Subject: [PATCHv3 2/8] mailbox/omap: add support for parsing dt devices

From: [email-masked] (Suman Anna)
Date: Wed, 7 Aug 2013 11:59:08 -0500

Kumar,

>> Logic has been added to the OMAP2+ mailbox code to
>> parse the mailbox dt nodes and construct the different
>> mailboxes associated with the instance. The design is
>> based on gathering the same information that was being
>> passed previously through the platform data, except for
>> the interrupt type configuration information.
>>
>> Signed-off-by: Suman Anna <[email-masked]>
>> ---
>> .../devicetree/bindings/mailbox/omap-mailbox.txt   |  43 +++++++
>> drivers/mailbox/mailbox-omap2.c                    | 130 ++++++++++++++++++---
>> 2 files changed, 158 insertions(+), 15 deletions(-)
>> create mode 100644 Documentation/devicetree/bindings/mailbox/omap-mailbox.txt
>>
>> diff --git a/Documentation/devicetree/bindings/mailbox/omap-mailbox.txt b/Documentation/devicetree/bindings/mailbox/omap-mailbox.txt
>> new file mode 100644
>> index 0000000..8ffb08a
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/mailbox/omap-mailbox.txt
>> @@ -0,0 +1,43 @@
>> +OMAP2+ Mailbox Driver
>> +
>> +Required properties:
>> +- compatible:		Should be one of the following,
>> +			    "ti,omap2-mailbox" for
>> +				OMAP2420, OMAP2430, OMAP3430, OMAP3630 SoCs
>> +			    "ti,omap4-mailbox" for
>> +				OMAP44xx, OMAP54xx, AM33xx, AM43xx, DRA7xx SoCs
>> +- reg:			Contains the mailbox register address range (base address
>> +			and length)
>> +- interrupts: 		Contains the interrupt information for the mailbox
>> +			device. The format is dependent on which interrupt
>> +			controller the OMAP device uses
>> +- ti,hwmods:		Name of the hwmod associated with the mailbox
>> +- ti,mbox-num-users:	Number of targets (processor devices) that the mailbox device
>> +			can interrupt
>> +- ti,mbox-num-fifos:	Number of h/w fifos within the mailbox device
> 
> Isn't "ti,mbox-num-users", "ti,mbox-num-fifos" this SoC specific, why do we need to encode in the device tree.  Can we not have a more SoC specific compatiable and encode such info in the driver as part of the .data field in of_device_id ?

They are IP design parameters for the number of h/w fifos and interrupts
coming out of the IP block, with the functionality identical. This
information could not be read from any registers. Until OMAP5, we always
had a single IP in the SoC and so these could been encoded in the
driver. But in DRA7xx, a new SoC, we have 13 mailboxes which have
differing number of these properties even though the functional IP block
is same.

> 
>> +- ti,mbox-names:	Array of the names of the mailboxes
>> +- ti,mbox-data:		Mailbox descriptor data private to each mailbox. The 4
>> +			cells represent the following data,
>> +			  Cell #1 (tx_id) - mailbox fifo id used for
>> +						transmitting messages
>> +			  Cell #2 (rx_id) - mailbox fifo id on which messages
>> +						are received
>> +			  Cell #3 (irq_id) - irq identifier index number to use
>> +						from the interrupts data
>> +			  Cell #4 (usr_id) - mailbox user id for identifying the
>> +						interrupt into the MPU interrupt
>> +						controller.
>> +
> 
> ti,mbox-data really seems like it should be encoded in the driver and not in the device tree.  Is it specific to the SoC?

The mbox-data represents the assignment of h/w fifos between a pair of
processors on an SoC, so it is specific to a mailbox IP instance in an
SoC. Also, this assignment makes it flexible for anyone wishing to use
their own firmware/stack on the remote processor side if using different
h/w fifo combination.

So, a single SoC-specific compatible string would not be enough to
identify either of the above data in the driver.

regards
Suman

> 
>> +Example:
>> +
>> +/* OMAP4 */
>> +mailbox: mailbox at 4a0f4000 {
>> +	compatible = "ti,omap4-mailbox";
>> +	reg = <0x4a0f4000 0x200>;
>> +	interrupts = <GIC_SPI 47 IRQ_TYPE_LEVEL_HIGH>;
>> +	ti,hwmods = "mailbox";
>> +	ti,mbox-num-users = <3>;
>> +	ti,mbox-num-fifos = <8>;
>> +	ti,mbox-names = "mbox-ipu", "mbox-dsp";
>> +	ti,mbox-data = <0 1 0 0>, <3 2 0 0>;
>> +};
> 
> [snip]
> 
> - k
> 
> --
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
>