Messages in this thread Patch in this message | | | From | Robert Richter <> | Subject | [PATCH v2 01/24] EDAC, mc: Fix grain_bits calculation | Date | Mon, 24 Jun 2019 15:08:55 +0000 |
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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(-)
diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c index 64922c8fa7e3..45cac74ab833 100644 --- a/drivers/edac/edac_mc.c +++ b/drivers/edac/edac_mc.c @@ -1235,9 +1235,15 @@ void edac_mc_handle_error(const enum hw_event_mc_err_type type, if (p > e->location) *(p - 1) = '\0'; - /* Report the error via the trace interface */ - grain_bits = fls_long(e->grain) + 1; + /* + * We expect the hw to report a reasonable grain, fallback to + * 1 byte granularity otherwise. + */ + if (WARN_ON_ONCE(!e->grain)) + e->grain = 1; + grain_bits = fls_long(e->grain - 1); + /* Report the error via the trace interface */ if (IS_ENABLED(CONFIG_RAS)) trace_mc_event(type, e->msg, e->label, e->error_count, mci->mc_idx, e->top_layer, e->mid_layer, -- 2.20.1
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