On Mon Nov 14, 2022 at 3:53 AM IST, Vinod Koul wrote: > On 11-11-22, 10:42, Sireesh Kodali wrote: > > On Fri Nov 4, 2022 at 6:10 PM IST, Vinod Koul wrote: > > > On 27-10-22, 10:44, Sireesh Kodali wrote: > > > > The IPA v2.x block, found on some older Qualcomm SoCs, uses BAM DMA to > > > > send and receive packets from the AP. It also uses BAM to receive > > > > commands from the AP (and possibly the modem). These commands are > > > > encoded as "Immediate Commands". They vary from regular BAM DMA > > > > commands. Adding support for immediate commands is trivial, but requires > > > > also adding Immediate Commands to the dmaengine API, which is what this > > > > patch series does. > > > > > > Can you explain a bit more. I understand you need "Immediate Commands" > > > but am really reluctant to add another interface to support a specific > > > use case > > > > > > > Apologies for the delayed response > > > > BAM supports both regular commands, and "immediate commands". Currently, > > commands are used by the Qualcom NAND chip driver, while "immediate > > commands" are intended to be used by the (yet to be mainlined) IPA > > driver. From the BAM driver perspective, both immediate and regular > > commands are simply a matter of setting the appropriate flag in the > > descriptor. I don't have access to the documentation on BAM to know > > exactly how these two modes differ, however I do know they are not > > interchangable. If a different API is suggested, I can change the > > implementation as needed. > > Ok, can you please explain what is meant by 'regular' cmd and > 'immediate', lets see what is required here Stephan pointed out the APQ8016E TRM has details on BAM. As I understand it, 'regular' commands are queued register read/writes for the peripheral. Immediate commands on the other hand seem to be interpreted by the peripheral's firmware, and don't involve any register writes/reads from BAM's perspective. This is what the TRM has to say: > Immediate (IMM) (only for BAM-NDP): Allows the software to create > descriptors of type immediate, which does not generate any data > transmissions or registers configuration, it is simply supplied to the > peripheral, the peripheral then parses its fields (which are > irrelevant to the BAM). Only the flags of this descriptor are relevant > to the BAM, address and size are irrelevant, and BAM simply passes > them as is to the peripheral. This can be used for the software to > operate peripheral-specific operations within regular data operations. > Immediate descriptors are published on the sidebands as 1 byte size > descriptor, once BAM_NDP fetches an immediate descriptor, it publishes > all recently fetched descriptors including the immediate descriptor > with immediate indication, to inform the peripheral that the last > published descriptor was immediate descriptor. > Command (CMD) (only for BAM-lite and BAM-NDP): Allows the software to > create descriptors of type command. Descriptors of type command do not > generate any data transmissions but configure registers in the > peripheral (write and read registers operations) Regards, Sireesh > > -- > ~Vinod
