On 17.04.2024 12:50, Jiri Slaby wrote: > On 17. 04. 24, 12:15, Marek Szyprowski wrote: >> On 16.04.2024 12:23, Jiri Slaby wrote: >>> On 15. 04. 24, 23:17, Marek Szyprowski wrote: >>>> On 05.04.2024 08:08, Jiri Slaby (SUSE) wrote: >>>>> This is a preparatory for the serial-to-kfifo switch. kfifo >>>>> understands >>>>> only scatter-gatter approach, so switch to that. >>>>> >>>>> No functional change intended, it's just >>>>> dmaengine_prep_slave_single() >>>>> inline expanded. >>>>> >>>>> And in this case, switch from dma_map_single() to dma_map_sg() too. >>>>> This >>>>> needs struct msm_dma changes. I split the rx and tx parts into an >>>>> union. >>>>> TX is now struct scatterlist, RX remains the old good phys-virt-count >>>>> triple. >>>>> >>>>> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@xxxxxxxxxx> >>>>> Cc: Bjorn Andersson <andersson@xxxxxxxxxx> >>>>> Cc: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx> >>>>> Cc: linux-arm-msm@xxxxxxxxxxxxxxx >>>> >>>> I've just found that this patch broke UART operation on DragonBoard >>>> 410c. I briefly checked and didn't notice anything obviously wrong >>>> here, >>>> but the board stops transmitting any data from its serial port >>>> after the >>>> first message. I will try to analyze this issue a bit more tomorrow. >>> >>> I double checked, but I see no immediate issues in the patch too. So >>> please, if you can analyze this more… >> >> I've spent some time digging into this issue and frankly speaking I >> still have no idea WHY it doesn't work (or I seriously mixed something >> in the scatterlist principles). However I found a workaround to make it >> working. Maybe it will help a bit guessing what happens there. > ... >> @@ -434,7 +436,7 @@ static void msm_start_tx(struct uart_port *port) >> struct msm_dma *dma = &msm_port->tx_dma; >> >> /* Already started in DMA mode */ >> - if (sg_dma_len(&dma->tx_sg)) >> + if (dma->mapped) > > Thanks for looking into this. > > I was hesitant if I should use a flag. I should have, apparently. > > Quick question: > What's value of CONFIG_NEED_SG_DMA_LENGTH in your .config? CONFIG_NEED_SG_DMA_LENGTH=y 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. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
