On Wed, May 11, 2016 at 06:41:26PM -0700, Stephen Boyd wrote: > On 05/10, Abhishek Sahu wrote: > > From: Charanya <charanya@xxxxxxxxxxxxxx> > > Was it intentional to only have one name here? > > > > > The Data loss was happening with current QCOM MSM serial driver during > > large file transfer due to simultaneous enabling of both UART and > > DMA interrupt. When UART operates in DMA mode, RXLEV (Rx FIFO over > > watermark) or RXSTALE (stale interrupts) should not be enabled, > > since these conditions will be handled by DMA controller itself. > > If these interrupts are enabled then normal UART ISR will read some > > bytes of data from Rx Buffer and DMA controller will not receive > > these bytes of data, which will cause data loss. > > > > Now this patch removed the code for enabling of RXLEV and RXSTALE > > interrupt in DMA Rx completion routine. > > I'm lost, we keep both these irqs masked (well only if uartdm > version is 1.4 or greater) pretty much the entire time we're > using DMA for RX. msm_start_rx_dma() will mask them and then when > the callback completes we'll unmask them (the part that's deleted > in this patch), but then we'll go back and remask them almost > immediately because we call msm_start_rx_dma() from the dma > completion handler. > > Can you clearly describe how this is actually fixing any > problems? What's the sequence of events that happens to cause > corruption? > > This does raise the question though why we ever mask/unmask these > interrupts if we're always going to keep them masked while doing > DMA RX. Presumably if we can use DMA to RX, we can always use it > and set things up properly at startup time instead of later on. Thats probably the right thing to do. We shouldn't be masking/unmasking the unused IRQs to begin with. -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
