From: Marek Vasut <marex@denx.de>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>,
linux-mtd@lists.infradead.org,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-kernel@vger.kernel.org, Richard Weinberger <richard@nod.at>
Subject: Re: [PATCH v2] mtd: rawnand: denali: add more delays before latching incoming data
Date: Wed, 22 Apr 2020 17:37:47 +0200 [thread overview]
Message-ID: <95757315-9cf6-fbd8-af2d-3ac39753a757@denx.de> (raw)
In-Reply-To: <20200422173600.304c7cf2@xps13>
On 4/22/20 5:36 PM, Miquel Raynal wrote:
> Hi Marek,
>
> Marek Vasut <marex@denx.de> wrote on Wed, 22 Apr 2020 17:29:53 +0200:
>
>> On 3/17/20 8:18 AM, Masahiro Yamada wrote:
>>> The Denali IP have several registers to specify how many clock cycles
>>> should be waited between falling/rising signals. You can improve the
>>> NAND access performance by programming these registers with optimized
>>> values.
>>>
>>> Because struct nand_sdr_timings represents the device requirement
>>> in pico seconds, denali_setup_data_interface() computes the register
>>> values by dividing the device timings with the clock period.
>>>
>>> Marek Vasut reported this driver in the latest kernel does not work
>>> on his SOCFPGA board. (The on-board NAND chip is mode 5)
>>>
>>> The suspicious parameter is acc_clks, so this commit relaxes it.
>>>
>>> The Denali NAND Flash Memory Controller User's Guide describes this
>>> register as follows:
>>>
>>> acc_clks
>>> signifies the number of bus interface clk_x clock cycles,
>>> controller should wait from read enable going low to sending
>>> out a strobe of clk_x for capturing of incoming data.
>>>
>>> Currently, acc_clks is calculated only based on tREA, the delay on the
>>> chip side. This does not include additional delays that come from the
>>> data path on the PCB and in the SoC, load capacity of the pins, etc.
>>>
>>> This relatively becomes a big factor on faster timing modes like mode 5.
>>>
>>> Before supporting the ->setup_data_interface() hook (e.g. Linux 4.12),
>>> the Denali driver hacks acc_clks in a couple of ways [1] [2] to support
>>> the timing mode 5.
>>>
>>> We would not go back to the hard-coded acc_clks, but we need to include
>>> this factor into the delay somehow. Let's say the amount of the additional
>>> delay is 10000 pico sec.
>>>
>>> In the new calculation, acc_clks is determined by timings->tREA_max +
>>> data_setup_on_host.
>>>
>>> Also, prolong the RE# low period to make sure the data hold is met.
>>>
>>> Finally, re-center the data latch timing for extra safety.
>>>
>>> [1] https://github.com/torvalds/linux/blob/v4.12/drivers/mtd/nand/denali.c#L276
>>> [2] https://github.com/torvalds/linux/blob/v4.12/drivers/mtd/nand/denali.c#L282
>>>
>>> Reported-by: Marek Vasut <marex@denx.de>
>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>>
>> I tested it on the AV SoCFPGA, this seems to work, so feel free to apply.
>
>
> Great! Thanks a lot for testing, would you mind sending your Tested-by?
Lightly
Tested-by: Marek Vasut <marex@denx.de>
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next prev parent reply other threads:[~2020-04-22 15:38 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 7:18 [PATCH v2] mtd: rawnand: denali: add more delays before latching incoming data Masahiro Yamada
2020-04-22 15:29 ` Marek Vasut
2020-04-22 15:36 ` Miquel Raynal
2020-04-22 15:37 ` Marek Vasut [this message]
2020-05-10 20:06 ` Miquel Raynal
2021-06-30 18:47 ` Ralph Siemsen
2021-07-04 16:00 ` Masahiro Yamada
2021-07-05 14:48 ` Ralph Siemsen
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