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    SubjectRe: [PATCH v2 01/24] EDAC, mc: Fix grain_bits calculation
    On Mon, Jun 24, 2019 at 03:08:55PM +0000, Robert Richter wrote:
    > The grain in edac is defined as "minimum granularity for an error
    > report, in bytes". The following calculation of the grain_bits in
    > edac_mc is wrong:
    >
    > grain_bits = fls_long(e->grain) + 1;
    >
    > Where grain_bits is defined as:
    >
    > grain = 1 << grain_bits
    >
    > Example:
    >
    > grain = 8 # 64 bit (8 bytes)
    > grain_bits = fls_long(8) + 1
    > grain_bits = 4 + 1 = 5
    >
    > grain = 1 << grain_bits
    > grain = 1 << 5 = 32
    >
    > Replacing it with the correct calculation:
    >
    > grain_bits = fls_long(e->grain - 1);
    >
    > The example gives now:
    >
    > grain_bits = fls_long(8 - 1)
    > grain_bits = fls_long(8 - 1)
    > grain_bits = 3
    >
    > grain = 1 << 3 = 8
    >
    > Note: We need to check if the hardware reports a reasonable grain != 0
    > and fallback with a warn_once and 1 byte granularity otherwise.
    >
    > Signed-off-by: Robert Richter <rrichter@marvell.com>
    > ---
    > drivers/edac/edac_mc.c | 10 ++++++++--
    > 1 file changed, 8 insertions(+), 2 deletions(-)

    Applied to the new EDAC repo:

    https://git.kernel.org/pub/scm/linux/kernel/git/ras/ras.git/log/?h=edac-for-next

    Thx.

    --
    Regards/Gruss,
    Boris.

    Good mailing practices for 400: avoid top-posting and trim the reply.

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