}, > {NAND_CMD_RNDOUT, NAND_CMD_RNDOUTSTART, 2, PL353_NAND_CMD_PHASE}, > {NAND_CMD_READID, NAND_CMD_NONE, 1, NAND_CMD_NONE}, > {NAND_CMD_STATUS, NAND_CMD_NONE, 0, NAND_CMD_NONE},
Yep. All you need to do in check_read_status_on_die() is switching back to reading mode. >> >> Maybe Brian can bring some light into that too... >> >>> When I build this without CONFIG_MTD_NAND_ECC_ON_DIE enabled, I get the >>> following warning here: >>> >>> In file included from drivers/mtd/nand/nand_base.c:46:0: >>> include/linux/mtd/nand_ondie.h: In function 'nand_read_subpage_on_die': >>> include/linux/mtd/nand_ondie.h:28:1: warning: no return statement in >>> function returning non-void [-Wreturn-type] >>> include/linux/mtd/nand_ondie.h: In function 'nand_read_page_on_die': >>> include/linux/mtd/nand_ondie.h:34:1: warning: no return statement in >>> function returning non-void [-Wreturn-type] >>> >>> Perhaps return an error code here, even though you'll never get past the >>> BUG()? >> >> What gcc is this? >> gcc 4.8 here does not warn, I thought it is smart enough that this function >> does never >> return. Can it be that your .config has CONFIG_BUG=n? >> Anyway, this functions clearly needs a return statement. :) > > gcc 4.7.2, and you are correct that I had CONFIG_BUG off. :) Yeah, just noticed that BUG() with CONFIG_BUG=n does not have a nonreturn attribute. So, gcc cannot know... Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/