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  1. 07 Oct, 2016 3 commits
    • Karl Beldan's avatar
      mtd: nand: davinci: Reinitialize the HW ECC engine in 4bit hwctl · ebc9785b
      Karl Beldan authored 
      commit f6d7c1b5 upstream.

This fixes subpage writes when using 4-bit HW ECC.

There has been numerous reports about ECC errors with devices using this
driver for a while.  Also the 4-bit ECC has been reported as broken with
subpages in [1] and with 16 bits NANDs in the driver and in mach* board
files both in mainline and in the vendor BSPs.

What I saw with 4-bit ECC on a 16bits NAND (on an LCDK) which got me to
try reinitializing the ECC engine:
- R/W on whole pages properly generates/checks RS code
- try writing the 1st subpage only of a blank page, the subpage is well
  written and the RS code properly generated, re-reading the same page
  the HW detects some ECC error, reading the same page again no ECC
  error is detected

Note that the ECC engine is already reinitialized in the 1-bit case.

Tested on my LCDK with UBI+UBIFS using subpages.
This could potentially get rid of the issue workarounded in [1].

[1] 28c015a9 ("mtd: davinci-nand: disable subpage write for keystone-nand")

Fixes: 6a4123e5 ("mtd: nand: davinci_nand, 4-bit ECC for smallpage")
Signed-off-by: default avatarKarl Beldan <kbeldan@baylibre.com>
Acked-by: default avatarBoris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      ebc9785b
    • Michael Ellerman's avatar
      powerpc: Add macros for the ibm_architecture_vec[] lengths · 9dcc5e15
      Michael Ellerman authored 
      commit e8a4fd0a upstream.

The encoding of the lengths in the ibm_architecture_vec array is
"interesting" to say the least. It's non-obvious how the number of bytes
we provide relates to the length value.

In fact we already got it wrong once, see 11e9ed43 "Fix up
ibm_architecture_vec definition".

So add some macros to make it (hopefully) clearer. These at least have
the property that the integer present in the code is equal to the number
of bytes that follows it.
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: default avatarStewart Smith <stewart@linux.vnet.ibm.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      9dcc5e15
    • Peter Zijlstra's avatar
      sched/core: Fix an SMP ordering race in try_to_wake_up() vs. schedule() · ac080ae1
      Peter Zijlstra authored 
      commit ecf7d01c upstream.

Oleg noticed that its possible to falsely observe p->on_cpu == 0 such
that we'll prematurely continue with the wakeup and effectively run p on
two CPUs at the same time.

Even though the overlap is very limited; the task is in the middle of
being scheduled out; it could still result in corruption of the
scheduler data structures.

        CPU0                            CPU1

        set_current_state(...)

        <preempt_schedule>
          context_switch(X, Y)
            prepare_lock_switch(Y)
              Y->on_cpu = 1;
            finish_lock_switch(X)
              store_release(X->on_cpu, 0);

                                        try_to_wake_up(X)
                                          LOCK(p->pi_lock);

                                          t = X->on_cpu; // 0

          context_switch(Y, X)
            prepare_lock_switch(X)
              X->on_cpu = 1;
            finish_lock_switch(Y)
              store_release(Y->on_cpu, 0);
        </preempt_schedule>

        schedule();
          deactivate_task(X);
          X->on_rq = 0;

                                          if (X->on_rq) // false

                                          if (t) while (X->on_cpu)
                                            cpu_relax();

          context_switch(X, ..)
            finish_lock_switch(X)
              store_release(X->on_cpu, 0);

Avoid the load of X->on_cpu being hoisted over the X->on_rq load.
Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      ac080ae1
  3. 06 Oct, 2016 34 commits
  5. 29 Sep, 2016 3 commits
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