[PATCH 3/7] mtd: nand: automate NAND timings selection
Boris Brezillon
boris.brezillon at free-electrons.com
Wed Sep 7 08:59:17 PDT 2016
On Wed, 7 Sep 2016 16:59:51 +0200
Boris Brezillon <boris.brezillon at free-electrons.com> wrote:
> On Wed, 7 Sep 2016 16:36:15 +0200
> Sascha Hauer <s.hauer at pengutronix.de> wrote:
>
> > On Wed, Sep 07, 2016 at 03:41:14PM +0200, Boris Brezillon wrote:
> > > On Wed, 7 Sep 2016 14:21:38 +0200
> > > Sascha Hauer <s.hauer at pengutronix.de> wrote:
> > >
> > > > From: Boris Brezillon <boris.brezillon at free-electrons.com>
> > > >
> > > > The NAND framework provides several helpers to query timing modes supported
> > > > by a NAND chip, but this implies that all NAND controller drivers have
> > > > to implement the same timings selection dance. Also currently NAND
> > > > devices can be resetted at arbitrary places which also resets the timing
> > > > for ONFI chips to timing mode 0.
> > > >
> > > > Provide a common logic to select the best timings based on ONFI or
> > > > ->onfi_timing_mode_default information. Hook this into nand_reset()
> > > > to make sure the new timing is applied each time during a reset.
> > > >
> > > > NAND controller willing to support timings adjustment should just
> > > > implement the ->setup_data_interface() method.
> > > >
> > > > Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
> > > > Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> > > > ---
> > > > drivers/mtd/nand/nand_base.c | 134 +++++++++++++++++++++++++++++++++++++++++++
> > > > include/linux/mtd/nand.h | 12 ++--
> > > > 2 files changed, 142 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> > > > index 1f704cc..c9bc988 100644
> > > > --- a/drivers/mtd/nand/nand_base.c
> > > > +++ b/drivers/mtd/nand/nand_base.c
> > > > @@ -948,6 +948,130 @@ static int nand_wait(struct mtd_info *mtd, struct nand_chip *chip)
> > > > }
> > > >
> > > > /**
> > > > + * nand_reset_data_interface - Reset data interface and timings
> > > > + * @chip: The NAND chip
> > > > + *
> > > > + * Reset the Data interface and timings to ONFI mode 0.
> > > > + *
> > > > + * Returns 0 for success or negative error code otherwise.
> > > > + */
> > > > +static int nand_reset_data_interface(struct nand_chip *chip)
> > > > +{
> > > > + struct mtd_info *mtd = &chip->mtd;
> > > > + struct nand_data_interface *conf;
> > > > + int ret;
> > > > +
> > > > + if (!chip->setup_data_interface)
> > > > + return 0;
> > > > +
> > > > + conf = kzalloc(sizeof(*conf), GFP_KERNEL);
> > > > + if (!conf)
> > > > + return -ENOMEM;
> > > > +
> > > > + /*
> > > > + * The ONFI specification says:
> > > > + * "
> > > > + * To transition from NV-DDR or NV-DDR2 to the SDR data
> > > > + * interface, the host shall use the Reset (FFh) command
> > > > + * using SDR timing mode 0. A device in any timing mode is
> > > > + * required to recognize Reset (FFh) command issued in SDR
> > > > + * timing mode 0.
> > > > + * "
> > > > + *
> > > > + * Configure the data interface in SDR mode and set the
> > > > + * timings to timing mode 0.
> > > > + */
> > > > +
> > > > + conf->type = NAND_SDR_IFACE,
> > > > + conf->timings.sdr = *onfi_async_timing_mode_to_sdr_timings(0);
> > > > +
> > > > + ret = chip->setup_data_interface(mtd, conf, false);
> > > > + if (ret)
> > > > + pr_err("Failed to configure data interface to SDR timing mode 0\n");
> > >
> > > I just realized that going back to timing mode 0 is not needed if your
> > > chip is not ONFI or JEDEC compliant. But that's not really an issue.
> > >
> > > > +
> > > > + kfree(conf);
> > > > +
> > > > + return ret;
> > > > +}
> > > > +
> > > > +/**
> > > > + * nand_setup_data_interface - Setup the best data interface and timings
> > > > + * @chip: The NAND chip
> > > > + *
> > > > + * Find and configure the best data interface and NAND timings supported by
> > > > + * the chip and the driver.
> > > > + * First tries to retrieve supported timing modes from ONFI information,
> > > > + * and if the NAND chip does not support ONFI, relies on the
> > > > + * ->onfi_timing_mode_default specified in the nand_ids table.
> > > > + *
> > > > + * Returns 0 for success or negative error code otherwise.
