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    SubjectRe: [PATCH v7 3/5] mtd: Add support for HyperBus memory devices
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    Hello!

    On 06/20/2019 08:22 PM, Vignesh Raghavendra wrote:

    > Cypress' HyperBus is Low Signal Count, High Performance Double Data Rate
    > Bus interface between a host system master and one or more slave
    > interfaces. HyperBus is used to connect microprocessor, microcontroller,
    > or ASIC devices with random access NOR flash memory (called HyperFlash)
    > or self refresh DRAM (called HyperRAM).
    >
    > Its a 8-bit data bus (DQ[7:0]) with Read-Write Data Strobe (RWDS)
    > signal and either Single-ended clock(3.0V parts) or Differential clock
    > (1.8V parts). It uses ChipSelect lines to select b/w multiple slaves.
    > At bus level, it follows a separate protocol described in HyperBus
    > specification[1].
    >
    > HyperFlash follows CFI AMD/Fujitsu Extended Command Set (0x0002) similar
    > to that of existing parallel NORs. Since HyperBus is x8 DDR bus,
    > its equivalent to x16 parallel NOR flash wrt bits per clock cycle. But
    > HyperBus operates at >166MHz frequencies.

    s/wrt/WRT/.

    > HyperRAM provides direct random read/write access to flash memory
    > array.
    >
    > But, HyperBus memory controllers seem to abstract implementation details
    > and expose a simple MMIO interface to access connected flash.
    >
    > Add support for registering HyperFlash devices with MTD framework. MTD
    > maps framework along with CFI chip support framework are used to support
    > communicating with flash.
    >
    > Framework is modelled along the lines of spi-nor framework. HyperBus
    > memory controller (HBMC) drivers calls hyperbus_register_device() to
    > register a single HyperFlash device. HyperFlash core parses MMIO access
    > information from DT, sets up the map_info struct, probes CFI flash and
    > registers it with MTD framework.
    >
    > Some HBMC masters need calibration/training sequence[3] to be carried
    > out, in order for DLL inside the controller to lock, by reading a known
    > string/pattern. This is done by repeatedly reading CFI Query
    > Identification String. Calibration needs to be done before trying to detect
    > flash as part of CFI flash probe.
    >
    > HyperRAM is not supported at the moment.
    >
    > HyperBus specification can be found at[1]
    > HyperFlash datasheet can be found at[2]
    >
    > [1] https://www.cypress.com/file/213356/download
    > [2] https://www.cypress.com/file/213346/download
    > [3] http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf
    > Table 12-5741. HyperFlash Access Sequence
    >
    > Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
    [...]
    > diff --git a/include/linux/mtd/hyperbus.h b/include/linux/mtd/hyperbus.h
    > new file mode 100644
    > index 000000000000..ead969aad35b
    > --- /dev/null
    > +++ b/include/linux/mtd/hyperbus.h
    > @@ -0,0 +1,86 @@
    [...]
    > +/**
    > + * struct hyperbus_ops - struct representing custom HyperBus operations
    > + * @read16: read 16 bit of data to flash in a single burst. Used to read

    s/to flash/from flash/.

    [...]
    > +#endif /* __LINUX_MTD_HYPERBUS_H__ */

    I thought you agreed to add the #defines for the HF commands. Well, I can add them
    as well...

    MBR, Sergei

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