linux-kernel - Re: [PATCH v2 2/3] mtd: spi-nor: Altera ASMI Parallel II IP Core

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Date:   Wed, 11 Oct 2017 23:06:02 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     matthew.gerlach@...ux.intel.com
Cc:     vndao@...era.com, dwmw2@...radead.org, computersforpeace@...il.com,
        boris.brezillon@...e-electrons.com, richard@....at,
        cyrille.pitchen@...ev4u.fr, robh+dt@...nel.org,
        mark.rutland@....com, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, davem@...emloft.net,
        mchehab@...nel.org, linux-fpga@...r.kernel.org,
        tien.hock.loh@...el.com, hean.loong.ong@...el.com
Subject: Re: [PATCH v2 2/3] mtd: spi-nor: Altera ASMI Parallel II IP Core

On 10/11/2017 07:00 PM, matthew.gerlach@...ux.intel.com wrote:
> 
> 
> On Tue, 10 Oct 2017, Marek Vasut wrote:
> 
>> On 09/20/2017 08:28 PM, matthew.gerlach@...ux.intel.com wrote:
>>> From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
>>>
>>> This patch adds support for a spi-nor, platform driver for the
>>> Altera ASMI Parallel II IP Core.  The intended use case is to be able
>>> to update the flash used to load a FPGA at power up with mtd-utils.
>>>
>>> Signed-off-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
>>> ---
>>> v2:
>>>     minor checkpatch fixing by Wu Hao <hao.wu@...el.com>
>>>     Use read_dummy value as suggested by Cyrille Pitchen.
>>>     Don't assume 4 byte addressing (Cryille Pichecn and Marek Vasut).
>>>     Fixed #define indenting as suggested by Marek Vasut.
>>>     Added units to timer values as suggested by Marek Vasut.
>>>     Use io(read|write)8_rep() as suggested by Marek Vasut.
>>>     Renamed function prefixed with __ as suggested by Marek Vasut.
>>
>> [...]
>>
>>> +#define QSPI_ACTION_REG            0
>>> +#define QSPI_ACTION_RST            BIT(0)
>>> +#define QSPI_ACTION_EN            BIT(1)
>>> +#define QSPI_ACTION_SC            BIT(2)
>>> +#define QSPI_ACTION_CHIP_SEL_SFT    4
>>> +#define QSPI_ACTION_DUMMY_SFT        8
>>> +#define QSPI_ACTION_READ_BACK_SFT    16
>>> +
>>> +#define QSPI_FIFO_CNT_REG        4
>>> +#define QSPI_FIFO_DEPTH            0x200
>>> +#define QSPI_FIFO_CNT_MSK        0x3ff
>>> +#define QSPI_FIFO_CNT_RX_SFT        0
>>> +#define QSPI_FIFO_CNT_TX_SFT        12
>>> +
>>> +#define QSPI_DATA_REG            0x8
>>> +
>>> +#define QSPI_POLL_TIMEOUT_US        10000000
>>
>> 10 s poll timeout ? :)
> 
> Hi Marek,
> 
> The 10s timeout is fairly arbitrary.  In other words, I pulled it out of
> thin air.  Can you suggest a better timeout?  From a practical
> standpoint 10s seemed to be much better than no timeout when I was
> debugging bad FPGA images.  Without a timeout I was hanging the system
> when the FPGA image failed.  With this timeout, we get a nice message
> and Linux keeps running happily.
AFAIK the SPI subsystem has a timeout which is adaptive to the bus
clock, maybe that's what you want to use here ?

-- 
Best regards,
Marek Vasut