* Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [090109 15:22]: > > -----Original Message----- > > From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] > > Sent: Friday, January 09, 2009 6:27 PM > > To: Shilimkar, Santosh > > Cc: Pandita, Vikram; linux-omap@xxxxxxxxxxxxxxx > > Subject: Re: [PATCH] [OMAPZOOM] OMAP : DMA: Spurious interrupt fix > > > > * Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [090109 14:52]: > > > > -----Original Message----- > > > > From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] > > > > Sent: Friday, January 09, 2009 4:58 PM > > > > To: Shilimkar, Santosh > > > > Cc: Pandita, Vikram; linux-omap@xxxxxxxxxxxxxxx > > > > Subject: Re: [PATCH] [OMAPZOOM] OMAP : DMA: Spurious interrupt fix > > > > > > > > * Shilimkar, Santosh <santosh.shilimkar@xxxxxx> [090109 12:51]: > > > > > > > > > > Tony, > > > > > Regarding your proposal of doing the no. of channel > > > > reservation during runtime has one problem. > > > > > > > > > > The whole idea was not to restrict users from using all 32 > > > > channels and hence the config option. For OMAP secure chips, > > > > few security drivers which will execute in secure contex > > > > needs dedicated DMA channels and kernel dma library can't be > > > > used in that case. So in such cases, required DMA channels > > > > can be reserved using this config option. For GP devices all > > > > 32 channels can be used currently. > > > > > > > > > > If it can done in better way, please suggest. > > > > > > > > Well how about passing the configuration for the DMA channels > > > > from board-*.c file then? > > > This is certainly a good option if the setting is fixed for > > a particular board type. With this how do we ensure user > > configurability. Lets say on a particular board, two > > users/customers wants to use separate configurations for DMA > > channels because of the needs what mentioned earlier. Then > > again we need some kind of comfit option. > > > Another clean way to achieve this is through 'bootargs'. > > But this might be too much of a design for this requirement. > > > > Hmm, well how about starting with all of them, and allow > > limiting the active DMA number via /sys? I guess we could > > just set some of the DMA channels inactive that way. > > > > Or maybe allow setting indvidual DMA channels inactive > > via /sys? > > This won't be a good option because of few limitations. > - dma library init will configure the entire register set for all the channels. So through /sys disable , you have to mask all of this registers with appropriate mask depending on the no of channels deactivated. This is almost like doing another DMA init. > - Secondly the security driver is active even before the dma library is initialed and hence it won't get the required reservation of channels which is bottleneck. > - If both, dma library and security driver configure the DMA channels then, you end up in a problem because the way OMAP DMA hardware is. Just a brief - "In > contrast to the SDMA.DMA4_CSRi registers, the SDMA.DMA4_IRQSTATUS_Lj registers are updated regardless of the corresponding bits in the SDMA.DMA4_IRQENABLE_Lj registers". For more details, you can refer the DMA section in TRM. > Because of above, this is not seems to be an option. How about set up a cmdline option for omap dma for masking the available channels? Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
