diff --git a/drivers/ata/pata_hpt37x.c b/drivers/ata/pata_hpt37x.c
index 9b191763e6e5..228dc1a8992f 100644
--- a/drivers/ata/pata_hpt37x.c
+++ b/drivers/ata/pata_hpt37x.c
@@ -39,25 +39,24 @@ struct hpt_chip {
 
 /* key for bus clock timings
  * bit
- * 0:3    data_high_time. inactive time of DIOW_/DIOR_ for PIO and MW
- *        DMA. cycles = value + 1
- * 4:8    data_low_time. active time of DIOW_/DIOR_ for PIO and MW
- *        DMA. cycles = value + 1
- * 9:12   cmd_high_time. inactive time of DIOW_/DIOR_ during task file
+ * 0:3    data_high_time. Inactive time of DIOW_/DIOR_ for PIO and MW DMA.
+ *        cycles = value + 1
+ * 4:8    data_low_time. Active time of DIOW_/DIOR_ for PIO and MW DMA.
+ *        cycles = value + 1
+ * 9:12   cmd_high_time. Inactive time of DIOW_/DIOR_ during task file
  *        register access.
- * 13:17  cmd_low_time. active time of DIOW_/DIOR_ during task file
+ * 13:17  cmd_low_time. Active time of DIOW_/DIOR_ during task file
  *        register access.
- * 18:21  udma_cycle_time. clock freq and clock cycles for UDMA xfer.
- *        during task file register access.
- * 22:24  pre_high_time. time to initialize 1st cycle for PIO and MW DMA
- *        xfer.
- * 25:27  cmd_pre_high_time. time to initialize 1st PIO cycle for task
+ * 18:20  udma_cycle_time. Clock cycles for UDMA xfer.
+ * 21     CLK frequency for UDMA: 0=ATA clock, 1=dual ATA clock.
+ * 22:24  pre_high_time. Time to initialize 1st cycle for PIO and MW DMA xfer.
+ * 25:27  cmd_pre_high_time. Time to initialize 1st PIO cycle for task file
  *        register access.
- * 28     UDMA enable
- * 29     DMA enable
- * 30     PIO_MST enable. if set, the chip is in bus master mode during
- *        PIO.
- * 31     FIFO enable.
+ * 28     UDMA enable.
+ * 29     DMA  enable.
+ * 30     PIO_MST enable. If set, the chip is in bus master mode during
+ *        PIO xfer.
+ * 31     FIFO enable. Only for PIO.
  */
 
 static struct hpt_clock hpt37x_timings_33[] = {
diff --git a/drivers/ata/pata_hpt3x2n.c b/drivers/ata/pata_hpt3x2n.c
index b131c8f824d7..4a291221f277 100644
--- a/drivers/ata/pata_hpt3x2n.c
+++ b/drivers/ata/pata_hpt3x2n.c
@@ -45,25 +45,24 @@ struct hpt_chip {
 
 /* key for bus clock timings
  * bit
- * 0:3    data_high_time. inactive time of DIOW_/DIOR_ for PIO and MW
- *        DMA. cycles = value + 1
- * 4:8    data_low_time. active time of DIOW_/DIOR_ for PIO and MW
- *        DMA. cycles = value + 1
- * 9:12   cmd_high_time. inactive time of DIOW_/DIOR_ during task file
+ * 0:3    data_high_time. Inactive time of DIOW_/DIOR_ for PIO and MW DMA.
+ *        cycles = value + 1
+ * 4:8    data_low_time. Active time of DIOW_/DIOR_ for PIO and MW DMA.
+ *        cycles = value + 1
+ * 9:12   cmd_high_time. Inactive time of DIOW_/DIOR_ during task file
  *        register access.
- * 13:17  cmd_low_time. active time of DIOW_/DIOR_ during task file
+ * 13:17  cmd_low_time. Active time of DIOW_/DIOR_ during task file
  *        register access.
- * 18:21  udma_cycle_time. clock freq and clock cycles for UDMA xfer.
- *        during task file register access.
- * 22:24  pre_high_time. time to initialize 1st cycle for PIO and MW DMA
- *        xfer.
- * 25:27  cmd_pre_high_time. time to initialize 1st PIO cycle for task
+ * 18:20  udma_cycle_time. Clock cycles for UDMA xfer.
+ * 21     CLK frequency for UDMA: 0=ATA clock, 1=dual ATA clock.
+ * 22:24  pre_high_time. Time to initialize 1st cycle for PIO and MW DMA xfer.
+ * 25:27  cmd_pre_high_time. Time to initialize 1st PIO cycle for task file
  *        register access.
- * 28     UDMA enable
- * 29     DMA enable
- * 30     PIO_MST enable. if set, the chip is in bus master mode during
- *        PIO.
- * 31     FIFO enable.
+ * 28     UDMA enable.
+ * 29     DMA  enable.
+ * 30     PIO_MST enable. If set, the chip is in bus master mode during
+ *        PIO xfer.
+ * 31     FIFO enable. Only for PIO.
  */
 
 /* 66MHz DPLL clocks */