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Date: Fri, 13 May 2022 23:42:03 +0100 (BST)
From: "Maciej W. Rozycki" <macro@...am.me.uk>
To: Jonathan Corbet <corbet@....net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>
cc: Stephen Rothwell <sfr@...b.auug.org.au>,
Andy Shevchenko <andy.shevchenko@...il.com>,
linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-next@...r.kernel.org
Subject: [PATCH 1/3] Documentation: Move Oxford Semiconductor PCIe (Tornado)
950 to misc-devices
Documentation/tty has been moved to driver-api, which is not suitable
for user documentation, so move the Oxford Semiconductor PCIe (Tornado)
950 description to misc-devices instead.
Signed-off-by: Maciej W. Rozycki <macro@...am.me.uk>
---
Documentation/misc-devices/oxsemi-tornado.rst | 129 ++++++++++++++++++++
Documentation/tty/device_drivers/oxsemi-tornado.rst | 129 --------------------
2 files changed, 129 insertions(+), 129 deletions(-)
linux-doc-oxsemi-tornado-move.diff
Index: linux-macro/Documentation/misc-devices/oxsemi-tornado.rst
===================================================================
--- /dev/null
+++ linux-macro/Documentation/misc-devices/oxsemi-tornado.rst
@@ -0,0 +1,129 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================================================================
+Notes on Oxford Semiconductor PCIe (Tornado) 950 serial port devices
+====================================================================
+
+Oxford Semiconductor PCIe (Tornado) 950 serial port devices are driven
+by a fixed 62.5MHz clock input derived from the 100MHz PCI Express clock.
+
+The baud rate produced by the baud generator is obtained from this input
+frequency by dividing it by the clock prescaler, which can be set to any
+value from 1 to 63.875 in increments of 0.125, and then the usual 16-bit
+divisor is used as with the original 8250, to divide the frequency by a
+value from 1 to 65535. Finally a programmable oversampling rate is used
+that can take any value from 4 to 16 to divide the frequency further and
+determine the actual baud rate used. Baud rates from 15625000bps down
+to 0.933bps can be obtained this way.
+
+By default the oversampling rate is set to 16 and the clock prescaler is
+set to 33.875, meaning that the frequency to be used as the reference
+for the usual 16-bit divisor is 115313.653, which is close enough to the
+frequency of 115200 used by the original 8250 for the same values to be
+used for the divisor to obtain the requested baud rates by software that
+is unaware of the extra clock controls available.
+
+The oversampling rate is programmed with the TCR register and the clock
+prescaler is programmed with the CPR/CPR2 register pair[1][2][3][4].
+To switch away from the default value of 33.875 for the prescaler the
+the enhanced mode has to be explicitly enabled though, by setting bit 4
+of the EFR. In that mode setting bit 7 in the MCR enables the prescaler
+or otherwise it is bypassed as if the value of 1 was used. Additionally
+writing any value to CPR clears CPR2 for compatibility with old software
+written for older conventional PCI Oxford Semiconductor devices that do
+not have the extra prescaler's 9th bit in CPR2, so the CPR/CPR2 register
+pair has to be programmed in the right order.
+
+By using these parameters rates from 15625000bps down to 1bps can be
+obtained, with either exact or highly-accurate actual bit rates for
+standard and many non-standard rates.
