On Mon, May 08, 2017 at 01:51:20PM -0700, Loc Ho wrote: > Hi Jon, > > On Mon, May 8, 2017 at 1:34 PM, Jon Mason <jon.mason@xxxxxxxxxxxx> wrote: > > On Mon, May 8, 2017 at 3:57 PM, Loc Ho <lho@xxxxxxx> wrote: > >> Hi Jon, > >> > >>>> > >>>>>> The current SPCR code does not check the access width of the mmio, and > >>>>>> uses a default of 8bit register accesses. This prevents devices that > >>>>>> only do 16 or 32bit register accesses from working. By simply checking > >>>>>> this field and setting the mmio string appropriately, this issue can be > >>>>>> corrected. To prevent any legacy issues, the code will default to 8bit > >>>>>> accesses if the value is anything but 16 or 32. > >>>>> > >>>>> Thanks for this. Just as an FYI I've a running discussion with Microsoft > >>>>> about defining additional UART subtypes in the DBG2 for special case > >>>>> UARTs. Specifically, I want to address AppliedMicro's special 8250 dw IP > >>>>> that also has a non-standard clock. At this time, there is general > >>>>> agreement to use the access width for some cases rather than defining > >>>>> yet more subtypes - so your patch is good. > >>>>> > >>>>> Loc/Applied: please track this thread, incorporate feedback, and also > >>>>> track the other general recent discussions of 8250 dw from this week. > >>>> > >>>> Thanks for forward me this patch. This patch does not work with X-Gene > >>>> v1 and v2 SoC's. As BIOS SPCR encodes these info as: > >>>> > >>>> Bit Width: 32 > >>>> Bit Offset: 0 > >>>> Encoded Access Width: 01 (Byte Access) > >>>> > >>>> With this patch, it would use the "mmio" instead the "mmio32" as with > >>>> this patch - https://patchwork.kernel.org/patch/9460959 > >>> > >>> I think this is why we need the DBG2 subtype for Applied X-Gene1. I'm > >>> hoping the update to the SPCR/DBG2 spec is done soon. > >> > >> We can't rely on the BIOS change to support this new subtype as we > >> have system that is already in production deployment. When these > >> system upgrade to new version of the OS (stock, RHELSA, or whatever), > >> they will break. We need the patch from > >> https://patchwork.kernel.org/patch/9460959/ rolled upstream. > > > > There is no reason why the patch you reference cannot co-exist with > > the one I am submitting here. In this case, my patch would set it to > > mmio, then the patch you link above would reset it to mmio32. > > Personally, I would recommend a big, fat comment on why this extra > > step is necessary, but it should work as desired. Alternatively, we > > could add some kind of quirk library (similar to > > qdf2400_erratum_44_present) where the OEM/OEM Table ID is referenced > > and workaround applied. Thoughts? > > That's was my first version but after seeing both versions, I think > they are better solution as it works for more SoC's than just our. As > you had suggested, we should apply your patch and > https://patchwork.kernel.org/patch/9460959. The third patch - > https://patchwork.kernel.org/patch/9462183/ - conflicts with your. > > Summary: > 1. Applied your - https://lkml.org/lkml/2017/5/4/450 > 2. Applied this one - https://patchwork.kernel.org/patch/9460959/ > > -Loc What if we simply applied the following (100% untested) patch to add the quirk framework I was suggesting? It can be applied on top of the patch I submitted previously. diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c index 63b690d142f1..c87569b345e3 100644 --- a/drivers/acpi/spcr.c +++ b/drivers/acpi/spcr.c @@ -36,6 +36,14 @@ static bool qdf2400_erratum_44_present(struct acpi_table_header *h) return false; } +static void spcr_quirks(struct acpi_table_spcr *table, char **iotype) +{ + struct acpi_table_header *h = &table->header; + + if (!memcmp(h->oem_table_id, "XGENESPC", ACPI_OEM_TABLE_ID_SIZE)) + *iotype = "mmio32"; +} + /** * parse_spcr() - parse ACPI SPCR table and add preferred console * @@ -88,6 +96,9 @@ int __init parse_spcr(bool earlycon) iotype = "mmio32"; break; } + + /* Fixup any non-standard compliant devices */ + spcr_quirks(table, &iotype); } else iotype = "io"; -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
