mfd: cros ec: spi: Increase EC transaction delay

50 us is not a long enough delay between EC transactions. At least 70 us are needed for the 16 MHz STM32L part. Increase the delay to 200 us for an extra safety margin. Reviewed-by: Randall Spangler <[email protected]> Signed-off-by: Derek Basehore <[email protected]> Signed-off-by: Thierry Reding <[email protected]> Signed-off-by: Lee Jones <[email protected]>
cbmeeks · Jan 6, 2014 · 49f91ac · 49f91ac
1 parent 9981a31
commit 49f91ac
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
@@ -50,10 +50,11 @@
 /*
   * Time between raising the SPI chip select (for the end of a
   * transaction) and dropping it again (for the next transaction).
-  * If we go too fast, the EC will miss the transaction. It seems
-  * that 50us is enough with the 16MHz STM32 EC.
+  * If we go too fast, the EC will miss the transaction. We know that we
+  * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
+  * safe.
   */
-#define EC_SPI_RECOVERY_TIME_NS	(50 * 1000)
+#define EC_SPI_RECOVERY_TIME_NS	(200 * 1000)
 
 /**
  * struct cros_ec_spi - information about a SPI-connected EC