+
+Here are the figures for the standard and some non-standard baud rates
+(including those quoted in Oxford Semiconductor documentation), giving
+the requested rate (r), the actual rate yielded (a) and its deviation
+from the requested rate (d), and the values of the oversampling rate
+(tcr), the clock prescaler (cpr) and the divisor (div) produced by the
+new `get_divisor' handler:
+
+r: 15625000, a: 15625000.00, d: 0.0000%, tcr: 4, cpr: 1.000, div: 1
+r: 12500000, a: 12500000.00, d: 0.0000%, tcr: 5, cpr: 1.000, div: 1
+r: 10416666, a: 10416666.67, d: 0.0000%, tcr: 6, cpr: 1.000, div: 1
+r: 8928571, a: 8928571.43, d: 0.0000%, tcr: 7, cpr: 1.000, div: 1
+r: 7812500, a: 7812500.00, d: 0.0000%, tcr: 8, cpr: 1.000, div: 1
+r: 4000000, a: 4000000.00, d: 0.0000%, tcr: 5, cpr: 3.125, div: 1
+r: 3686400, a: 3676470.59, d: -0.2694%, tcr: 8, cpr: 2.125, div: 1
+r: 3500000, a: 3496503.50, d: -0.0999%, tcr: 13, cpr: 1.375, div: 1
+r: 3000000, a: 2976190.48, d: -0.7937%, tcr: 14, cpr: 1.500, div: 1
+r: 2500000, a: 2500000.00, d: 0.0000%, tcr: 10, cpr: 2.500, div: 1
+r: 2000000, a: 2000000.00, d: 0.0000%, tcr: 10, cpr: 3.125, div: 1
+r: 1843200, a: 1838235.29, d: -0.2694%, tcr: 16, cpr: 2.125, div: 1
+r: 1500000, a: 1492537.31, d: -0.4975%, tcr: 5, cpr: 8.375, div: 1
+r: 1152000, a: 1152073.73, d: 0.0064%, tcr: 14, cpr: 3.875, div: 1
+r: 921600, a: 919117.65, d: -0.2694%, tcr: 16, cpr: 2.125, div: 2
+r: 576000, a: 576036.87, d: 0.0064%, tcr: 14, cpr: 3.875, div: 2
+r: 460800, a: 460829.49, d: 0.0064%, tcr: 7, cpr: 3.875, div: 5
+r: 230400, a: 230414.75, d: 0.0064%, tcr: 14, cpr: 3.875, div: 5
+r: 115200, a: 115207.37, d: 0.0064%, tcr: 14, cpr: 1.250, div: 31
+r: 57600, a: 57603.69, d: 0.0064%, tcr: 8, cpr: 3.875, div: 35
+r: 38400, a: 38402.46, d: 0.0064%, tcr: 14, cpr: 3.875, div: 30
+r: 19200, a: 19201.23, d: 0.0064%, tcr: 8, cpr: 3.875, div: 105
+r: 9600, a: 9600.06, d: 0.0006%, tcr: 9, cpr: 1.125, div: 643
+r: 4800, a: 4799.98, d: -0.0004%, tcr: 7, cpr: 2.875, div: 647
+r: 2400, a: 2400.02, d: 0.0008%, tcr: 9, cpr: 2.250, div: 1286
+r: 1200, a: 1200.00, d: 0.0000%, tcr: 14, cpr: 2.875, div: 1294
+r: 300, a: 300.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 7215
+r: 200, a: 200.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 15625
+r: 150, a: 150.00, d: 0.0000%, tcr: 13, cpr: 2.250, div: 14245
+r: 134, a: 134.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 16153
+r: 110, a: 110.00, d: 0.0000%, tcr: 12, cpr: 1.000, div: 47348
+r: 75, a: 75.00, d: 0.0000%, tcr: 4, cpr: 5.875, div: 35461
+r: 50, a: 50.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 62500
+r: 25, a: 25.00, d: 0.0000%, tcr: 16, cpr: 2.500, div: 62500
+r: 4, a: 4.00, d: 0.0000%, tcr: 16, cpr: 20.000, div: 48828
+r: 2, a: 2.00, d: 0.0000%, tcr: 16, cpr: 40.000, div: 48828
+r: 1, a: 1.00, d: 0.0000%, tcr: 16, cpr: 63.875, div: 61154
+
+With the baud base set to 15625000 and the unsigned 16-bit UART_DIV_MAX
+limitation imposed by `serial8250_get_baud_rate' standard baud rates
+below 300bps become unavailable in the regular way, e.g. the rate of
+200bps requires the baud base to be divided by 78125 and that is beyond
+the unsigned 16-bit range. The historic spd_cust feature can still be
+used by encoding the values for, the prescaler, the oversampling rate
+and the clock divisor (DLM/DLL) as follows to obtain such rates if so
+required:
+
+ 31 29 28 20 19 16 15 0
++-----+-----------------+-------+-------------------------------+
+|0 0 0| CPR2:CPR | TCR | DLM:DLL |
++-----+-----------------+-------+-------------------------------+
+
+Use a value such encoded for the `custom_divisor' field along with the
+ASYNC_SPD_CUST flag set in the `flags' field in `struct serial_struct'
+passed with the TIOCSSERIAL ioctl(2), such as with the setserial(8)
+utility and its `divisor' and `spd_cust' parameters, and the select
+the baud rate of 38400bps. Note that the value of 0 in TCR sets the
+oversampling rate to 16 and prescaler values below 1 in CPR2/CPR are
+clamped by the driver to 1.
