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switchtec: Remove immediate status check after submitting MRPC command

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After submitting a Firmware Download MRPC command, Switchtec firmware will
delay Management EP BAR MemRd TLP responses by more than 10ms.  This is a
firmware limitation.  Delayed MemRd completions are a problem for systems
with a low Completion Timeout (CTO).

The current driver checks the MRPC status immediately after submitting an
MRPC command, which results in a delayed MemRd completion that may cause a
Completion Timeout.

Remove the immediate status check and rely on the check after receiving an
interrupt or timing out.

This is only a software workaround to the READ issue and a proper fix of
this should be done in firmware.

Fixes: 080b47def5 ("MicroSemi Switchtec management interface driver")
Signed-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Wesley Sheng <wesley.sheng@microchip.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
This commit is contained in:
Kelvin Cao 2018-12-10 17:12:20 +08:00 committed by Bjorn Helgaas
parent 651022382c
commit 526180408b
1 changed files with 0 additions and 4 deletions
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4
drivers/pci/switch/switchtec.c
View File

@ -134,10 +134,6 @@ static void mrpc_cmd_submit(struct switchtec_dev *stdev)
stuser->data, stuser->data_len);
iowrite32(stuser->cmd, &stdev->mmio_mrpc->cmd);
stuser->status = ioread32(&stdev->mmio_mrpc->status);
if (stuser->status != SWITCHTEC_MRPC_STATUS_INPROGRESS)
mrpc_complete_cmd(stdev);
schedule_delayed_work(&stdev->mrpc_timeout,
msecs_to_jiffies(500));
}