Re: [PATCH 3/3] CXL: Add reset to sysfs

On 01/15/2015 12:42 AM, Ian Munsie wrote:

Excerpts from Ryan Grimm's message of 2015-01-15 13:56:41 +1100:

quoted

This allows an image to be downloaded to the flash without rebooting the
machine.  The driver perform a PERST, which results in FPGA image downloaded to
flash and the CAPP unit enters recovery.  CAPP recovery triggers an HMI, which
is handled by EEH in Linux.  EEH removes the driver, calls into Sapphire to
reinitialize the PHB, and then loads the driver.

reset_image_select must be set to "user" and reset_load_image set to 1.  The
driver writes "user" to the vsec if a user image was loaded.  It writes 1 to
reset_load_image on initialization by default.  Other values could be used by
hand for debugging purposes.

That last paragraph will need to be updated if we merge those two sysfs
files into one. Might as well mention an example of why someone might do
a reset with no image selected for reload, e.g. the PSL trace arrays are
preserved, which can be read out through debugfs after the card comes
back up.

OK, fixed that up a bit.  Let me know if the commit logs and 
documentations make sense.  There's a bit of overlap and hopefully it's 
clear now.

quoted

+What:           /sys/class/cxl/<card>/reset
+Date:           October 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    write only
+                Writing 1 here will issue a PERST to card.

"..., which may cause the card to reload the FPGA image depending on the
settings of reset_image_select."

Sure, can be explicit about that.

quoted

+    if ((rc = pci_set_pcie_reset_state(dev, pcie_warm_reset))) {

Can you add a comment here to explain why we first do a warm reset?

quoted

+        dev_err(&dev->dev, "cxl: pcie_warm_reset failed\n");
+        return rc;
+    }
+
+    /* Do mmio read to trigger EEH.  Retry for a few seconds. */

This seems a little unusual - can you expand this comment a little to
explain *why* we are using this method to trigger an EEH and reset the
card?

Added better commenting to both above.

quoted

+    i = 0;
+        while ((val = mmio_read32be(adapter->p1_mmio) != 0xffffffff) &&
+        (i < 5)) {
+                msleep(500);
+        i++;
+        }
+
+        if (val != 0xffffffff)
+                dev_err(&dev->dev, "cxl: PERST failed to trigger EEH\n");
+
+    return rc;

Some of the indentation here is a bit funky - some lines are using tabs,
others are using spaces.

Ouch, yep, fixed.

quoted

@@ -806,8 +837,8 @@ static int cxl_read_vsec(struct cxl *adapter, struct pci_dev *dev)
      CXL_READ_VSEC_BASE_IMAGE(dev, vsec, &adapter->base_image);
      CXL_READ_VSEC_IMAGE_STATE(dev, vsec, &image_state);
      adapter->user_image_loaded = !!(image_state & CXL_VSEC_USER_IMAGE_LOADED);
-    adapter->perst_loads_image = !!(image_state & CXL_VSEC_PERST_LOADS_IMAGE);
-    adapter->perst_select_user = !!(image_state & CXL_VSEC_PERST_SELECT_USER);
+    adapter->perst_loads_image = true;
+    adapter->perst_select_user = !!(image_state & CXL_VSEC_USER_IMAGE_LOADED);

...

quoted

+    if ((rc = cxl_update_image_control(adapter)))
+        goto err2;

Thanks - that seems like a better default than what we had before,
should make things more stable :)

Yeah for sure.

-Ryan

Cheers,
-Ian