From: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
To: Vignesh Raghavendra <vigneshr@ti.com>,
Boris Brezillon <bbrezillon@kernel.org>,
Marek Vasut <marek.vasut@gmail.com>,
Richard Weinberger <richard@nod.at>,
Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org,
Tokunori Ikegami <ikegami.t@gmail.com>,
linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org,
Miquel Raynal <miquel.raynal@bootlin.com>,
Mason Yang <masonccyang@mxic.com.tw>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v8 3/5] mtd: Add support for HyperBus memory devices
Date: Wed, 3 Jul 2019 21:14:01 +0300 [thread overview]
Message-ID: <8e870356-90ba-4762-b1fd-8a13ce6ebcc8@cogentembedded.com> (raw)
In-Reply-To: <5009c418-a051-a42a-f78a-360f7230dd2b@ti.com>
Hello!
On 07/03/2019 07:41 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>
>> [...]
>>
>> I have at least created my HyperBus driver and unfortunately I'm having serious
At last. :-)
>> issues with the design of the support core (see below)...
>>
>> [...]
>>> 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)
>>> +{
>>> + const struct hyperbus_ops *ops;
>>> + struct hyperbus_ctlr *ctlr;
>>> + struct device_node *np;
>>> + struct map_info *map;
>>> + struct resource res;
>>> + struct device *dev;
>>> + int ret;
>>> +
>>> + if (!hbdev || !hbdev->np || !hbdev->ctlr || !hbdev->ctlr->dev) {
>>> + pr_err("hyperbus: please fill all the necessary fields!\n");
>>> + return -EINVAL;
>>> + }
>>> +
>>> + np = hbdev->np;
>>> + ctlr = hbdev->ctlr;
>>> + if (!of_device_is_compatible(np, "cypress,hyperflash"))
>>> + return -ENODEV;
>>> +
>>> + hbdev->memtype = HYPERFLASH;
>>> +
>>> + ret = of_address_to_resource(np, 0, &res);
>>
>> Hm, I doubt that the HB devices are wholly mapped into memory space, that seems
>> like a property of the HB controller. In my case, the flash device in the DT has
>> only single-cell "reg" prop (equal to the chip select #). Then this function returns
>> -EINVAL and the registration fails. Also, in my case such mapping is R/O, not R/W.
>>
>
> You could declare R/O MMIO region in controla and set up a translation using ranges
> from slave's reg CS based reg mapping like:
No, not all HB controllers work the same (simple) way as yours. In case of RPC-IF,
the direct read map is a 64 MiB window into a possibly larger flash chip, it has a
register supplying address bits 25:31...
> + hbmc: hyperbus@47034000 {
> + compatible = "ti,am654-hbmc";
> + reg = <0x0 0x47034000 0x0 0x100>,
> + <0x5 0x00000000 0x1 0x0000000>;
> + #address-cells = <2>;
> + #size-cells = <1>;
> + ranges = <0x0 0x0 0x5 0x00000000 0x4000000>, /* CS0 - 64MB */
> + <0x1 0x0 0x5 0x04000000 0x4000000>; /* CS1 - 64MB */
> +
> + /* Slave flash node */
> + flash@0,0 {
> + compatible = "cypress,hyperflash", "cfi-flash";
> + reg = <0x0 0x0 0x4000000>;
> + };
> + };
>
> If you use just CS# how would you handle CS to MMIO region mapping?
> Does both CS use the same MMIO base for reads?
The RPC-IF HF mode only has a single CS signal.
[...]
MBR, Sergei
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next prev parent reply other threads:[~2019-07-03 18:14 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-25 7:57 [PATCH v8 0/5] MTD: Add Initial Hyperbus support Vignesh Raghavendra
2019-06-25 7:57 ` [PATCH v8 1/5] mtd: cfi_cmdset_0002: Add support for polling status register Vignesh Raghavendra
2019-06-25 17:01 ` Tokunori Ikegami
2019-06-26 6:17 ` Vignesh Raghavendra
2019-06-25 7:57 ` [PATCH v8 2/5] dt-bindings: mtd: Add binding documentation for HyperFlash Vignesh Raghavendra
2019-06-25 7:57 ` [PATCH v8 3/5] mtd: Add support for HyperBus memory devices Vignesh Raghavendra
2019-06-25 20:00 ` Sergei Shtylyov
2019-07-02 17:53 ` Sergei Shtylyov
2019-07-03 4:41 ` Vignesh Raghavendra
2019-07-03 18:14 ` Sergei Shtylyov [this message]
2019-07-04 18:35 ` Vignesh Raghavendra
2019-07-11 19:26 ` Sergei Shtylyov
2019-07-12 4:52 ` Vignesh Raghavendra
2022-06-27 15:28 ` Geert Uytterhoeven
2022-07-02 17:10 ` Raghavendra, Vignesh
2022-07-03 8:33 ` Geert Uytterhoeven
2019-06-25 7:57 ` [PATCH v8 4/5] dt-bindings: mtd: Add bindings for TI's AM654 HyperBus memory controller Vignesh Raghavendra
2019-06-25 7:57 ` [PATCH v8 5/5] mtd: hyperbus: Add driver for TI's " Vignesh Raghavendra
2019-06-28 14:35 ` [PATCH v8 0/5] MTD: Add Initial Hyperbus support Vignesh Raghavendra
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