From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Marek Vasut <marex@denx.de>
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 17:36:00 +0200 [thread overview]
Message-ID: <20200422173600.304c7cf2@xps13> (raw)
In-Reply-To: <6093dfab-1e9e-824a-b639-33d340b377f9@denx.de>
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?
Thanks,
Miquèl
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next prev parent reply other threads:[~2020-04-22 15:36 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 [this message]
2020-04-22 15:37 ` Marek Vasut
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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