mtd: mxs_nand: Support EDO mode for imx8mn architecture

Add support for imx8mn architecture in order to run the NAND
in fast edo mode.

Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>

3 files changed, 242 insertions, 27 deletions

diff --git a/drivers/mtd/nand/raw/mxs_nand.c b/drivers/mtd/nand/raw/mxs_nand.c
index 7893e9d7e34..65eab4c8088 100644
--- a/drivers/mtd/nand/raw/mxs_nand.c
+++ b/drivers/mtd/nand/raw/mxs_nand.c
@@ -14,6 +14,7 @@
  */
 
 #include <common.h>
+#include <clk.h>
 #include <cpu_func.h>
 #include <dm.h>
 #include <dm/device_compat.h>
@@ -26,10 +27,12 @@
 #include <asm/io.h>
 #include <asm/mach-imx/regs-bch.h>
 #include <asm/mach-imx/regs-gpmi.h>
+#include <linux/delay.h>
 #include <linux/errno.h>
 #include <linux/mtd/rawnand.h>
 #include <linux/sizes.h>
 #include <linux/types.h>
+#include <linux/math64.h>
 
 #define	MXS_NAND_DMA_DESCRIPTOR_COUNT		4
 
@@ -49,6 +52,10 @@
 #endif
 
 #define	MXS_NAND_BCH_TIMEOUT			10000
+#define	USEC_PER_SEC				1000000
+#define	NSEC_PER_SEC				1000000000L
+
+#define TO_CYCLES(duration, period) DIV_ROUND_UP_ULL(duration, period)
 
 struct nand_ecclayout fake_ecc_layout;
 
