From: Dario Binacchi dario.binacchi@amarulasolutions.com
[ Upstream commit 15e27d197a7ea69b4643791ca2f8467fdd998359 ]
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 to set edo mode 5 (100MHz) but the rate returned by clk_round_rate() is 80MHz (edo mode 4). In this case gpmi_nfc_compute_timings() will return error, and will be called again to set edo mode 4, 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 Tested-by: Sascha Hauer s.hauer@pengutronix.de Reviewed-by: Sascha Hauer s.hauer@pengutronix.de Signed-off-by: Miquel Raynal miquel.raynal@bootlin.com Link: https://lore.kernel.org/linux-mtd/20220118095434.35081-4-dario.binacchi@amar... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 22 ++++++++++++++++++---- 1 file changed, 18 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 b72b387c08ef..62f4988c2a5f 100644 --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c @@ -644,8 +644,8 @@ static int bch_set_geometry(struct gpmi_nand_data *this) * 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; @@ -657,23 +657,33 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this, int sample_delay_ps, sample_delay_factor; u16 busy_timeout_cycles; u8 wrn_dly_sel; + unsigned long clk_rate, min_rate;
if (sdr->tRC_min >= 30000) { /* ONFI non-EDO modes [0-3] */ hw->clk_rate = 22000000; + min_rate = 0; wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_4_TO_8NS; } else if (sdr->tRC_min >= 25000) { /* ONFI EDO mode 4 */ hw->clk_rate = 80000000; + min_rate = 22000000; wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY; } else { /* ONFI EDO mode 5 */ hw->clk_rate = 100000000; + min_rate = 80000000; wrn_dly_sel = BV_GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY; }
- hw->clk_rate = clk_round_rate(r->clock[0], hw->clk_rate); + clk_rate = clk_round_rate(r->clock[0], hw->clk_rate); + if (clk_rate <= min_rate) { + dev_err(this->dev, "clock setting: expected %ld, got %ld\n", + hw->clk_rate, clk_rate); + return -ENOTSUPP; + }
+ hw->clk_rate = clk_rate; /* SDR core timings are given in picoseconds */ period_ps = div_u64((u64)NSEC_PER_SEC * 1000, hw->clk_rate);
@@ -714,6 +724,7 @@ 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) @@ -769,6 +780,7 @@ 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); @@ -784,7 +796,9 @@ 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;