Messages in this thread | | | Subject | Re: [PATCH] serial: 8250_lpss: Unconditionally set PCI master for Quark | From | Andy Shevchenko <> | Date | Tue, 10 Jan 2017 14:06:22 +0200 |
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On Mon, 2017-01-09 at 18:00 +0100, Jan Kiszka wrote: > On 2017-01-05 22:54, Andy Shevchenko wrote: > > On Wed, Jan 4, 2017 at 10:48 PM, Jan Kiszka <jan.kiszka@siemens.com> > > wrote: > > > MSI needs it as well. > > > > > > Should have no practical impact, though, as DMA is always > > > available on > > > the Quark. But given the few users of pci_alloc_irq_vectors so > > > far, this > > > incorrect pattern may spread otherwise. > > > > > > > One question below. > > > > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com> > > > > > Fixes: 3f3a46951e02 ("serial: 8250_lpss: set PCI master only for > > > private DMA") > > > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> > > > --- > > > drivers/tty/serial/8250/8250_lpss.c | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/tty/serial/8250/8250_lpss.c > > > b/drivers/tty/serial/8250/8250_lpss.c > > > index f09f68a..9315197 100644 > > > --- a/drivers/tty/serial/8250/8250_lpss.c > > > +++ b/drivers/tty/serial/8250/8250_lpss.c > > > @@ -183,7 +183,6 @@ static void qrk_serial_setup_dma(struct > > > lpss8250 *lpss, struct uart_port *port) > > > if (ret) > > > return; > > > > > > - pci_set_master(pdev); > > > pci_try_set_mwi(pdev); > > > > Does it make sense to move MWI there as well? > > TBH, I didn't come across the need to enable this bit so far, > specifically not for doing MSI transactions. Is MWI used at all for > MSI > (spec says that MSI is "using a PCI DWORD memory write transaction")?
No, it can't. PCIe has no MWI feature at all, but you may have MSI there.
> That question is better answered by someone more familiar with such > PCI > details.
In most (modern) cases trying MWI is no-op.
So, I think you may send v2 of this with my tag without any changes in the code. Thanks!
-- Andy Shevchenko <andriy.shevchenko@linux.intel.com> Intel Finland Oy
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