[PATCH linux dev-4.10 6/6] mtd: spi-nor: aspeed: optimize read mode

Cédric Le Goater clg at kaod.org
Sat Mar 25 01:44:43 AEDT 2017


Only for SPI controllers as U-Boot should have done it already for the
FMC controller using DMAs.

The algo first reads a golden buffer at low speed and then performs
reads with different clocks and delay cycles settings to find the
fastest configuration for the chip.

Based on the pflash tool.

Signed-off-by: Cédric Le Goater <clg at kaod.org>
---

 TODO: may be add a chicken switch ? 

 drivers/mtd/spi-nor/aspeed-smc.c | 185 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 185 insertions(+)

diff --git a/drivers/mtd/spi-nor/aspeed-smc.c b/drivers/mtd/spi-nor/aspeed-smc.c
index 1b398303f039..c89e935f9a7a 100644
--- a/drivers/mtd/spi-nor/aspeed-smc.c
+++ b/drivers/mtd/spi-nor/aspeed-smc.c
@@ -22,6 +22,7 @@
 #include <linux/mtd/spi-nor.h>
 #include <linux/of.h>
 #include <linux/of_platform.h>
+#include <linux/slab.h>
 #include <linux/sysfs.h>
 
 #define DEVICE_NAME	"aspeed-smc"
@@ -43,13 +44,17 @@ struct aspeed_smc_info {
 	bool hastype;		/* flash type field exists in config reg */
 	u8 we0;			/* shift for write enable bit for CE0 */
 	u8 ctl0;		/* offset in regs of ctl for CE0 */
+	u8 timing;		/* offset in regs of timing */
 	bool has_dma;
 
 	void (*set_4b)(struct aspeed_smc_chip *chip);
+	int (*optimize_reads)(struct aspeed_smc_chip *chip, u32 max_freq);
 };
 
 static void aspeed_smc_chip_set_4b_spi_2400(struct aspeed_smc_chip *chip);
 static void aspeed_smc_chip_set_4b(struct aspeed_smc_chip *chip);
+static int aspeed_smc_optimize_reads(struct aspeed_smc_chip *chip,
+				     u32 max_freq);
 
 static const struct aspeed_smc_info fmc_2400_info = {
 	.maxsize = 256 * 1024 * 1024,
@@ -57,6 +62,7 @@ static const struct aspeed_smc_info fmc_2400_info = {
 	.hastype = true,
 	.we0 = 16,
 	.ctl0 = 0x10,
+	.timing = 0x94,
 	.has_dma = true,
 	.set_4b = aspeed_smc_chip_set_4b,
 };
@@ -67,8 +73,10 @@ static const struct aspeed_smc_info spi_2400_info = {
 	.hastype = false,
 	.we0 = 0,
 	.ctl0 = 0x04,
+	.timing = 0x94,
 	.has_dma = false,
 	.set_4b = aspeed_smc_chip_set_4b_spi_2400,
+	.optimize_reads = aspeed_smc_optimize_reads,
 };
 
 static const struct aspeed_smc_info fmc_2500_info = {
@@ -77,6 +85,7 @@ static const struct aspeed_smc_info fmc_2500_info = {
 	.hastype = true,
 	.we0 = 16,
 	.ctl0 = 0x10,
+	.timing = 0x94,
 	.has_dma = true,
 	.set_4b = aspeed_smc_chip_set_4b,
 };
@@ -87,8 +96,10 @@ static const struct aspeed_smc_info spi_2500_info = {
 	.hastype = false,
 	.we0 = 16,
 	.ctl0 = 0x10,
+	.timing = 0x94,
 	.has_dma = false,
 	.set_4b = aspeed_smc_chip_set_4b,
+	.optimize_reads = aspeed_smc_optimize_reads,
 };
 
 enum aspeed_smc_ctl_reg_value {
@@ -865,6 +876,174 @@ static int aspeed_smc_chip_setup_init(struct aspeed_smc_chip *chip,
 	return 0;
 }
 
