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. >>> >>> It is a bit more complex that this simple patch. How about this one >>> (my original version). As for Jon Master question on McDivitt, not >>> sure what they use for the ACPI table for SPCR. If they used our >>> reference, then this might work for them too. This version would limit >>> to just the existent firmware or until the SPCR table gets changed. >>> >>> >>> tty: 8250: Workaround for APM X-Gene 8250 UART 32-alignment errata >>> >>> APM X-Gene verion 1 and 2 have an 8250 UART with its register >>> aligned to 32-bit. The SPCR always assumes fully compatible >>> 8250. This causes no console with ACPI boot as the console >>> will not match X-Gene UART port due to the lack of mmio32 >>> option. >>> >>> Signed-off-by: Loc Ho <lho@xxxxxxx> >>> --- >>> drivers/acpi/spcr.c | 21 +++++++++++++++++++++ >>> 1 file changed, 21 insertions(+) >>> >>> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c >>> index 3afa8c1..77b45a0 100644 >>> --- a/drivers/acpi/spcr.c >>> +++ b/drivers/acpi/spcr.c >>> @@ -36,6 +36,25 @@ static bool qdf2400_erratum_44_present(struct >>> acpi_table_header *h) >>> return false; >>> } >>> >>> +/* >>> + * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its >>> + * register aligned to 32-bit. This function detects this errata condition. >>> + */ >>> +static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb) >>> +{ >>> + if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE) >>> + return false; >>> + >>> + if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE)) >>> + return false; >>> + >>> + if (!memcmp(tb->header.oem_table_id, "XGENESPC", >>> + ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0) >>> + return true; >>> + >>> + return false; >>> +} >>> + >>> /** >>> * parse_spcr() - parse ACPI SPCR table and add preferred console >>> * >>> @@ -115,6 +134,8 @@ int __init parse_spcr(bool earlycon) >>> >>> if (qdf2400_erratum_44_present(&table->header)) >>> uart = "qdf2400_e44"; >>> + if (xgene_8250_erratum_present(table)) >>> + iotype = "mmio32"; >>> >>> snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype, >>> table->serial_port.address, baud_rate); >>> >> >> I didn't see a follow up email on this. What was the conclusion to >> this patch series? > > I have not received an ack, nack, or gtfo from any of the maintainers > of this file. Per > ./scripts/get_maintainer.pl drivers/acpi/spcr.c > "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx> (supporter:ACPI) > Len Brown <lenb@xxxxxxxxxx> (supporter:ACPI) > linux-acpi@xxxxxxxxxxxxxxx (open list:ACPI) > linux-kernel@xxxxxxxxxxxxxxx (open list) > > Is there someone else I should be directing this patch through? Can you generate a new patch set that includes all the required patches (including mine workaround for X-Gene) and re-post? Then we check with Rafael or Len again. -Loc -- 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
