linux-kernel - [PATCH v1] driver core: Fix handling of fw

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Message-Id: <20200331022832.209618-1-saravanak@google.com>
Date:   Mon, 30 Mar 2020 19:28:32 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        kernel-team@...roid.com, linux-kernel@...r.kernel.org
Subject: [PATCH v1] driver core: Fix handling of fw_devlink=permissive

When commit 8375e74f2bca ("driver core: Add fw_devlink kernel
commandline option") added fw_devlink, it didn't implement "permissive"
mode correctly.

That commit got the device links flags correct to make sure unprobed
suppliers don't block the probing of a consumer. However, if a consumer
is waiting for mandatory suppliers to register, that could still block a
consumer from probing.

This commit fixes that by making sure in permissive mode, all suppliers
to a consumer are treated as a optional suppliers. So, even if a
consumer is waiting for suppliers to register and link itself (using the
DL_FLAG_SYNC_STATE_ONLY flag) to the supplier, the consumer is never
blocked from probing.

Fixes: 8375e74f2bca ("driver core: Add fw_devlink kernel commandline option")
Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
Hi Marek,

If you pull in this patch and then add back in my patch that created the
boot problem for you, can you see if that fixes the boot issue for you?

Thanks,
Saravana

 drivers/base/core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5e3cc1651c78..1be26a7f0866 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2370,6 +2370,11 @@ u32 fw_devlink_get_flags(void)
 	return fw_devlink_flags;
 }

+static bool fw_devlink_is_permissive(void)
+{
+	return fw_devlink_flags == DL_FLAG_SYNC_STATE_ONLY;
+}
+
 /**
  * device_add - add device to device hierarchy.
  * @dev: device.
@@ -2524,7 +2529,7 @@ int device_add(struct device *dev)
 	if (fw_devlink_flags && is_fwnode_dev &&
 	    fwnode_has_op(dev->fwnode, add_links)) {
 		fw_ret = fwnode_call_int_op(dev->fwnode, add_links, dev);
-		if (fw_ret == -ENODEV)
+		if (fw_ret == -ENODEV && !fw_devlink_is_permissive())
 			device_link_wait_for_mandatory_supplier(dev);
 		else if (fw_ret)
 			device_link_wait_for_optional_supplier(dev);
-- 
2.26.0.rc2.310.g2932bb562d-goog