+
+For example the value of 0x1f4004e2 will set CPR2/CPR, TCR and DLM/DLL
+respectively to 0x1f4, 0x0 and 0x04e2, choosing the prescaler value,
+the oversampling rate and the clock divisor of 62.500, 16 and 1250
+respectively. These parameters will set the baud rate for the serial
+port to 62500000 / 62.500 / 1250 / 16 = 50bps.
+
+References:
+
+[1] "OXPCIe200 PCI Express Multi-Port Bridge", Oxford Semiconductor,
+ Inc., DS-0045, 10 Nov 2008, Section "950 Mode", pp. 64-65
+
+[2] "OXPCIe952 PCI Express Bridge to Dual Serial & Parallel Port",
+ Oxford Semiconductor, Inc., DS-0046, Mar 06 08, Section "950 Mode",
+ p. 20
+
+[3] "OXPCIe954 PCI Express Bridge to Quad Serial Port", Oxford
+ Semiconductor, Inc., DS-0047, Feb 08, Section "950 Mode", p. 20
+
+[4] "OXPCIe958 PCI Express Bridge to Octal Serial Port", Oxford
+ Semiconductor, Inc., DS-0048, Feb 08, Section "950 Mode", p. 20
+
+Maciej W. Rozycki <macro@...am.me.uk>
Index: linux-macro/Documentation/tty/device_drivers/oxsemi-tornado.rst
===================================================================
--- linux-macro.orig/Documentation/tty/device_drivers/oxsemi-tornado.rst
+++ /dev/null
@@ -1,129 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-====================================================================
-Notes on Oxford Semiconductor PCIe (Tornado) 950 serial port devices
-====================================================================
-
-Oxford Semiconductor PCIe (Tornado) 950 serial port devices are driven
-by a fixed 62.5MHz clock input derived from the 100MHz PCI Express clock.
-
-The baud rate produced by the baud generator is obtained from this input
-frequency by dividing it by the clock prescaler, which can be set to any
-value from 1 to 63.875 in increments of 0.125, and then the usual 16-bit
-divisor is used as with the original 8250, to divide the frequency by a
-value from 1 to 65535. Finally a programmable oversampling rate is used
-that can take any value from 4 to 16 to divide the frequency further and
-determine the actual baud rate used. Baud rates from 15625000bps down
-to 0.933bps can be obtained this way.
-
-By default the oversampling rate is set to 16 and the clock prescaler is
-set to 33.875, meaning that the frequency to be used as the reference
-for the usual 16-bit divisor is 115313.653, which is close enough to the
-frequency of 115200 used by the original 8250 for the same values to be
-used for the divisor to obtain the requested baud rates by software that
-is unaware of the extra clock controls available.
-
-The oversampling rate is programmed with the TCR register and the clock
-prescaler is programmed with the CPR/CPR2 register pair[1][2][3][4].
