From mboxrd@z Thu Jan 1 00:00:00 1970 From: lee.jones@linaro.org (Lee Jones) Date: Fri, 12 Apr 2013 17:13:25 +0100 Subject: [PATCH 3/8] dmaengine: ste_dma40: Actually write the runtime configuration to registers In-Reply-To: References: <1365532783-27425-1-git-send-email-lee.jones@linaro.org> <1365532783-27425-3-git-send-email-lee.jones@linaro.org> Message-ID: <20130412161325.GB18459@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 12 Apr 2013, Rabin Vincent wrote: > 2013/4/9 Lee Jones : > > 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(). Ah, I see. I'll move it all back and investigate my bug further then. Thanks for taking the time to write such a well written review. -- Lee Jones Linaro ST-Ericsson Landing Team Lead Linaro.org ? Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog