Messages in this thread | | | Date | Mon, 10 Aug 2015 14:19:37 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH 1/3] tty: serial: 8250_omap: do not use RX DMA if pause is not supported |
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On 08/10/2015 01:54 PM, Peter Ujfalusi wrote: >> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c >> index 0340ee6ba970..07a11e0935e4 100644 >> --- a/drivers/tty/serial/8250/8250_omap.c >> @@ -769,7 +771,9 @@ static void omap_8250_rx_dma_flush(struct uart_8250_port *p) >> return; >> } >> >> - dmaengine_pause(dma->rxchan); >> + ret = dmaengine_pause(dma->rxchan); >> + if (WARN_ON_ONCE(ret)) >> + priv->rx_dma_broken = true; > > I don't think this is good thing for the stable _and_ for the mainline at the > same time: > in stable the rx DMA should not be allowed since the stable kernels does not > allow pause/resume with omap-dma, so there the rx DMA should be just disabled > for UART. This change will cause regression since it introduce a WARN_ON_ONCE, > which will be printed if the user tries to use non working feature.
Okay. We do have pause support in mainline for edma since v4.2-rc1. This driver can use edma or sdma depending on the configuration. But it is not yet released. So you suggest remove RX-DMA support completely from the 8250-omap, mark it stable, and revert that patch once we have it fixed in sdma?
> In mainline you will eventually going to have pause/resume support so this > patch will make no sense there.
The way this works is that it has to be fixed upstream before it can be backported stable. Also Russell made clear (for a good reason) that the RX problem has to be fixed upstream before he thinks about acking the SDMA patch. So if you prefer to instead remove RX-DMA until it is fixed, I am all yours.
Sebastian
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