Re: [PATCH v2 2/3] of/irq: Add new function of_msi_map_rid()

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On 09/23/2015 09:52 AM, Marc Zyngier wrote:
On Tue, 22 Sep 2015 17:00:05 -0700
David Daney <ddaney.cavm@xxxxxxxxx> wrote:

From: David Daney <david.daney@xxxxxxxxxx>

The device tree property "msi-map" specifies how to create the PCI
requester id used in some MSI controllers.  Add a new function
of_msi_map_rid() that finds the msi-map property and applies its
translation to a given requester id.

Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
---
  drivers/of/irq.c       | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++
  include/linux/of_irq.h |  7 ++++
  2 files changed, 93 insertions(+)

diff --git a/drivers/of/irq.c b/drivers/of/irq.c
index 55317fa..3f64d2e 100644
--- a/drivers/of/irq.c
+++ b/drivers/of/irq.c
@@ -598,3 +598,89 @@ void of_msi_configure(struct device *dev, struct device_node *np)
[...]
+	while (!matched && msi_map_len >= 4 * sizeof(__be32)) {
+		rid_base = be32_to_cpup(msi_map + 0);
+		phandle = be32_to_cpup(msi_map + 1);
+		msi_base = be32_to_cpup(msi_map + 2);
+		rid_len = be32_to_cpup(msi_map + 3);

Rob did suggest to use of_property_read_u32_index() instead of these
be32_to_cpup(). Not sure if that'd be a major improvement though.


I did think about that, but the micro-optimizer in me didn't feel comfortable with the overhead of rerunning of_find_property() for each value. I decided to run of_find_property() once, and then iterate through the individual values within the property.

If there are strong objections to doing it this way, we can change it.

David Daney
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