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    Subject[PATCH 4.4 42/97] powerpc/powernv: Fix OPAL NVRAM driver OPAL_BUSY loops
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Nicholas Piggin <npiggin@gmail.com>

    commit 3b8070335f751aac9f1526ae2e012e6f5b8b0f21 upstream.

    The OPAL NVRAM driver does not sleep in case it gets OPAL_BUSY or
    OPAL_BUSY_EVENT from firmware, which causes large scheduling
    latencies, and various lockup errors to trigger (again, BMC reboot
    can cause it).

    Fix this by converting it to the standard form OPAL_BUSY loop that
    sleeps.

    Fixes: 628daa8d5abf ("powerpc/powernv: Add RTC and NVRAM support plus RTAS fallbacks")
    Depends-on: 34dd25de9fe3 ("powerpc/powernv: define a standard delay for OPAL_BUSY type retry loops")
    Cc: stable@vger.kernel.org # v3.2+
    Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/powerpc/platforms/powernv/opal-nvram.c | 7 ++++++-
    1 file changed, 6 insertions(+), 1 deletion(-)

    --- a/arch/powerpc/platforms/powernv/opal-nvram.c
    +++ b/arch/powerpc/platforms/powernv/opal-nvram.c
    @@ -11,6 +11,7 @@

    #define DEBUG

    +#include <linux/delay.h>
    #include <linux/kernel.h>
    #include <linux/init.h>
    #include <linux/of.h>
    @@ -56,8 +57,12 @@ static ssize_t opal_nvram_write(char *bu

    while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
    rc = opal_write_nvram(__pa(buf), count, off);
    - if (rc == OPAL_BUSY_EVENT)
    + if (rc == OPAL_BUSY_EVENT) {
    + msleep(OPAL_BUSY_DELAY_MS);
    opal_poll_events(NULL);
    + } else if (rc == OPAL_BUSY) {
    + msleep(OPAL_BUSY_DELAY_MS);
    + }
    }

    if (rc)

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