Messages in this thread Patch in this message | | | From | Dario Binacchi <> | Subject | [RFC PATCH v2 4/5] mtd: rawnand: gpmi: validate controller clock rate | Date | Mon, 17 Jan 2022 12:18:28 +0100 |
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What to do when the real rate of the gpmi clock is not equal to the required one? The solutions proposed in [1] did not lead to a conclusion on how to validate the clock rate, so, inspired by the document [2], I consider the rate correct only if not lower or equal to the rate of the previous edo mode. In fact, in chapter 4.16.2 (NV-DDR) of the document [2], it is written that "If the host selects timing mode n, then its clock period shall be faster than the clock period of timing mode n-1 and slower than or equal to the clock period of timing mode n.". I thought that it could therefore also be used in this case, without therefore having to define the valid rate ranges empirically.
For example, suppose that gpmi_nfc_compute_timings() is called for edo mode 5 configuration (100MHz, from the `edo_modes' table) but the rate returned by clk_round_rate() is 80MHz (edo mode 4 from the `edo_modes' table). In this case gpmi_nfc_compute_timings() will return error, and will be called again for edo mode 4 configuration, which this time will be successful.
[1] https://lore.kernel.org/r/20210702065350.209646-5-ebiggers@kernel.org [2] http://www.onfi.org/-/media/client/onfi/specs/onfi_3_0_gold.pdf?la=en
Co-developed-by: Michael Trimarchi <michael@amarulasolutions.com> Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com> Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
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Changes in v2: - Fix commit description. - Add an example to the commit description to better understand the problem solved by the patch. - Split the patch.
drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 24 ++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c index 4ac695aa5131..7ae7a37775a3 100644 --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c @@ -665,8 +665,8 @@ static const struct edo_mode edo_modes[] = { * RDN_DELAY = ----------------------- {3} * RP */ -static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this, - const struct nand_sdr_timings *sdr) +static int gpmi_nfc_compute_timings(struct gpmi_nand_data *this, + const struct nand_sdr_timings *sdr) { struct gpmi_nfc_hardware_timing *hw = &this->hw; struct resources *r = &this->resources; @@ -679,6 +679,7 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this, u16 busy_timeout_cycles; u8 wrn_dly_sel; int i, emode = ARRAY_SIZE(edo_modes) - 1; + long clk_rate; /* Search the required EDO mode */ for (i = 0; i < ARRAY_SIZE(edo_modes); i++) { @@ -688,7 +689,18 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this, } } - hw->clk_rate = clk_round_rate(r->clock[0], edo_modes[emode].clk_rate); + clk_rate = clk_round_rate(r->clock[0], edo_modes[emode].clk_rate); + if (emode > 0 && !(clk_rate <= edo_modes[emode].clk_rate && + clk_rate > edo_modes[emode - 1].clk_rate)) { + dev_err(this->dev, + "edo mode %d clock setting: expected %ld, got %ld\n", + emode, edo_modes[emode].clk_rate, clk_rate); + return -ENOTSUPP; + } + + dev_dbg(this->dev, "edo mode %d @ %ld Hz\n", emode, clk_rate); + + hw->clk_rate = clk_rate; wrn_dly_sel = edo_modes[emode].wrn_dly_sel; /* SDR core timings are given in picoseconds */ @@ -731,6 +743,7 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this, hw->ctrl1n |= BF_GPMI_CTRL1_RDN_DELAY(sample_delay_factor) | BM_GPMI_CTRL1_DLL_ENABLE | (use_half_period ? BM_GPMI_CTRL1_HALF_PERIOD : 0); + return 0; } static int gpmi_nfc_apply_timings(struct gpmi_nand_data *this) @@ -786,6 +799,7 @@ static int gpmi_setup_interface(struct nand_chip *chip, int chipnr, { struct gpmi_nand_data *this = nand_get_controller_data(chip); const struct nand_sdr_timings *sdr; + int ret; /* Retrieve required NAND timings */ sdr = nand_get_sdr_timings(conf); @@ -801,7 +815,9 @@ static int gpmi_setup_interface(struct nand_chip *chip, int chipnr, return 0; /* Do the actual derivation of the controller timings */ - gpmi_nfc_compute_timings(this, sdr); + ret = gpmi_nfc_compute_timings(this, sdr); + if (ret) + return ret; this->hw.must_apply_timings = true; -- 2.32.0
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