Commit 52618040 authored Dec 10, 2018 by Kelvin Cao Committed by Bjorn Helgaas Dec 12, 2018

switchtec: Remove immediate status check after submitting MRPC command



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: 080b47de ("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>

parent 65102238

drivers/pci/switch/switchtec.c

+0 −4

Original line number	Diff line number	Diff line
		@@ -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));
		}

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