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memory: mvebu-devbus: add a devbus, keep-config property 

Currently, the mvebu-devbus Device Tree binding makes defining the
timing parameters mandatory.

However, in practice, when converting Orion5x platforms to the Device
Tree, we may not necessarily have easy access to the hardware
platforms to fetch those values which were not defined in old-style
board files: all these platforms rely on the bootloader setting the
timing parameters correctly.

In order to facilitate the migration to the Device Tree of this
platform, this commit relaxes the mvebu-devbus Device Tree binding by
introducing a 'devbus,keep-config' boolean property, which, if
defined, will ignore all timing parameters passed in the Device Tree,
and simply rely on the timing values already defined by the
bootloader.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Link: https://lkml.kernel.org/r/1398202002-28530-10-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>
This commit is contained in:
Thomas Petazzoni 2014-04-22 23:26:13 +02:00 committed by Jason Cooper
parent c4ec7430c3
commit 0456d3300e
2 changed files with 29 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
Documentation/devicetree/bindings/memory-controllers/mvebu-devbus.txt
View File

@ -23,6 +23,13 @@ Required properties:
integer values for each chip-select line in use:
0 <physical address of mapping> <size>
Optional properties:
- devbus,keep-config This property can optionally be used to keep
using the timing parameters set by the
bootloader. It makes all the timing properties
described below unused.
Timing properties for child nodes:
Read parameters:
@ -31,26 +38,26 @@ Read parameters:
drive the AD bus after the completion of a device read.
This prevents contentions on the Device Bus after a read
cycle from a slow device.
Mandatory.
Mandatory, except if devbus,keep-config is used.
- devbus,bus-width: Defines the bus width, in bits (e.g. <16>).
Mandatory.
Mandatory, except if devbus,keep-config is used.
- devbus,badr-skew-ps: Defines the time delay from from A[2:0] toggle,
to read data sample. This parameter is useful for
synchronous pipelined devices, where the address
precedes the read data by one or two cycles.
Mandatory.
Mandatory, except if devbus,keep-config is used.
- devbus,acc-first-ps: Defines the time delay from the negation of
ALE[0] to the cycle that the first read data is sampled
by the controller.
Mandatory.
Mandatory, except if devbus,keep-config is used.
- devbus,acc-next-ps: Defines the time delay between the cycle that
samples data N and the cycle that samples data N+1
(in burst accesses).
Mandatory.
Mandatory, except if devbus,keep-config is used.
- devbus,rd-setup-ps: Defines the time delay between DEV_CSn assertion to
DEV_OEn assertion. If set to 0 (default),
@ -58,8 +65,8 @@ Read parameters:
This parameter has no affect on <acc-first-ps> parameter
(no affect on first data sample). Set <rd-setup-ps>
to a value smaller than <acc-first-ps>.
Mandatory for "marvell,mvebu-devbus"
compatible string, ignored otherwise.
Mandatory for "marvell,mvebu-devbus" compatible string,
except if devbus,keep-config is used.
- devbus,rd-hold-ps: Defines the time between the last data sample to the
de-assertion of DEV_CSn. If set to 0 (default),
@ -70,8 +77,8 @@ Read parameters:
last data sampled. Also this parameter has no
affect on <turn-off-ps> parameter.
Set <rd-hold-ps> to a value smaller than <turn-off-ps>.
Mandatory for "marvell,mvebu-devbus"
compatible string, ignored otherwise.
Mandatory for "marvell,mvebu-devbus" compatible string,
except if devbus,keep-config is used.
Write parameters:
@ -96,8 +103,8 @@ Write parameters:
- devbus,sync-enable: Synchronous device enable.
1: True
0: False
Mandatory for "marvell,mvebu-devbus" compatible
string, ignored otherwise.
Mandatory for "marvell,mvebu-devbus" compatible string,
except if devbus,keep-config is used.
An example for an Armada XP GP board, with a 16 MiB NOR device as child
is showed below. Note that the Device Bus driver is in charge of allocating

20
drivers/memory/mvebu-devbus.c
View File

@ -310,16 +310,18 @@ static int mvebu_devbus_probe(struct platform_device *pdev)
dev_dbg(devbus->dev, "Setting timing parameter, tick is %lu ps\n",
devbus->tick_ps);
/* Read the Device Tree node */
err = devbus_get_timing_params(devbus, node, &r, &w);
if (err < 0)
return err;
if (!of_property_read_bool(node, "devbus,keep-config")) {
/* Read the Device Tree node */
err = devbus_get_timing_params(devbus, node, &r, &w);
if (err < 0)
return err;
/* Set the new timing parameters */
if (of_device_is_compatible(node, "marvell,orion-devbus"))
devbus_orion_set_timing_params(devbus, node, &r, &w);
else
devbus_armada_set_timing_params(devbus, node, &r, &w);
/* Set the new timing parameters */
if (of_device_is_compatible(node, "marvell,orion-devbus"))
devbus_orion_set_timing_params(devbus, node, &r, &w);
else
devbus_armada_set_timing_params(devbus, node, &r, &w);
}
/*
* We need to create a child device explicitly from here to