> > > > + */
> > > > +static int nand_setup_data_interface(struct nand_chip *chip)
> > > > +{
> > > > + struct mtd_info *mtd = &chip->mtd;
> > > > + struct nand_data_interface *conf;
> > > > + int modes, mode, ret;
> > > > +
> > > > + if (!chip->setup_data_interface)
> > > > + return 0;
> > > > +
> > > > + /*
> > > > + * First try to identify the best timings from ONFI parameters and
> > > > + * if the NAND does not support ONFI, fallback to the default ONFI
> > > > + * timing mode.
> > > > + */
> > > > + modes = onfi_get_async_timing_mode(chip);
> > > > + if (modes == ONFI_TIMING_MODE_UNKNOWN) {
> > > > + if (!chip->onfi_timing_mode_default)
> > > > + return 0;
> > > > +
> > > > + modes = GENMASK(chip->onfi_timing_mode_default, 0);
> > > > + }
> > >
> > > This implementation is assuming the chip is either ONFI compliant or
> > > not compliant with JEDEC and ONFI, but JEDEC chips also provides
> > > 'timing modes', except it's called 'speed grades'. Not sure how they
> > > match to the ONFI timing modes, and I'm definitely not asking you to
> > > support that right now, but that would be good to split the different
> > > cases (ONFI compliant, JEDEC compliant and not compliant with JEDEC or
> > > ONFI) in different functions.
> > >
> > > Those functions would just fill in the nand_data_interface object, and
> > > nand_setup_data_interface() (or nand_select_data_interface(), if we
> > > decide to split the logic in 2 different functions as suggested below)
> > > would call one of them depending on the ->{jedec,onfo}_version values.
> > >
> > > > +
> > > > + conf = kzalloc(sizeof(*conf), GFP_KERNEL);
> > > > + if (!conf)
> > > > + return -ENOMEM;
> > > > +
> > > > + ret = -EINVAL;
> > > > + for (mode = fls(modes) - 1; mode >= 0; mode--) {
> > > > + conf->type = NAND_SDR_IFACE,
> > > > + conf->timings.sdr = *onfi_async_timing_mode_to_sdr_timings(mode);
> > > > +
> > > > + ret = chip->setup_data_interface(mtd, conf, true);
> > > > + if (!ret) {
> > > > + chip->onfi_timing_mode_default = mode;
> > > > + break;
> > > > + }
> > > > + }
> > > > +
> > > > + if (ret)
> > > > + goto err;
> > >
> > > The data interface config selection only has to be done once: when you
> > > discover/init the chip...
> > >
> > > > +
> > > > + /*
> > > > + * Ensure the timing mode has been changed on the chip side
> > > > + * before changing timings on the controller side.
> > > > + */
> > > > + if (chip->onfi_version) {
> > > > + uint8_t tmode_param[ONFI_SUBFEATURE_PARAM_LEN] = {
> > > > + chip->onfi_timing_mode_default,
> > > > + };
> > > > +
> > > > + ret = chip->onfi_set_features(mtd, chip,
> > > > + ONFI_FEATURE_ADDR_TIMING_MODE,
> > > > + tmode_param);
> > > > + if (ret)
> > > > + goto err;
> > > > + }
> > > > +
> > > > + ret = chip->setup_data_interface(mtd, conf, false);
> > >
> > > ... but the setup will be done each time you reset the chip.
> > >
> > > Maybe that's what you were trying to explain me yesterday.
> >
> > Indeed.
> >
> > >
> > > Anyway, I really think we should keep the default/best data interface
> > > config in nand_chip so that we can later re-use it without have to go
> > > through the supported timing detection logic.
> >
> > Ok, I think now we are understanding each other. So I keep two timing
> > instances in struct nand_chip, one for initialization and one optimized
> > timing. They both get initialized once during chip detection and can be
> > reused when needed.
>
> Hm, not sure we need to keep 2 instances around, all we need to save is
> the 'best_onfi_timing_mode', or we can just update
> ->default_onfi_timing_mode based on the result of the timing mode
> detection, so that, when nand_setup_data_interface() is called, all we
> have to do is:
>
> conf = chip->data_iface_conf;
> conf->type = NAND_SDR_IFACE,
> conf->timings.sdr = *onfi_async_timing_mode_to_sdr_timings(chip->default_onfi_timing_mode);
> chip->setup_data_interface(mtd, conf, false);
>
After the discussion we had on IRC, I want to reconsider what I said.
How about having a global nand_default_data_iface_config that would
work will all chips (probably exposing mode 0 timings and an SDR
interface).
This one will be used even for DDR NANDs, because after a reset they
return back to SDR mode, timing mode 0.
Now, I keep thinking that other timing modes should not be directly
exposed.
Doing that should solve the problem you mentioned: when interacting with
multi-dies chips, chip->data_iface content is changed N times from mode
0 to mode X during a reset (where N is the number of dies in your chip).
Let me know what you think.
More information about the linux-arm-kernel
mailing list