linux-kernel - [ 023/128] staging: comedi: fix minimum AO period for NI 625x and NI 628x

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Message-Id: <20130203144646.088008213@decadent.org.uk>
Date:	Sun, 03 Feb 2013 15:47:07 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org,
	Éric Piel <piel@...mic.com>,
	Ian Abbott <abbotti@....co.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [ 023/128] staging: comedi: fix minimum AO period for NI 625x and NI 628x

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Éric Piel <piel@...mic.com>

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@...mic.com>
Acked-By: Ian Abbott <abbotti@....co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.2: drop hunk for a board that's not listed]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- 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_b
 	 .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_b
 	 .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_b
 	 .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_b
 	 .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_b
 	 .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_b
 	 .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_b
 	 .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,


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