@@ -1344,6 +1351,196 @@ err1:
 	return ret;
 }
 
+/*
+ * <1> Firstly, we should know what's the GPMI-clock means.
+ *     The GPMI-clock is the internal clock in the gpmi nand controller.
+ *     If you set 100MHz to gpmi nand controller, the GPMI-clock's period
+ *     is 10ns. Mark the GPMI-clock's period as GPMI-clock-period.
+ *
+ * <2> Secondly, we should know what's the frequency on the nand chip pins.
+ *     The frequency on the nand chip pins is derived from the GPMI-clock.
+ *     We can get it from the following equation:
+ *
+ *         F = G / (DS + DH)
+ *
+ *         F  : the frequency on the nand chip pins.
+ *         G  : the GPMI clock, such as 100MHz.
+ *         DS : GPMI_HW_GPMI_TIMING0:DATA_SETUP
+ *         DH : GPMI_HW_GPMI_TIMING0:DATA_HOLD
+ *
+ * <3> Thirdly, when the frequency on the nand chip pins is above 33MHz,
+ *     the nand EDO(extended Data Out) timing could be applied.
+ *     The GPMI implements a feedback read strobe to sample the read data.
+ *     The feedback read strobe can be delayed to support the nand EDO timing
+ *     where the read strobe may deasserts before the read data is valid, and
+ *     read data is valid for some time after read strobe.
+ *
+ *     The following figure illustrates some aspects of a NAND Flash read:
+ *
+ *                   |<---tREA---->|
+ *                   |             |
+ *                   |         |   |
+ *                   |<--tRP-->|   |
+ *                   |         |   |
+ *                  __          ___|__________________________________
+ *     RDN            \________/   |
+ *                                 |
+ *                                 /---------\
+ *     Read Data    --------------<           >---------
+ *                                 \---------/
+ *                                |     |
+ *                                |<-D->|
+ *     FeedbackRDN  ________             ____________
+ *                          \___________/
+ *
+ *          D stands for delay, set in the HW_GPMI_CTRL1:RDN_DELAY.
+ *
+ *
+ * <4> Now, we begin to describe how to compute the right RDN_DELAY.
+ *
+ *  4.1) From the aspect of the nand chip pins:
+ *        Delay = (tREA + C - tRP)               {1}
+ *
+ *        tREA : the maximum read access time.
+ *        C    : a constant to adjust the delay. default is 4000ps.
+ *        tRP  : the read pulse width, which is exactly:
+ *                   tRP = (GPMI-clock-period) * DATA_SETUP
+ *
+ *  4.2) From the aspect of the GPMI nand controller:
+ *         Delay = RDN_DELAY * 0.125 * RP        {2}
+ *
+ *         RP   : the DLL reference period.
+ *            if (GPMI-clock-period > DLL_THRETHOLD)
+ *                   RP = GPMI-clock-period / 2;
+ *            else
+ *                   RP = GPMI-clock-period;
+ *
+ *            Set the HW_GPMI_CTRL1:HALF_PERIOD if GPMI-clock-period
+ *            is greater DLL_THRETHOLD. In other SOCs, the DLL_THRETHOLD
+ *            is 16000ps, but in mx6q, we use 12000ps.
+ *
+ *  4.3) since {1} equals {2}, we get:
+ *
+ *                     (tREA + 4000 - tRP) * 8
+ *         RDN_DELAY = -----------------------     {3}
+ *                           RP
+ */
+static void mxs_compute_timings(struct nand_chip *chip,
+				const struct nand_sdr_timings *sdr)
+{
+	struct mxs_nand_info *nand_info = nand_get_controller_data(chip);
+	unsigned long clk_rate;
+	unsigned int dll_wait_time_us;
+	unsigned int dll_threshold_ps = nand_info->max_chain_delay;
+	unsigned int period_ps, reference_period_ps;
+	unsigned int data_setup_cycles, data_hold_cycles, addr_setup_cycles;
+	unsigned int tRP_ps;
+	bool use_half_period;
+	int sample_delay_ps, sample_delay_factor;
+	u16 busy_timeout_cycles;
+	u8 wrn_dly_sel;
+	u32 timing0;
+	u32 timing1;
+	u32 ctrl1n;
+
+	if (sdr->tRC_min >= 30000) {
+		/* ONFI non-EDO modes [0-3] */
+		clk_rate = 22000000;
+		wrn_dly_sel = GPMI_CTRL1_WRN_DLY_SEL_4_TO_8NS;
+	} else if (sdr->tRC_min >= 25000) {
+		/* ONFI EDO mode 4 */
+		clk_rate = 80000000;
+		wrn_dly_sel = GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY;
+		debug("%s, setting ONFI onfi edo 4\n", __func__);
+	} else {
+		/* ONFI EDO mode 5 */
+		clk_rate = 100000000;
+		wrn_dly_sel = GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY;
+		debug("%s, setting ONFI onfi edo 5\n", __func__);
+	}
+
+	/* SDR core timings are given in picoseconds */
+	period_ps = div_u64((u64)NSEC_PER_SEC * 1000, clk_rate);
+
+	addr_setup_cycles = TO_CYCLES(sdr->tALS_min, period_ps);
+	data_setup_cycles = TO_CYCLES(sdr->tDS_min, period_ps);
+	data_hold_cycles = TO_CYCLES(sdr->tDH_min, period_ps);
+	busy_timeout_cycles = TO_CYCLES(sdr->tWB_max + sdr->tR_max, period_ps);
+
+	timing0 = (addr_setup_cycles << GPMI_TIMING0_ADDRESS_SETUP_OFFSET) |
+		      (data_hold_cycles << GPMI_TIMING0_DATA_HOLD_OFFSET) |
+		      (data_setup_cycles << GPMI_TIMING0_DATA_SETUP_OFFSET);
+	timing1 = (busy_timeout_cycles * 4096) << GPMI_TIMING1_DEVICE_BUSY_TIMEOUT_OFFSET;
+
+	/*
+	 * Derive NFC ideal delay from {3}:
+	 *
+	 *                     (tREA + 4000 - tRP) * 8
+	 *         RDN_DELAY = -----------------------
+	 *                                RP
+	 */
+	if (period_ps > dll_threshold_ps) {
+		use_half_period = true;
+		reference_period_ps = period_ps / 2;
+	} else {
+		use_half_period = false;
+		reference_period_ps = period_ps;
+	}
+
+	tRP_ps = data_setup_cycles * period_ps;
+	sample_delay_ps = (sdr->tREA_max + 4000 - tRP_ps) * 8;
+	if (sample_delay_ps > 0)
+		sample_delay_factor = sample_delay_ps / reference_period_ps;
+	else
+		sample_delay_factor = 0;
+
+	ctrl1n = (wrn_dly_sel << GPMI_CTRL1_WRN_DLY_SEL_OFFSET);
+	if (sample_delay_factor)
+		ctrl1n |= (sample_delay_factor << GPMI_CTRL1_RDN_DELAY_OFFSET) |
+			GPMI_CTRL1_DLL_ENABLE |
+			(use_half_period ? GPMI_CTRL1_HALF_PERIOD : 0);
+
+	writel(timing0, &nand_info->gpmi_regs->hw_gpmi_timing0);
+	writel(timing1, &nand_info->gpmi_regs->hw_gpmi_timing1);
+
+	/*
+	 * Clear several CTRL1 fields, DLL must be disabled when setting
+	 * RDN_DELAY or HALF_PERIOD.
+	 */
+	writel(GPMI_CTRL1_CLEAR_MASK, &nand_info->gpmi_regs->hw_gpmi_ctrl1_clr);
+	writel(ctrl1n, &nand_info->gpmi_regs->hw_gpmi_ctrl1_set);
+
+	clk_set_rate(nand_info->gpmi_clk, clk_rate);
+
+	/* Wait 64 clock cycles before using the GPMI after enabling the DLL */
+	dll_wait_time_us = USEC_PER_SEC / clk_rate * 64;
+	if (!dll_wait_time_us)
+		dll_wait_time_us = 1;
+
+	/* Wait for the DLL to settle. */
+	udelay(dll_wait_time_us);
+}
+
+static int mxs_nand_setup_interface(struct mtd_info *mtd, int chipnr,
+				    const struct nand_data_interface *conf)
+{
+	struct nand_chip *chip = mtd_to_nand(mtd);
+	const struct nand_sdr_timings *sdr;
+
+	sdr = nand_get_sdr_timings(conf);
+	if (IS_ERR(sdr))
+		return PTR_ERR(sdr);
+
+	/* Stop here if this call was just a check */
+	if (chipnr < 0)
+		return 0;
+
+	/* Do the actual derivation of the controller timings */
+	mxs_compute_timings(chip, sdr);
+
+	return 0;
+}
+
 int mxs_nand_init_spl(struct nand_chip *nand)
 {
 	struct mxs_nand_info *nand_info;
@@ -1432,6 +1629,9 @@ int mxs_nand_init_ctrl(struct mxs_nand_info *nand_info)
 	nand->read_buf		= mxs_nand_read_buf;
 	nand->write_buf		= mxs_nand_write_buf;
 