-To switch away from the default value of 33.875 for the prescaler the
-the enhanced mode has to be explicitly enabled though, by setting bit 4
-of the EFR. In that mode setting bit 7 in the MCR enables the prescaler
-or otherwise it is bypassed as if the value of 1 was used. Additionally
-writing any value to CPR clears CPR2 for compatibility with old software
-written for older conventional PCI Oxford Semiconductor devices that do
-not have the extra prescaler's 9th bit in CPR2, so the CPR/CPR2 register
-pair has to be programmed in the right order.
-
-By using these parameters rates from 15625000bps down to 1bps can be
-obtained, with either exact or highly-accurate actual bit rates for
-standard and many non-standard rates.
-
-Here are the figures for the standard and some non-standard baud rates
-(including those quoted in Oxford Semiconductor documentation), giving
-the requested rate (r), the actual rate yielded (a) and its deviation
-from the requested rate (d), and the values of the oversampling rate
-(tcr), the clock prescaler (cpr) and the divisor (div) produced by the
-new `get_divisor' handler:
-
-r: 15625000, a: 15625000.00, d: 0.0000%, tcr: 4, cpr: 1.000, div: 1
-r: 12500000, a: 12500000.00, d: 0.0000%, tcr: 5, cpr: 1.000, div: 1
-r: 10416666, a: 10416666.67, d: 0.0000%, tcr: 6, cpr: 1.000, div: 1
-r: 8928571, a: 8928571.43, d: 0.0000%, tcr: 7, cpr: 1.000, div: 1
-r: 7812500, a: 7812500.00, d: 0.0000%, tcr: 8, cpr: 1.000, div: 1
-r: 4000000, a: 4000000.00, d: 0.0000%, tcr: 5, cpr: 3.125, div: 1
-r: 3686400, a: 3676470.59, d: -0.2694%, tcr: 8, cpr: 2.125, div: 1
-r: 3500000, a: 3496503.50, d: -0.0999%, tcr: 13, cpr: 1.375, div: 1
-r: 3000000, a: 2976190.48, d: -0.7937%, tcr: 14, cpr: 1.500, div: 1
-r: 2500000, a: 2500000.00, d: 0.0000%, tcr: 10, cpr: 2.500, div: 1
-r: 2000000, a: 2000000.00, d: 0.0000%, tcr: 10, cpr: 3.125, div: 1
-r: 1843200, a: 1838235.29, d: -0.2694%, tcr: 16, cpr: 2.125, div: 1
-r: 1500000, a: 1492537.31, d: -0.4975%, tcr: 5, cpr: 8.375, div: 1
-r: 1152000, a: 1152073.73, d: 0.0064%, tcr: 14, cpr: 3.875, div: 1
-r: 921600, a: 919117.65, d: -0.2694%, tcr: 16, cpr: 2.125, div: 2
-r: 576000, a: 576036.87, d: 0.0064%, tcr: 14, cpr: 3.875, div: 2
-r: 460800, a: 460829.49, d: 0.0064%, tcr: 7, cpr: 3.875, div: 5
-r: 230400, a: 230414.75, d: 0.0064%, tcr: 14, cpr: 3.875, div: 5
-r: 115200, a: 115207.37, d: 0.0064%, tcr: 14, cpr: 1.250, div: 31
-r: 57600, a: 57603.69, d: 0.0064%, tcr: 8, cpr: 3.875, div: 35
-r: 38400, a: 38402.46, d: 0.0064%, tcr: 14, cpr: 3.875, div: 30
-r: 19200, a: 19201.23, d: 0.0064%, tcr: 8, cpr: 3.875, div: 105
-r: 9600, a: 9600.06, d: 0.0006%, tcr: 9, cpr: 1.125, div: 643
-r: 4800, a: 4799.98, d: -0.0004%, tcr: 7, cpr: 2.875, div: 647
-r: 2400, a: 2400.02, d: 0.0008%, tcr: 9, cpr: 2.250, div: 1286
-r: 1200, a: 1200.00, d: 0.0000%, tcr: 14, cpr: 2.875, div: 1294
