This driver's only job is to claim and ensure that the necessary clock
for memory operation on a DT-enabled machine remains enabled.
Signed-off-by: Emilio López <emilio@xxxxxxxxxxxxx>
---
Hi,
I am currently facing an issue with the clock setup: a critical but
unclaimed clock gets disabled as a side effect of disabling one of its
children. The clock setup looks something like this:
PLL
|
------------
| |
DDR Others
|
periph
The PLL clock is marked with the CLK_IGNORE_UNUSED flag, so on a normal
boot it remains on, even after the unused clocks cleanup code runs. The
problem occurs when someone enables "periph" and then, later on, disables
it: the framework starts disabling clocks upwards on the tree,
eventually switching the PLL off (and that kills the machine, as the memory
clock is shut down).
There's two possible solutions I can think of:
1) add some extra checks on the framework to not turn off clocks marked
with such a flag on the non-explicit case (ie, when I'm disabling
some other clock)
2) create an actual user of the DDR clock, that way it won't get
disabled simply because it's being used.
I considered 1) and implemented it, but the result was not pretty. This
patch is my take on 2). Please let me know what you think; all feedback
is welcome :)
Cheers,
Emilio
drivers/of/Kconfig | 6 ++++++
drivers/of/Makefile | 1 +
drivers/of/of_memory.c | 30 ++++++++++++++++++++++++++++++
3 files changed, 37 insertions(+)
create mode 100644 drivers/of/of_memory.c
diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index 9d2009a..f6c5e20 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -80,4 +80,10 @@ config OF_RESERVED_MEM
help
Initialization code for DMA reserved memory
+config OF_MEMORY
+ depends on COMMON_CLK
+ def_bool y
+ help
+ Simple memory initialization
+
endmenu # OF
diff --git a/drivers/of/Makefile b/drivers/of/Makefile
index ed9660a..15f0167 100644
--- a/drivers/of/Makefile
+++ b/drivers/of/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_OF_PCI) += of_pci.o
obj-$(CONFIG_OF_PCI_IRQ) += of_pci_irq.o
obj-$(CONFIG_OF_MTD) += of_mtd.o
obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
+obj-$(CONFIG_OF_MEMORY) += of_memory.o
diff --git a/drivers/of/of_memory.c b/drivers/of/of_memory.c
new file mode 100644
index 0000000..a833f7a
--- /dev/null
+++ b/drivers/of/of_memory.c
@@ -0,0 +1,30 @@
+/*
+ * Simple memory driver
+ */
+
+#include <linux/of.h>
+#include <linux/clk.h>
+
+static int __init of_memory_enable(void)
+{
+ struct device_node *np;
+ struct clk *clk;
+
+ np = of_find_node_by_path("/memory");
+ if (!np) {
+ pr_err("no /memory on DT!\n");
+ return 0;
+ }
+
+ clk = of_clk_get(np, 0);
+ if (!IS_ERR(clk)) {
+ clk_prepare_enable(clk);
+ clk_put(clk);
+ }
+
+ of_node_put(np);
+
+ return 0;
+}
+
+device_initcall(of_memory_enable);
--
1.8.4
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