> -----Original Message----- > From: Wood Scott-B07421 > Sent: Thursday, March 14, 2013 4:24 AM > To: Michael Ellerman > Cc: Jia Hongtao-B38951; linuxppc-dev@lists.ozlabs.org; > ga...@kernel.crashing.org; Wood Scott-B07421 > Subject: Re: [PATCH] powerpc/85xx: workaround for chips with MSI hardware > errata > > On 03/13/2013 12:04:03 AM, Michael Ellerman wrote: > > On Tue, Mar 12, 2013 at 03:48:02PM +0800, Jia Hongtao wrote: > > > The MPIC chip with version 2.0 has a MSI errata (errata PIC1 of > > mpc8544), > > > It causes that neither MSI nor MSI-X can work fine. This is a > > workaround > > > to allow MSI-X to function properly. > > > > You say "neither MSI nor MSI-X can work fine", which I take to mean > > "both MSI and MSI-X do not work". > > > > But then you say this is a workaround to allow MSI-X to work. > > > > So what I think you mean is, the erratum prevents both MSI and MSI-X > > from working. This is a workaround that allows MSI-X to work, and in > > addition the patch prevents MSI from being used on chips with the > > erratum - because there is no workaround for MSI. > > There actually is a workaround for MSI, but it's more complicated and not > implemented by this patch. > > We could also possibly get away with allowing exactly one MSI > (byteswapping doesn't matter if the value is zero) -- not sure how hard > that would be.
For now we have no plan to support MSI workaround. Also MSI workaround deserve a new patch :) I will sent V2 of this patch soon. -Hongtao. > > > > + list_for_each_entry(msi, &msi_head, list) > > > + if (msi->feature & MSI_HW_ERRATA_ENDIAN) > > > + return -EINVAL; > > > > I take it you're happy preventing MSI for all devices even if only a > > single chip in the machine has the erratum? In practice you probably > > have all or none with the erratum right? > > Yes, it's all integrated onto one chip (the SoC itself). In fact there > should only be one MSI block on these chips. > > -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
