Hi Ben, I love your patch! Perhaps something to improve: [auto build test WARNING on sof-driver-fuweitax/master] [also build test WARNING on v4.19-rc7 next-20181012] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Ben-Dooks/dma-tegra-avoid-overflow-of-byte-tracking/20181013-023951 base: https://github.com/fuweitax/linux master config: arm-allmodconfig (attached as .config) compiler: arm-linux-gnueabi-gcc (Debian 7.2.0-11) 7.2.0 reproduce: wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # save the attached .config to linux build tree GCC_VERSION=7.2.0 make.cross ARCH=arm Note: it may well be a FALSE warning. FWIW you are at least aware of it now. http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings All warnings (new ones prefixed by >>): In file included from include/linux/printk.h:332:0, from include/linux/kernel.h:14, from include/linux/clk.h:16, from drivers//dma/tegra20-apb-dma.c:20: drivers//dma/tegra20-apb-dma.c: In function 'tegra_dma_tx_status': include/linux/dynamic_debug.h:135:3: warning: 'done' may be used uninitialized in this function [-Wmaybe-uninitialized] __dynamic_dev_dbg(&descriptor, dev, fmt, \ ^~~~~~~~~~~~~~~~~ drivers//dma/tegra20-apb-dma.c:816:6: note: 'done' was declared here int done; ^~~~ In file included from include/linux/printk.h:332:0, from include/linux/kernel.h:14, from include/linux/clk.h:16, from drivers//dma/tegra20-apb-dma.c:20: include/linux/dynamic_debug.h:135:3: warning: 'wcount' may be used uninitialized in this function [-Wmaybe-uninitialized] __dynamic_dev_dbg(&descriptor, dev, fmt, \ ^~~~~~~~~~~~~~~~~ drivers//dma/tegra20-apb-dma.c:811:16: note: 'wcount' was declared here unsigned long wcount; ^~~~~~ >> drivers//dma/tegra20-apb-dma.c:843:30: warning: 'sg_req' may be used uninitialized in this function [-Wmaybe-uninitialized] result = residual - sg_req->req_len; ~~~~~~^~~~~~~~~ drivers//dma/tegra20-apb-dma.c:894:27: note: 'sg_req' was declared here struct tegra_dma_sg_req *sg_req; ^~~~~~ vim +/sg_req +843 drivers//dma/tegra20-apb-dma.c 804 805 static unsigned int tegra_dma_update_residual(struct tegra_dma_channel *tdc, 806 struct tegra_dma_sg_req *sg_req, 807 struct tegra_dma_desc *dma_desc, 808 unsigned int residual) 809 { 810 unsigned long status = 0x0; 811 unsigned long wcount; 812 unsigned long ahbptr; 813 unsigned long tmp = 0x0; 814 unsigned int result; 815 int retries = TEGRA_APBDMA_BURST_COMPLETE_TIME * 10; 816 int done; 817 818 /* if we're not the current request, then don't alter the residual */ 819 if (sg_req != list_first_entry(&tdc->pending_sg_req, 820 struct tegra_dma_sg_req, node)) { 821 result = residual; 822 ahbptr = 0xffffffff; 823 goto done; 824 } 825 826 /* loop until we have a reliable result for residual */ 827 do { 828 ahbptr = tdc_read(tdc, TEGRA_APBDMA_CHAN_AHBPTR); 829 status = tdc_read(tdc, TEGRA_APBDMA_CHAN_STATUS); 830 tmp = tdc_read(tdc, 0x08); /* total count for debug */ 831 832 /* check status, if channel isn't busy then skip */ 833 if (!(status & TEGRA_APBDMA_STATUS_BUSY)) { 834 result = residual; 835 break; 836 } 837 838 /* if we've got an interrupt pending on the channel, don't 839 * try and deal with the residue as the hardware has likely 840 * moved on to the next buffer. return all data moved. 841 */ 842 if (status & TEGRA_APBDMA_STATUS_ISE_EOC) { > 843 result = residual - sg_req->req_len; 844 break; 845 } 846 847 if (tdc->tdma->chip_data->support_separate_wcount_reg) 848 wcount = tdc_read(tdc, TEGRA_APBDMA_CHAN_WORD_TRANSFER); 849 else 850 wcount = status; 851 852 /* If the request is at the full point, then there is a 853 * chance that we have read the status register in the 854 * middle of the hardware reloading the next buffer. 855 * 856 * The sequence seems to be at the end of the buffer, to 857 * load the new word count before raising the EOC flag (or 858 * changing the ping-pong flag which could have also been 859 * used to determine a new buffer). This means there is a 860 * small window where we cannot determine zero-done for the 861 * current buffer, or moved to next buffer. 862 * 863 * If done shows 0, then retry the load, as it may hit the 864 * above hardware race. We will either get a new value which 865 * is from the first buffer, or we get an EOC (new buffer) 866 * or both a new value and an EOC... 867 */ 868 done = get_current_xferred_count(tdc, sg_req, wcount); 869 if (done != 0) { 870 result = residual - done; 871 break; 872 } 873 874 ndelay(100); 875 } while (--retries > 0); 876 877 if (retries <= 0) { 878 dev_err(tdc2dev(tdc), "timeout waiting for dma load\n"); 879 result = residual; 880 } 881 --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
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