On Mon, 2012-07-16 at 12:55 +0200, Guennadi Liakhovetski wrote: > On Mon, 16 Jul 2012, Vinod Koul wrote: > > > On Mon, 2012-07-16 at 12:01 +0200, Guennadi Liakhovetski wrote: > > > On Mon, 16 Jul 2012, Vinod Koul wrote: > > > > > > > On Mon, 2012-07-16 at 10:47 +0200, Guennadi Liakhovetski wrote: > > > > > > I want to know what does ccr and mid_rid mean to dmac here? > > > > > > > > > > CHCR contains a few fields, some enable various interrupt sources, > > > > > some > > > > > specify repeat- and renew-modes, others yet specify transfer size, > > > > > source > > > > > and destination address-modes (incrementing, constant, decrementing), > > > > > others yet select a DMA client category (slave / memcpy / ...), and a > > > > > transfer flag. Some of these fields could be calculated, others are > > > > > pre-defined for various slaves, the exact layout of those fields can > > > > > also > > > > > vary between SoCs. > > > > I do not understand how clients would provide these values. > > > > For pre-defined values, they should be dmac property why should client > > > > like spi or mmc have clue about it? > > > > > > > > For others like you mentioned, i guess they could be easily calculated, > > > > right? > > > > > > > > > MID_RID is actually a slave-selector, it contains a magic value, that > > > > > cannot be calculated. > > > > and again, how does client know this? > > > > > > I might be misunderstanding you, but from earlier discussions I got an > > > impression, that the DMAC should know nothing about clients, i.e., should > > > receive no client-specific information from its platform data. Instead > > > clients should provide it when configuring the channel. If this is > > > correct, then the preferred way would be to specify these values in > > > client > > > platform data and then pass it to the DMAC with slave-config calls? Or > > > have I misunderstood you and this per-client information should be kept > > > in > > > DMAC platform data? > > You haven't misunderstood me. dmacs should not know of client data and > > should be client agnostic. > > > > BUT, are these parameters ccr and mid_rid client data, i do not think > > so, they seem to be dmac controller parameters which you need to > > configure channel or is that not the case. If not why bother passing > > them to dmac? > > Yes, that's right - these values have to be written to DMAC channel > configuration registers, so, we do not have to change anything, those > values can remain DMAC parameters and be passed to it directly from > platform data. Can you get that in future fixes. > > > Either way something looks fishy to me. > > You can always tell me what you don't like about the driver, but I don't > see why this specific patch should cause any problem - it only changes the > type of the slave-id variable from unsigned to signed to be able to pass > negative error values in it too. This question was not specific to this patchset
Btw I am quite happy with this patchset. Good direction for this and thanks for taking it up. -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
