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>
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@ -23,6 +23,13 @@ Required properties:
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integer values for each chip-select line in use:
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0 <physical address of mapping> <size>
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Optional properties:
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- devbus,keep-config This property can optionally be used to keep
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using the timing parameters set by the
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bootloader. It makes all the timing properties
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described below unused.
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Timing properties for child nodes:
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Read parameters:
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@ -31,26 +38,26 @@ Read parameters:
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drive the AD bus after the completion of a device read.
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This prevents contentions on the Device Bus after a read
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cycle from a slow device.
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Mandatory.
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Mandatory, except if devbus,keep-config is used.
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- devbus,bus-width: Defines the bus width, in bits (e.g. <16>).
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Mandatory.
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Mandatory, except if devbus,keep-config is used.
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- devbus,badr-skew-ps: Defines the time delay from from A[2:0] toggle,
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to read data sample. This parameter is useful for
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synchronous pipelined devices, where the address
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precedes the read data by one or two cycles.
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Mandatory.
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Mandatory, except if devbus,keep-config is used.
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- devbus,acc-first-ps: Defines the time delay from the negation of
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ALE[0] to the cycle that the first read data is sampled
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by the controller.
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Mandatory.
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Mandatory, except if devbus,keep-config is used.
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- devbus,acc-next-ps: Defines the time delay between the cycle that
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samples data N and the cycle that samples data N+1
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(in burst accesses).
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Mandatory.
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Mandatory, except if devbus,keep-config is used.
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- devbus,rd-setup-ps: Defines the time delay between DEV_CSn assertion to
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DEV_OEn assertion. If set to 0 (default),
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@ -58,8 +65,8 @@ Read parameters:
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This parameter has no affect on <acc-first-ps> parameter
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(no affect on first data sample). Set <rd-setup-ps>
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to a value smaller than <acc-first-ps>.
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Mandatory for "marvell,mvebu-devbus"
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compatible string, ignored otherwise.
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Mandatory for "marvell,mvebu-devbus" compatible string,
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except if devbus,keep-config is used.
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- devbus,rd-hold-ps: Defines the time between the last data sample to the
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de-assertion of DEV_CSn. If set to 0 (default),
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@ -70,8 +77,8 @@ Read parameters:
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last data sampled. Also this parameter has no
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affect on <turn-off-ps> parameter.
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Set <rd-hold-ps> to a value smaller than <turn-off-ps>.
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Mandatory for "marvell,mvebu-devbus"
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compatible string, ignored otherwise.
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Mandatory for "marvell,mvebu-devbus" compatible string,
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except if devbus,keep-config is used.
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Write parameters:
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@ -96,8 +103,8 @@ Write parameters:
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- devbus,sync-enable: Synchronous device enable.
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1: True
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0: False
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Mandatory for "marvell,mvebu-devbus" compatible
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string, ignored otherwise.
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Mandatory for "marvell,mvebu-devbus" compatible string,
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except if devbus,keep-config is used.
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An example for an Armada XP GP board, with a 16 MiB NOR device as child
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is showed below. Note that the Device Bus driver is in charge of allocating
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@ -310,16 +310,18 @@ static int mvebu_devbus_probe(struct platform_device *pdev)
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dev_dbg(devbus->dev, "Setting timing parameter, tick is %lu ps\n",
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devbus->tick_ps);
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/* Read the Device Tree node */
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err = devbus_get_timing_params(devbus, node, &r, &w);
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if (err < 0)
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return err;
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if (!of_property_read_bool(node, "devbus,keep-config")) {
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/* Read the Device Tree node */
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err = devbus_get_timing_params(devbus, node, &r, &w);
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if (err < 0)
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return err;
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/* Set the new timing parameters */
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if (of_device_is_compatible(node, "marvell,orion-devbus"))
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devbus_orion_set_timing_params(devbus, node, &r, &w);
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else
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devbus_armada_set_timing_params(devbus, node, &r, &w);
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/* Set the new timing parameters */
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if (of_device_is_compatible(node, "marvell,orion-devbus"))
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devbus_orion_set_timing_params(devbus, node, &r, &w);
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else
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devbus_armada_set_timing_params(devbus, node, &r, &w);
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}
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/*
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* We need to create a child device explicitly from here to
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