From mboxrd@z Thu Jan 1 00:00:00 1970 From: neilb@suse.de (NeilBrown) Date: Sat, 4 Feb 2012 14:09:23 +1100 Subject: patch "tty: serial: OMAP: ensure FIFO levels are set correctly in non-DMA" added to tty tree In-Reply-To: References: <13274430881471@kroah.org> <20120126042155.GA3185@suse.de> <20120126191604.GA15516@suse.de> <20120203150708.386951d2@notabene.brown> <20120203205401.5ddf241d@notabene.brown> <20120204085940.2de44594@notabene.brown> <20120204110131.7378b8fe@notabene.brown> Message-ID: <20120204140923.063706c8@notabene.brown> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, 3 Feb 2012 19:06:19 -0700 (MST) Paul Walmsley wrote: > Hi Neil > > On Sat, 4 Feb 2012, NeilBrown wrote: > > > Guess what happens if I set autosuspend_delay_ms to 0? > > Massive transmit problems. Driver can hardly get anything out before the > > UART's fclk is cut... > > Just reproduced this on 35xx BeagleBoard. Looks like the UART is indeed > going idle while the TX FIFO has bytes in it. That makes me happy :-) > > Here's a patch that helps. It seems to work down to an > autosuspend_delay_ms of 1 ms. Without it, the best I can get is 8 ms. > > Of course, ideally it should work fine at autosuspend_delay_ms = 0, so > likely there's some other infelicity that we're currently missing. > > Neil, care to give this a test and confirm it on your setup? Yes, that seems to make the output corruption go away. Even with small autosuspend_delay_ms down to 0 it doesn't corrupt output, but as the first input byte is corrupted, I cannot really type with those setting (so I ssh to gain control again). The patch disables the IDLEMODE_SMART setting that happens on runtime suspend/resume so that the IDLEMODE_NO setting stays in force. So it clearly isn't "stopping the clocks" that is the problem - as I first imagined - but rather the SIDLE handshake isn't doing what we think it should do. Thanks, NeilBrown -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 828 bytes Desc: not available URL: