Messages in this thread | | | Date | Fri, 21 Feb 2014 11:36:27 -0600 | From | Joel Fernandes <> | Subject | Re: [PATCH] ARM: EDMA: Use platform_get_resource functions for DT |
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On 02/21/2014 06:15 AM, Mark Rutland wrote: >> Also, while at it get rid of the assumption in the code that "CC" is at reg >> index 0 in the DT and xbar is at offset 1. Instead use reg-names to get the >> memory resource in concern keeping things much cleaner and simpler. This also >> makes it possible to have multiple channel controllers. > > While this is nice I think we have to have a fallback to the existing > behaviour if there's no reg-names property present, unless we know for > certain no-one is possibly using an existing DTB.
Yes, its true it break existing DTBs but currently only 2 TI SoCs use EDMA this way, the vast majority of EDMA users are yet to follow where we can do it right. Further, the old bindings are really limiting specially the 2 CC case and if additionally memory maps are used in the future. So keeping the old binding is limiting in this regard.
Here is what the platform_data used to look like when used by mach-davinci:
static struct resource da850_edma_resources[] = { { .name = "edma_cc0", .start = DA8XX_TPCC_BASE, .end = DA8XX_TPCC_BASE + SZ_32K - 1, .flags = IORESOURCE_MEM, }, { .name = "edma_tc0", .start = DA8XX_TPTC0_BASE, .end = DA8XX_TPTC0_BASE + SZ_1K - 1, .flags = IORESOURCE_MEM, }, { .name = "edma_tc1", .start = DA8XX_TPTC1_BASE, .end = DA8XX_TPTC1_BASE + SZ_1K - 1, .flags = IORESOURCE_MEM, }, { .name = "edma_cc1", .start = DA850_TPCC1_BASE, .end = DA850_TPCC1_BASE + SZ_32K - 1, .flags = IORESOURCE_MEM, },
As you can see, there are several memory maps and different interpretations. Considering this, IMO- it makes sense to pay a small price to keep the semantics sane.
On the other hand, the other 2 options are: 1. We add a fallback if reg-names look up fails. 2. We inject reg-names property into edma DT nodes that don't have them, and make sure all future dtsi with edma nodes mention the reg-names property.
These 2 are a bit error prone though, for example if someone deliberately forgets to mention reg-names, and the code still works, but misbehaves in some way.
Regards, -Joel
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