+	if (nand_info->gpmi_clk)
+		nand->setup_data_interface = mxs_nand_setup_interface;
+
 	/* first scan to find the device and get the page size */
 	if (nand_scan_ident(mtd, CONFIG_SYS_MAX_NAND_DEVICE, NULL))
 		goto err_free_buffers;
diff --git a/drivers/mtd/nand/raw/mxs_nand_dt.c b/drivers/mtd/nand/raw/mxs_nand_dt.c
index 94ee7ed9ec8..a922a22b273 100644
--- a/drivers/mtd/nand/raw/mxs_nand_dt.c
+++ b/drivers/mtd/nand/raw/mxs_nand_dt.c
@@ -22,22 +22,27 @@
 
 struct mxs_nand_dt_data {
 	unsigned int max_ecc_strength_supported;
+	int max_chain_delay; /* See the async EDO mode */
 };
 
 static const struct mxs_nand_dt_data mxs_nand_imx6q_data = {
 	.max_ecc_strength_supported = 40,
+	.max_chain_delay = 12000,
 };
 
 static const struct mxs_nand_dt_data mxs_nand_imx6sx_data = {
 	.max_ecc_strength_supported = 62,
+	.max_chain_delay = 12000,
 };
 
 static const struct mxs_nand_dt_data mxs_nand_imx7d_data = {
 	.max_ecc_strength_supported = 62,
+	.max_chain_delay = 12000,
 };
 
 static const struct mxs_nand_dt_data mxs_nand_imx8qxp_data = {
 	.max_ecc_strength_supported = 62,
+	.max_chain_delay = 12000,
 };
 
 static const struct udevice_id mxs_nand_dt_ids[] = {
@@ -72,8 +77,10 @@ static int mxs_nand_dt_probe(struct udevice *dev)
 	int ret;
 
 	data = (void *)dev_get_driver_data(dev);
-	if (data)
+	if (data) {
 		info->max_ecc_strength_supported = data->max_ecc_strength_supported;
+		info->max_chain_delay = data->max_chain_delay;
+	}
 
 	info->dev = dev;
 