-r: 300, a: 300.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 7215
-r: 200, a: 200.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 15625
-r: 150, a: 150.00, d: 0.0000%, tcr: 13, cpr: 2.250, div: 14245
-r: 134, a: 134.00, d: 0.0000%, tcr: 11, cpr: 2.625, div: 16153
-r: 110, a: 110.00, d: 0.0000%, tcr: 12, cpr: 1.000, div: 47348
-r: 75, a: 75.00, d: 0.0000%, tcr: 4, cpr: 5.875, div: 35461
-r: 50, a: 50.00, d: 0.0000%, tcr: 16, cpr: 1.250, div: 62500
-r: 25, a: 25.00, d: 0.0000%, tcr: 16, cpr: 2.500, div: 62500
-r: 4, a: 4.00, d: 0.0000%, tcr: 16, cpr: 20.000, div: 48828
-r: 2, a: 2.00, d: 0.0000%, tcr: 16, cpr: 40.000, div: 48828
-r: 1, a: 1.00, d: 0.0000%, tcr: 16, cpr: 63.875, div: 61154
-
-With the baud base set to 15625000 and the unsigned 16-bit UART_DIV_MAX
-limitation imposed by `serial8250_get_baud_rate' standard baud rates
-below 300bps become unavailable in the regular way, e.g. the rate of
-200bps requires the baud base to be divided by 78125 and that is beyond
-the unsigned 16-bit range. The historic spd_cust feature can still be
-used by encoding the values for, the prescaler, the oversampling rate
-and the clock divisor (DLM/DLL) as follows to obtain such rates if so
-required:
-
- 31 29 28 20 19 16 15 0
-+-----+-----------------+-------+-------------------------------+
-|0 0 0| CPR2:CPR | TCR | DLM:DLL |
-+-----+-----------------+-------+-------------------------------+
-
-Use a value such encoded for the `custom_divisor' field along with the
-ASYNC_SPD_CUST flag set in the `flags' field in `struct serial_struct'
-passed with the TIOCSSERIAL ioctl(2), such as with the setserial(8)
-utility and its `divisor' and `spd_cust' parameters, and the select
-the baud rate of 38400bps. Note that the value of 0 in TCR sets the
-oversampling rate to 16 and prescaler values below 1 in CPR2/CPR are
-clamped by the driver to 1.
-
-For example the value of 0x1f4004e2 will set CPR2/CPR, TCR and DLM/DLL
-respectively to 0x1f4, 0x0 and 0x04e2, choosing the prescaler value,
-the oversampling rate and the clock divisor of 62.500, 16 and 1250
-respectively. These parameters will set the baud rate for the serial
-port to 62500000 / 62.500 / 1250 / 16 = 50bps.
-
-References:
-
-[1] "OXPCIe200 PCI Express Multi-Port Bridge", Oxford Semiconductor,
- Inc., DS-0045, 10 Nov 2008, Section "950 Mode", pp. 64-65
-
-[2] "OXPCIe952 PCI Express Bridge to Dual Serial & Parallel Port",
- Oxford Semiconductor, Inc., DS-0046, Mar 06 08, Section "950 Mode",
- p. 20
-
-[3] "OXPCIe954 PCI Express Bridge to Quad Serial Port", Oxford
- Semiconductor, Inc., DS-0047, Feb 08, Section "950 Mode", p. 20
-
-[4] "OXPCIe958 PCI Express Bridge to Octal Serial Port", Oxford
- Semiconductor, Inc., DS-0048, Feb 08, Section "950 Mode", p. 20
-
-Maciej W. Rozycki <macro@...am.me.uk>
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