Re: [PATCHv3 2/7] EDAC, altera: Add panic flag check to A10 IRQ

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Hi Boris,

On 06/17/2016 11:51 AM, Borislav Petkov wrote:
On Mon, Jun 13, 2016 at 04:19:07PM -0500, tthayer@xxxxxxxxxxxxxxxxxxxxx wrote:
From: Thor Thayer <tthayer@xxxxxxxxxxxxxxxxxxxxx>

In preparation for additional memory module ECCs, the
IRQ function will check a panic flag before doing a
kernel panic on double bit errors. ECCs on buffers
will not cause a kernel panic on DBERRs.

Signed-off-by: Thor Thayer <tthayer@xxxxxxxxxxxxxxxxxxxxx>
---
v2  New patch. Add panic flag to IRQ function.
v3  No change
---
  drivers/edac/altera_edac.c |    4 +++-
  drivers/edac/altera_edac.h |    1 +
  2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/edac/altera_edac.c b/drivers/edac/altera_edac.c
index 926bcaf..a9d8fa7 100644
--- a/drivers/edac/altera_edac.c
+++ b/drivers/edac/altera_edac.c
@@ -897,7 +897,8 @@ static irqreturn_t altr_edac_a10_ecc_irq(int irq, void *dev_id)
  		writel(ALTR_A10_ECC_DERRPENA,
  		       base + ALTR_A10_ECC_INTSTAT_OFST);
  		edac_device_handle_ue(dci->edac_dev, 0, 0, dci->edac_dev_name);
-		panic("\nEDAC:ECC_DEVICE[Uncorrectable errors]\n");
+		if (dci->data->panic)
+			panic("\nEDAC:ECC_DEVICE[Uncorrectable errors]\n");

  		return IRQ_HANDLED;
  	}
@@ -936,6 +937,7 @@ const struct edac_device_prv_data a10_ocramecc_data = {
  	.set_err_ofst = ALTR_A10_ECC_INTTEST_OFST,
  	.ecc_irq_handler = altr_edac_a10_ecc_irq,
  	.inject_fops = &altr_edac_a10_device_inject_fops,
+	.panic = true,

So I could use a bit more detailed explanation here why OCRAM must panic
and the others don't. Consider me an external guy who doesn't know the
hardware and is looking at the driver and is wondering why this IP must
panic on double-bit errors and the others don't.

:-)

Thanks.

That is a good question. We have 2 important uses for OCRAM 1) to hold our power-down/sleep and resume functions and 2) to hold our FPGA contents during sleep. If either of these is corrupted, it is better to panic than to load something that would cause incorrect.

In the cases of the FIFOs such as Ethernet and USB, the plan is to add code to drop the packet so that we'll get a re-transmission. In that case, it is sort of recoverable.

Thor

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