On 04/04/2017 02:20 PM, Rob Herring wrote:
On Tue, Apr 4, 2017 at 2:28 AM, Ludovic BARRE <ludovic.barre@xxxxxx> wrote:
Hi Rob
thanks for review
my comments below
br
Ludo
On 04/03/2017 06:57 PM, Rob Herring wrote:
On Fri, Mar 31, 2017 at 07:02:03PM +0200, Ludovic Barre wrote:
From: Ludovic Barre <ludovic.barre@xxxxxx>
This patch adds documentation of device tree bindings for the STM32
QSPI controller.
Signed-off-by: Ludovic Barre <ludovic.barre@xxxxxx>
---
.../devicetree/bindings/mtd/stm32-quadspi.txt | 45
++++++++++++++++++++++
1 file changed, 45 insertions(+)
create mode 100644
Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
diff --git a/Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
b/Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
new file mode 100644
index 0000000..95a8ebd
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/stm32-quadspi.txt
@@ -0,0 +1,45 @@
+* STMicroelectronics Quad Serial Peripheral Interface(QuadSPI)
+
+Required properties:
+- compatible: should be "st,stm32f469-qspi"
+- reg: contains the register location and length.
+ (optional) the memory mapping address and length
Why optional? Either the h/w has it or doesn't. If some chips don't,
they should have a different compatible string.
in fact, the stm32 qspi controller can operate in any of the following
modes:
-indirect mode: all the operations are performed using the qspi registers
with read/write.
-read memory-mapped mode: the external Flash memory is mapped to the
microcontroller address space and is seen by the system as if it was
an internal memory (use memcpy_fromio). this mode improve read throughput
if qspi_mm is defined the qspi controller use read memory-mapped mode
else the controller transfers in indirect mode.
You should always have the memory region defined because that's what
the h/w has. If you want another property to select the mode, then
perhaps that's fine. But why? Can't the OS figure out which to use?
Why would you ever not use memory mapped mode unless the driver
doesn't yet support it?
ok, I always map the memory region (qspi_mm is now required).
if the nor-flash is more bigger than "qspi memory region", I force to use
the indirect mode.
Rob
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