After submit a Firmware Download (Download sub-command) MRPC command, Switchtec firmware refuses to response any management EP's BAR access until current flash programming finished. During this time, a READ TLP to the gas area in the BAR of the management EP will complete with significant delay like more than 10ms. It's a Switchtec firmware limitation that READ requests cannot get prompt service during firmware download. The delayed completion of READ TLP would be a problem on some system which is sensitive to READ timeout. Current driver check status immediately after submit a MRPC command, which triggers READ TLP to the gas area in the BAR of the management EP. Also, other processes or functions, like NTB, would also trigger READ TLP by accessing the GAS. To avoid this, the immediate check of status is removed in this patch, and driver delays the status check to the occurrence of MSIx or MRPC timeout. In the meantime, user must not initiate any gas access during a firmware download. Also, any process that issues MRPC command will be affected by the delay in this patch. However, this is only a software workaround to the READ issue in firmware download. A complete fix of this should happen in firmware. Note: For NTB function, the memory window access is handled by Switchtec hardware. So it's not affected by this firmware limitation. But the other GAS access which is handled by Switchtec firmware is are affected by this firmware limitation. Signed-off-by: Kelvin Cao <Kelvin.Cao@xxxxxxxxxxxxx> Signed-off-by: Wesley Sheng <Wesley.sheng@xxxxxxxxxxxxx> --- drivers/pci/switch/switchtec.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/drivers/pci/switch/switchtec.c b/drivers/pci/switch/switchtec.c index 4591f15..b759228 100644 --- a/drivers/pci/switch/switchtec.c +++ b/drivers/pci/switch/switchtec.c @@ -142,10 +142,6 @@ 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)); } -- 2.7.4
