Messages in this thread | | | Subject | Re: [PATCH v2 1/2] dt-bindings: Document the STM32 QSPI bindings | From | Ludovic BARRE <> | Date | Wed, 5 Apr 2017 18:00:39 +0200 |
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On 04/04/2017 02:20 PM, Rob Herring wrote: > On Tue, Apr 4, 2017 at 2:28 AM, Ludovic BARRE <ludovic.barre@st.com> 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@st.com> >>>> >>>> This patch adds documentation of device tree bindings for the STM32 >>>> QSPI controller. >>>> >>>> Signed-off-by: Ludovic Barre <ludovic.barre@st.com> >>>> --- >>>> .../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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