+
+#define CALIBRATE_BUF_SIZE 16384
+
+static bool aspeed_smc_check_reads(struct aspeed_smc_chip *chip,
+				  const u8 *golden_buf, u8 *test_buf)
+{
+	int i;
+
+	for (i = 0; i < 10; i++) {
+		aspeed_smc_read_from_ahb(test_buf, chip->ahb_base,
+					 CALIBRATE_BUF_SIZE);
+		if (memcmp(test_buf, golden_buf, CALIBRATE_BUF_SIZE) != 0)
+			return false;
+	}
+	return true;
+}
+
+static int aspeed_smc_calibrate_reads(struct aspeed_smc_chip *chip, u32 hdiv,
+				      const u8 *golden_buf, u8 *test_buf)
+{
+	struct aspeed_smc_controller *controller = chip->controller;
+	const struct aspeed_smc_info *info = controller->info;
+	int i;
+	int good_pass = -1, pass_count = 0;
+	u32 shift = (hdiv - 1) << 2;
+	u32 mask = ~(0xfu << shift);
+	u32 fread_timing_val = 0;
+
+#define FREAD_TPASS(i)	(((i) / 2) | (((i) & 1) ? 0 : 8))
+
+	/* Try HCLK delay 0..5, each one with/without delay and look for a
+	 * good pair.
+	 */
+	for (i = 0; i < 12; i++) {
+		bool pass;
+
+		fread_timing_val &= mask;
+		fread_timing_val |= FREAD_TPASS(i) << shift;
+
+		writel(fread_timing_val, controller->regs + info->timing);
+		pass = aspeed_smc_check_reads(chip, golden_buf, test_buf);
+		dev_dbg(chip->nor.dev,
+			"  * [%08x] %d HCLK delay, %dns DI delay : %s",
+			fread_timing_val, i/2, (i & 1) ? 0 : 4,
+			pass ? "PASS" : "FAIL");
+		if (pass) {
+			pass_count++;
+			if (pass_count == 3) {
+				good_pass = i - 1;
+				break;
+			}
+		} else
+			pass_count = 0;
+	}
+
+	/* No good setting for this frequency */
+	if (good_pass < 0)
+		return -1;
+
+	/* We have at least one pass of margin, let's use first pass */
+	fread_timing_val &= mask;
+	fread_timing_val |= FREAD_TPASS(good_pass) << shift;
+	writel(fread_timing_val, controller->regs + info->timing);
+	dev_dbg(chip->nor.dev, " * -> good is pass %d [0x%08x]",
+		good_pass, fread_timing_val);
+	return 0;
+}
+
+static bool aspeed_smc_check_calib_data(const u8 *test_buf, u32 size)
+{
+	const u32 *tb32 = (const u32 *) test_buf;
+	u32 i, cnt = 0;
+
+	/* We check if we have enough words that are neither all 0
+	 * nor all 1's so the calibration can be considered valid.
+	 *
+	 * I use an arbitrary threshold for now of 64
+	 */
+	size >>= 2;
+	for (i = 0; i < size; i++) {
+		if (tb32[i] != 0 && tb32[i] != 0xffffffff)
+			cnt++;
+	}
+	return cnt >= 64;
+}
+
+static const uint32_t aspeed_smc_hclk_divs[] = {
+	0xf, /* HCLK */
+	0x7, /* HCLK/2 */
+	0xe, /* HCLK/3 */
+	0x6, /* HCLK/4 */
+	0xd, /* HCLK/5 */
+};
+#define ASPEED_SMC_HCLK_DIV(i) (aspeed_smc_hclk_divs[(i) - 1] << 8)
+
+static int aspeed_smc_optimize_reads(struct aspeed_smc_chip *chip,
+				     u32 max_freq)
+{
+	u8 *golden_buf, *test_buf;
+	int i, rc, best_div = -1;
+	u32 save_read_val = chip->ctl_val[smc_read];
+	u32 ahb_freq = clk_get_rate(chip->controller->ahb_clk);
+
+	dev_dbg(chip->nor.dev, "AHB frequency: %d MHz", ahb_freq / 1000000);
+
+	test_buf = kmalloc(CALIBRATE_BUF_SIZE * 2, GFP_KERNEL);
+	golden_buf = test_buf + CALIBRATE_BUF_SIZE;
+
+	/* We start with the dumbest setting (keep 4Byte bit) and read
+	 * some data
+	 */
+	chip->ctl_val[smc_read] = (chip->ctl_val[smc_read] & 0x2000) |
+		(0x00 << 28) | /* Single bit */
+		(0x00 << 24) | /* CE# max */
+		(0x03 << 16) | /* use normal reads */
+		(0x00 <<  8) | /* HCLK/16 */
+		(0x00 <<  6) | /* no dummy cycle */
+		(0x00);        /* normal read */
+
+	writel(chip->ctl_val[smc_read], chip->ctl);
+
+	aspeed_smc_read_from_ahb(golden_buf, chip->ahb_base,
+				 CALIBRATE_BUF_SIZE);
+
+	/* Establish our read mode with freq field set to 0 (HCLK/16) */
+	chip->ctl_val[smc_read] = save_read_val & 0xfffff0ff;
+
+	/* Check if calibration data is suitable */
+	if (!aspeed_smc_check_calib_data(golden_buf, CALIBRATE_BUF_SIZE)) {
+		dev_info(chip->nor.dev,
+			 "Calibration area too uniform, using low speed");
+		writel(chip->ctl_val[smc_read], chip->ctl);
+		kfree(test_buf);
+		return 0;
+	}
+
+	/* Now we iterate the HCLK dividers until we find our breaking point */
+	for (i = ARRAY_SIZE(aspeed_smc_hclk_divs); i > 0; i--) {
+		u32 tv, freq;
+
+		/* Compare timing to max */
+		freq = ahb_freq / i;
+		if (freq >= max_freq)
+			continue;
+
+		/* Set the timing */
+		tv = chip->ctl_val[smc_read] | ASPEED_SMC_HCLK_DIV(i);
+		writel(tv, chip->ctl);
+		dev_dbg(chip->nor.dev, "Trying HCLK/%d...", i);
+		rc = aspeed_smc_calibrate_reads(chip, i, golden_buf, test_buf);
+		if (rc == 0)
+			best_div = i;
+	}
+	kfree(test_buf);
+
+	/* Nothing found ? */
+	if (best_div < 0)
+		dev_warn(chip->nor.dev, "No good frequency, using dumb slow");
+	else {
+		dev_dbg(chip->nor.dev, "Found good read timings at HCLK/%d",
+			best_div);
+		chip->ctl_val[smc_read] |= ASPEED_SMC_HCLK_DIV(best_div);
+	}
+
+	writel(chip->ctl_val[smc_read], chip->ctl);
+	return 0;
+}
+
 static int aspeed_smc_chip_setup_finish(struct aspeed_smc_chip *chip)
 {
 	struct aspeed_smc_controller *controller = chip->controller;
@@ -918,6 +1097,12 @@ static int aspeed_smc_chip_setup_finish(struct aspeed_smc_chip *chip)
 
 	dev_dbg(controller->dev, "read control register: %08x\n",
 		chip->ctl_val[smc_read]);
+
+	/*
+	 * TODO: get max freq from chip
+	 */
+	if (info->optimize_reads)
+		info->optimize_reads(chip, 104000000);
 	return 0;
 }
 
-- 
2.7.4



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