Patch "spi: spi-mem: add statistics support to ->exec_op() calls" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    spi: spi-mem: add statistics support to ->exec_op() calls

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     spi-spi-mem-add-statistics-support-to-exec_op-calls.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 3d62943b0583bf7497f926530f25e6d3389cad5c
Author: Théo Lebrun <theo.lebrun@xxxxxxxxxxx>
Date:   Fri Feb 16 17:42:19 2024 +0100

    spi: spi-mem: add statistics support to ->exec_op() calls
    
    [ Upstream commit e63aef9c9121e5061cbf5112d12cadc9da399692 ]
    
    Current behavior is that spi-mem operations do not increment statistics,
    neither per-controller nor per-device, if ->exec_op() is used. For
    operations that do NOT use ->exec_op(), stats are increased as the
    usual spi_sync() is called.
    
    The newly implemented spi_mem_add_op_stats() function is strongly
    inspired by spi_statistics_add_transfer_stats(); locking logic and
    l2len computation comes from there.
    
    Statistics that are being filled: bytes{,_rx,_tx}, messages, transfers,
    errors, timedout, transfer_bytes_histo_*.
    
    Note about messages & transfers counters: in the fallback to spi_sync()
    case, there are from 1 to 4 transfers per message. We only register one
    big transfer in the ->exec_op() case as that is closer to reality.
    
    This patch is NOT touching:
     - spi_async, spi_sync, spi_sync_immediate: those counters describe
       precise function calls, incrementing them would be lying. I believe
       comparing the messages counter to spi_async+spi_sync is a good way
       to detect ->exec_op() calls, but I might be missing edge cases
       knowledge.
     - transfers_split_maxsize: splitting cannot happen if ->exec_op() is
       provided.
    
    Reviewed-by: Dhruva Gole <d-gole@xxxxxx>
    Signed-off-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx>
    Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
    Link: https://msgid.link/r/20240216-spi-mem-stats-v2-1-9256dfe4887d@xxxxxxxxxxx
    Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
    Stable-dep-of: 29895ce18311 ("spi: Fix error code checking in spi_mem_exec_op()")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 2dc8ceb85374b..c9d6d42a88f55 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c
@@ -297,6 +297,49 @@ static void spi_mem_access_end(struct spi_mem *mem)
 		pm_runtime_put(ctlr->dev.parent);
 }
 
+static void spi_mem_add_op_stats(struct spi_statistics __percpu *pcpu_stats,
+				 const struct spi_mem_op *op, int exec_op_ret)
+{
+	struct spi_statistics *stats;
+	u64 len, l2len;
+
+	get_cpu();
+	stats = this_cpu_ptr(pcpu_stats);
+	u64_stats_update_begin(&stats->syncp);
+
+	/*
+	 * We do not have the concept of messages or transfers. Let's consider
+	 * that one operation is equivalent to one message and one transfer.
+	 */
+	u64_stats_inc(&stats->messages);
+	u64_stats_inc(&stats->transfers);
+
+	/* Use the sum of all lengths as bytes count and histogram value. */
+	len = op->cmd.nbytes + op->addr.nbytes;
+	len += op->dummy.nbytes + op->data.nbytes;
+	u64_stats_add(&stats->bytes, len);
+	l2len = min(fls(len), SPI_STATISTICS_HISTO_SIZE) - 1;
+	u64_stats_inc(&stats->transfer_bytes_histo[l2len]);
+
+	/* Only account for data bytes as transferred bytes. */
+	if (op->data.nbytes && op->data.dir == SPI_MEM_DATA_OUT)
+		u64_stats_add(&stats->bytes_tx, op->data.nbytes);
+	if (op->data.nbytes && op->data.dir == SPI_MEM_DATA_IN)
+		u64_stats_add(&stats->bytes_rx, op->data.nbytes);
+
+	/*
+	 * A timeout is not an error, following the same behavior as
+	 * spi_transfer_one_message().
+	 */
+	if (exec_op_ret == -ETIMEDOUT)
+		u64_stats_inc(&stats->timedout);
+	else if (exec_op_ret)
+		u64_stats_inc(&stats->errors);
+
+	u64_stats_update_end(&stats->syncp);
+	put_cpu();
+}
+
 /**
  * spi_mem_exec_op() - Execute a memory operation
  * @mem: the SPI memory
@@ -339,8 +382,12 @@ int spi_mem_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 		 * read path) and expect the core to use the regular SPI
 		 * interface in other cases.
 		 */
-		if (!ret || ret != -ENOTSUPP || ret != -EOPNOTSUPP)
+		if (!ret || ret != -ENOTSUPP || ret != -EOPNOTSUPP) {
+			spi_mem_add_op_stats(ctlr->pcpu_statistics, op, ret);
+			spi_mem_add_op_stats(mem->spi->pcpu_statistics, op, ret);
+
 			return ret;
+		}
 	}
 
 	tmpbufsize = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;