@@ -92,44 +99,49 @@ static int mxs_nand_dt_probe(struct udevice *dev)
 
 	info->use_minimum_ecc = dev_read_bool(dev, "fsl,use-minimum-ecc");
 
-	if (IS_ENABLED(CONFIG_CLK) && IS_ENABLED(CONFIG_IMX8)) {
+	if (IS_ENABLED(CONFIG_CLK) &&
+	    (IS_ENABLED(CONFIG_IMX8) || IS_ENABLED(CONFIG_IMX8M))) {
 		/* Assigned clock already set clock */
 		struct clk gpmi_clk;
 
-		ret = clk_get_by_name(dev, "gpmi_io", &gpmi_clk);
-		if (ret < 0) {
+		info->gpmi_clk = devm_clk_get(dev, "gpmi_io");
+
+		if (IS_ERR(info->gpmi_clk)) {
+			ret = PTR_ERR(info->gpmi_clk);
 			debug("Can't get gpmi io clk: %d\n", ret);
 			return ret;
 		}
 
-		ret = clk_enable(&gpmi_clk);
+		ret = clk_enable(info->gpmi_clk);
 		if (ret < 0) {
 			debug("Can't enable gpmi io clk: %d\n", ret);
 			return ret;
 		}
 
-		ret = clk_get_by_name(dev, "gpmi_apb", &gpmi_clk);
-		if (ret < 0) {
-			debug("Can't get gpmi_apb clk: %d\n", ret);
-			return ret;
-		}
-
-		ret = clk_enable(&gpmi_clk);
-		if (ret < 0) {
-			debug("Can't enable gpmi_apb clk: %d\n", ret);
-			return ret;
-		}
-
-		ret = clk_get_by_name(dev, "gpmi_bch", &gpmi_clk);
-		if (ret < 0) {
-			debug("Can't get gpmi_bch clk: %d\n", ret);
-			return ret;
-		}
-
-		ret = clk_enable(&gpmi_clk);
-		if (ret < 0) {
-			debug("Can't enable gpmi_bch clk: %d\n", ret);
-			return ret;
+		if (IS_ENABLED(CONFIG_IMX8)) {
+			ret = clk_get_by_name(dev, "gpmi_apb", &gpmi_clk);
+			if (ret < 0) {
+				debug("Can't get gpmi_apb clk: %d\n", ret);
+				return ret;
+			}
+
+			ret = clk_enable(&gpmi_clk);
+			if (ret < 0) {
+				debug("Can't enable gpmi_apb clk: %d\n", ret);
+				return ret;
+			}
+
+			ret = clk_get_by_name(dev, "gpmi_bch", &gpmi_clk);
+			if (ret < 0) {
+				debug("Can't get gpmi_bch clk: %d\n", ret);
+				return ret;
+			}
+
+			ret = clk_enable(&gpmi_clk);
+			if (ret < 0) {
+				debug("Can't enable gpmi_bch clk: %d\n", ret);
+				return ret;
+			}
 		}
 
 		ret = clk_get_by_name(dev, "gpmi_bch_apb", &gpmi_clk);
diff --git a/include/mxs_nand.h b/include/mxs_nand.h
index 741dc8734ea..bb5b84b8c26 100644
--- a/include/mxs_nand.h
+++ b/include/mxs_nand.h
@@ -12,6 +12,7 @@
 #include <asm/cache.h>
 #include <nand.h>
 #include <asm/mach-imx/dma.h>
+#include <clk.h>
 
 /**
  * @gf_len:                   The length of Galois Field. (e.g., 13 or 14)
@@ -43,6 +44,7 @@ struct mxs_nand_info {
 	struct nand_chip chip;
 	struct udevice *dev;
 	unsigned int	max_ecc_strength_supported;
+	int		max_chain_delay;
 	bool		use_minimum_ecc;
 	int		cur_chip;
 
@@ -59,6 +61,7 @@ struct mxs_nand_info {
 
 	struct mxs_gpmi_regs *gpmi_regs;
 	struct mxs_bch_regs *bch_regs;
+	struct clk *gpmi_clk;
 
 	/* Functions with altered behaviour */
 	int		(*hooked_read_oob)(struct mtd_info *mtd,