On Thu, Apr 26, 2018 at 03:42:01PM +0200, Andrew Jones wrote: > On Thu, Apr 26, 2018 at 01:11:41PM +0100, Peter Maydell wrote: > > On 26 April 2018 at 11:54, Dave Martin <Dave.Martin@xxxxxxx> wrote: > > > This is an update to a previous RFC v3 [1], to fix a problem observed by > > > the qemu community that causes serial input to hang when booting a > > > simulated system with data already queued in the UART FIFO [2]. > > > > > > RFC v3 did not solve the problem by itself, due to the problem being > > > triggered again in pl011_enable_interrupts() after working around it > > > in pl011_hwinit(). See the updated commit message in the patch for > > > details. > > > > > > This patch is intended to supersede the previous RFCs, so please test > > > _without_ RFC v2 (or 3) applied. > > > > > > If you can, please: > > > > > > a) Check that you can still reproduce the bug on mainline without this > > > patch. > > > > > > b) Check whether this patch fixes the problem. > > > > Adding back to the CC list the people who might be able to do > > this testing... > > Link to v4 patch: > > https://patchwork.kernel.org/patch/10365551/ > > > > Tested-by: Andrew Jones <drjones@xxxxxxxxxx> > > And > > Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx> > > as this patch is consistent with what I expected was needed back > when I reported the issue[*]. I was just too dense to realize > that we didn't need to "reset" the FIFO, but rather just drain it. Thanks for the testing and review! There seem to be a few ways to solve this, and it's hard to know which ne is best. This at least looks simple now. Possibly there is a way to reset the FIFO on a real PL011, but I ignored the possibility since there is definitely no way to do that on e.g., SBSA UART. Draining the FIFO by hand ought to work on all variants IIUC. Cheers ---Dave > > Thanks, > drew > > [*] https://lkml.org/lkml/2016/8/1/247 > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- 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
