linux-kernel - Re: [PATCH v7 3/5] mtd: Add support for HyperBus memory devices

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Date:   Mon, 24 Jun 2019 19:03:44 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Rob Herring <robh+dt@...nel.org>
CC:     <linux-mtd@...ts.infradead.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        <devicetree@...r.kernel.org>, Mason Yang <masonccyang@...c.com.tw>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 3/5] mtd: Add support for HyperBus memory devices



On 22/06/19 1:22 AM, Sergei Shtylyov wrote:
> 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/.

OK

[...]
>> 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/.
>

Will fix


> [...]
>> +#endif /* __LINUX_MTD_HYPERBUS_H__ */
> 
>    I thought you agreed to add the #defines for the HF commands. Well, I can add them
> as well...
> 

Sorry, I thought you were proposing to add them to your driver's header
file. Anyways, I think its better to add defines when there is an actual
user.

If there are no further comments, I will fixup things locally and queue
up for next release.

-- 
Regards
Vignesh