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SubjectRe: [PATCH v8 3/5] mtd: Add support for HyperBus memory devices
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Hello!

On 06/25/2019 10:57 AM, 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 with respect to bits per clock
> cycle. But HyperBus operates at >166MHz frequencies.
> 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/drivers/mtd/Makefile b/drivers/mtd/Makefile
> index 806287e80e84..62d649a959e2 100644
> --- a/drivers/mtd/Makefile
> +++ b/drivers/mtd/Makefile
> @@ -34,3 +34,4 @@ obj-y += chips/ lpddr/ maps/ devices/ nand/ tests/
>
> obj-$(CONFIG_MTD_SPI_NOR) += spi-nor/
> obj-$(CONFIG_MTD_UBI) += ubi/
> +obj-$(CONFIG_MTD_HYPERBUS) += hyperbus/
> diff --git a/drivers/mtd/hyperbus/Kconfig b/drivers/mtd/hyperbus/Kconfig
> new file mode 100644
> index 000000000000..98147e28caa0
> --- /dev/null
> +++ b/drivers/mtd/hyperbus/Kconfig
> @@ -0,0 +1,11 @@
> +menuconfig MTD_HYPERBUS
> + tristate "HyperBus support"
> + select MTD_CFI
> + select MTD_MAP_BANK_WIDTH_2
> + select MTD_CFI_AMDSTD
> + select MTD_COMPLEX_MAPPINGS
> + help
> + This is the framework for the HyperBus which can be used by
> + the HyperBus Controller driver to communicate with
> + HyperFlash. See Cypress HyperBus specification for more
> + details
> diff --git a/drivers/mtd/hyperbus/Makefile b/drivers/mtd/hyperbus/Makefile
> new file mode 100644
> index 000000000000..ca61dedd730d
> --- /dev/null
> +++ b/drivers/mtd/hyperbus/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_MTD_HYPERBUS) += hyperbus-core.o
> diff --git a/drivers/mtd/hyperbus/hyperbus-core.c b/drivers/mtd/hyperbus/hyperbus-core.c
> new file mode 100644
> index 000000000000..63a9e64895bc
> --- /dev/null
> +++ b/drivers/mtd/hyperbus/hyperbus-core.c
> @@ -0,0 +1,154 @@
[...]
> +int hyperbus_register_device(struct hyperbus_device *hbdev)
> +{
[...]
> + hbdev->mtd = do_map_probe("cfi_probe", map);
> + if (!hbdev->mtd) {
> + dev_err(dev, "probing of hyperbus device failed\n");
> + return -ENODEV;
> + }
> +
> + hbdev->mtd->dev.parent = dev;
> + mtd_set_of_node(hbdev->mtd, np);
> +
> + ret = mtd_device_register(hbdev->mtd, NULL, 0);
> + if (ret) {
> + dev_err(dev, "failed to register mtd device\n");
> + map_destroy(hbdev->mtd);
> + return ret;
> + }
> + hbdev->registered = true;

I doubt that you actually need this flag...

> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(hyperbus_register_device);
> +
> +int hyperbus_unregister_device(struct hyperbus_device *hbdev)
> +{
> + int ret = 0;
> +
> + if (hbdev && hbdev->mtd && hbdev->registered) {

... as you missed clearing that 'registered' flag.

> + ret = mtd_device_unregister(hbdev->mtd);
> + map_destroy(hbdev->mtd);
> + }
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(hyperbus_unregister_device);
[...]

MBR, Sergei

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