mtd: nand: Disable subpage writes for drivers without ecc->hwctl

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=44991b3d19cd71eabe68019ae7cb91df0c929614
Commit:     44991b3d19cd71eabe68019ae7cb91df0c929614
Parent:     6166a76f5ef7619faa28b38d7817e5fe0e509942
Author:     Helmut Schaa <helmut.schaa at googlemail.com>
AuthorDate: Wed Apr 9 11:13:24 2014 +0200
Committer:  Brian Norris <computersforpeace at gmail.com>
CommitDate: Fri Dec 18 18:15:28 2015 -0800

    mtd: nand: Disable subpage writes for drivers without ecc->hwctl
    
    nand_write_subpage_hwecc causes a crash if the driver did not register
    ecc->hwctl or ecc->calculate. Fix this by disabling subpage writes if
    ecc->hwctl or ecc->calculate is not provided by the driver.
    
    This behavior was introduced in commit 837a6ba4f3b6d23026674e6af6b6849a4634fff9
    "mtd: nand: subpage write support for hardware based ECC schemes".
    
    This fixes a crash with fsl_elbc_nand and maybe others:
    
    Unable to handle kernel paging request for instruction fetch
    Faulting instruction address: 0x00000000
    Oops: Kernel access of bad area, sig: 11 [#1]
    SMP NR_CPUS=2 P1020 RDB
    Modules linked in: ath9k ath9k_common pppoe ppp_async option iptable_nat ath9k_hw ath usb_wwan pppox ppp_generic nf_nat_ipv4 nf_conntrack_ipv4 mac80211 ipt_MASQUERADE cfg80211 xt_time xt_tcpudp xt_state xt_quota xt_policy xt_pkttype xt_owner xt_nat xt_multiport xt_mh
    CPU: 1 PID: 2161 Comm: ubiformat Not tainted 3.10.26 #6
    task: efbc2700 ti: c7950000 task.ti: c7950000
    NIP: 00000000 LR: c01a495c CTR: 00000000
    REGS: c7951cb0 TRAP: 0400   Not tainted  (3.10.26)
    MSR: 00029000 <CE,EE,ME>  CR: 24002028  XER: 00000000
    
    GPR00: c01a4b6c c7951d60 efbc2700 ef84b000 00000001 00000000 000001ff c7800500
    GPR08: 00000000 00000000 efae5e40 c01a4ae4 24002022 10023418 c7951e5c c7800500
    GPR16: c017b6a8 00000000 0000003f c053404c 00000000 00000004 00000000 00000003
    GPR24: 00000010 00000200 ef84b000 c7800d00 c7800000 c7800500 ef84b1c8 00000000
    NIP [00000000]   (null)
    LR [c01a495c] nand_write_subpage_hwecc+0x74/0x174
    Call Trace:
    [c7951d60] [c7951d64] 0xc7951d64 (unreliable)
    [c7951da0] [c01a4b6c] nand_write_page+0x88/0x198
    [c7951dd0] [c01a5f7c] nand_do_write_ops+0x2f4/0x39c
    [c7951e40] [c01a61e0] nand_write+0x58/0x84
    [c7951e80] [c019e29c] mtdchar_write+0x1dc/0x28c
    [c7951ef0] [c00aba84] vfs_write+0xcc/0x1ac
    [c7951f10] [c00ac04c] SyS_write+0x4c/0x90
    [c7951f40] [c000cd84] ret_from_syscall+0x0/0x3c
     --- Exception: c01 at 0x48050ed8
         LR = 0x100071b8
     Instruction dump:
     XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
     XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
     ---[ end trace 161d3c65a2a15cb8 ]---
    
    Kernel panic - not syncing: Fatal exception
    
    [Brian: editorial note - we've applied a previous fix for the driver in
    question (fsl_elbc_nand) long ago:
    commit f034d87def51 ("mtd: eLBC NAND: fix subpage write support")
    but this still makes sense, and it could solve issues on some other
    unforseen driver.]
    
    Cc: Pekon Gupta <pekon.gupta at gmail.com>
    Cc: Artem Bityutskiy <artem.bityutskiy at linux.intel.com>
    Cc: David Woodhouse <David.Woodhouse at intel.com>
    Signed-off-by: Helmut Schaa <helmut.schaa at googlemail.com>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 drivers/mtd/nand/nand_base.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 8bb8ebd6..928081b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -4167,7 +4167,7 @@ int nand_scan_tail(struct mtd_info *mtd)
 			ecc->write_oob = nand_write_oob_std;
 		if (!ecc->read_subpage)
 			ecc->read_subpage = nand_read_subpage;
-		if (!ecc->write_subpage)
+		if (!ecc->write_subpage && ecc->hwctl && ecc->calculate)
 			ecc->write_subpage = nand_write_subpage_hwecc;
 
 	case NAND_ECC_HW_SYNDROME: