On Mon, 15 Apr 2013, Rabin Vincent wrote: > 2013/4/15 Lee Jones <lee.jo...@linaro.org>: > > On Fri, 12 Apr 2013, Rabin Vincent wrote: > >> 2013/4/9 Lee Jones <lee.jo...@linaro.org>: > >> > Someone has spent a fair amount of effort writing a runtime configuration > >> > changing algorithm for DMA clients. However, the config appears to never > >> > actually make it to hardware. In order for the configuration to take hold > >> > we need to issue a d40_config_write(), as this is the routine which > >> > writes > >> > it into the hardware's registers. > >> > >> No, it's not. This function is only for initial configuration which > >> should only be written when the channel is allocated. In fact, by > >> calling it here in runtime_config, you are introducing a serious bug: > >> other logical channels on the same physical channel will stop because of > >> the SSLNK/SDLNK of the physical channel being zeroed. > >> > >> The runtime config already makes it the hardware in the existing code, > >> via d40_*_cfg(). > > > > Sorry Rabin, but the only place I can see the config being written is > > in d40_config_write(). > > > > Can you paste the line of code in d40_*_cfg() which actually writes > > the config to hardware please? I don't see it. > > It's not that simple. There are some pointers passed to d40_*_cfg() and > that function writes the configuration to the variables those pointers > point to (d40c->log_def.lcsp1, d40c->src_def_cfg, etc.). Please read > the code to see how those variables end up being used later when the > LLIs are prepared for the HW.
I have read the code, which is why I know that the config only gets written in d40_config_write(). :) So the configuration which gets set in the runtime_config routine doesn't ever make it to hardware - hence this patch. Unless I'm missing something? -- Lee Jones Linaro ST-Ericsson Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/