On 19.04.2024 09:53, Jiri Slaby wrote: > On 19. 04. 24, 9:43, Jiri Slaby wrote: >> On 17. 04. 24, 14:45, Marek Szyprowski wrote: >>> I alse tried to change the "if (dma->mapped)" check in >>> msm_start_tx() to: >>> >>> 1. if (dma->tx_sg.length) >>> >>> 2. if (dma->tx_sg.page_link & ~SG_PAGE_LINK_MASK) >>> >>> but none of the above worked what is really strange and >>> incomprehensible >>> for me. >>> >> >> Aaaah, nevermind, what about this? >> >> Two bugs: >> 1) dma_map_sg() returns the number of mapped entries. Not zero! >> 2) And I forgot to zero tx_sg in case of error. >> >> --- a/drivers/tty/serial/msm_serial.c >> +++ b/drivers/tty/serial/msm_serial.c >> @@ -506,8 +506,8 @@ static int msm_handle_tx_dma(struct msm_port >> *msm_port, unsigned int count) >> kfifo_dma_out_prepare(&tport->xmit_fifo, &dma->tx_sg, 1, >> count); >> >> ret = dma_map_sg(port->dev, &dma->tx_sg, 1, dma->dir); >> - if (ret) >> - return ret; >> + if (!ret) > > Still wrong, ret = -EIO missing in here. "if (ret <= 0)" seems to be better here. Indeed this fixed the issue. I checked the code many times, but I missed this dma_map_sg() return value issue. Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > >> + goto zero_out; >> >> dma->desc = dmaengine_prep_slave_sg(dma->chan, &dma->tx_sg, 1, >> DMA_MEM_TO_DEV, >> @@ -548,6 +548,7 @@ static int msm_handle_tx_dma(struct msm_port >> *msm_port, unsigned int count) >> return 0; >> unmap: >> dma_unmap_sg(port->dev, &dma->tx_sg, 1, dma->dir); >> +zero_out: >> sg_init_table(&dma->tx_sg, 1); >> return ret; >> } >> >> >> thanks, > Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
