staging: comedi: fix minimum AO period for NI 625x and NI 628x

commit 34b55d8c48f4f76044d8f4d6ec3dc786cf210312 upstream.

The minimum period was set to 357 ns, while the divider for these boards is 50
ns. This prevented to output at maximum speed as ni_ao_cmdtest() would return
357 but would not accept it.

Not sure why it was set to 357 ns (this was done before the git history,
which starts 5 years ago). My guess is that it comes from reading the
specification stating a 2.8 MHz rate (~ 357 ns). The latest
specification states a 2.86 MHz rate (~ 350 ns), which makes a lot
more sense.

Tested on a pci-6251.

Signed-off-by: Éric Piel <piel@delmic.com>
Acked-By: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: drop hunk for a board that's not listed]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/staging/comedi/drivers/ni_pcimio.c b/drivers/staging/comedi/drivers/ni_pcimio.c
index 9148abdad07468d03ae251032d3c2481b99f8ffd..9fee2f2f38b6b2eece7a82ed715707f19b2a11d5 100644 (file)
--- a/drivers/staging/comedi/drivers/ni_pcimio.c
+++ b/drivers/staging/comedi/drivers/ni_pcimio.c
@@ -1021,7 +1021,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_625x_ao,
         .reg_type = ni_reg_625x,
         .ao_unipolar = 0,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 8,
         .caldac = {caldac_none},
         .has_8255 = 0,
@@ -1040,7 +1040,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_625x_ao,
         .reg_type = ni_reg_625x,
         .ao_unipolar = 0,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 8,
         .caldac = {caldac_none},
         .has_8255 = 0,
@@ -1076,7 +1076,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_625x_ao,
         .reg_type = ni_reg_625x,
         .ao_unipolar = 0,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 32,
         .caldac = {caldac_none},
         .has_8255 = 0,
@@ -1095,7 +1095,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_625x_ao,
         .reg_type = ni_reg_625x,
         .ao_unipolar = 0,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 32,
         .caldac = {caldac_none},
         .has_8255 = 0,
@@ -1131,7 +1131,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_628x_ao,
         .reg_type = ni_reg_628x,
         .ao_unipolar = 1,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 8,
         .caldac = {caldac_none},
         .has_8255 = 0,
@@ -1150,7 +1150,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_628x_ao,
         .reg_type = ni_reg_628x,
         .ao_unipolar = 1,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 8,
         .caldac = {caldac_none},
         .has_8255 = 0,
@@ -1186,7 +1186,7 @@ static const struct ni_board_struct ni_boards[] = {
         .ao_range_table = &range_ni_M_628x_ao,
         .reg_type = ni_reg_628x,
         .ao_unipolar = 1,
-        .ao_speed = 357,
+        .ao_speed = 350,
         .num_p0_dio_channels = 32,
         .caldac = {caldac_none},
         .has_8255 = 0,