[3/4] mtd: spi-nor: aspeed: configure chip window on AHB bus

diff --git a/drivers/mtd/spi-nor/aspeed-smc.c b/drivers/mtd/spi-nor/aspeed-smc.c
index 183d950e621b..60c020482946 100644
--- a/drivers/mtd/spi-nor/aspeed-smc.c
+++ b/drivers/mtd/spi-nor/aspeed-smc.c
@@ -97,6 +97,7 @@  struct aspeed_smc_chip {
 	struct aspeed_smc_controller *controller;
 	void __iomem *ctl;			/* control register */
 	void __iomem *ahb_base;			/* base of chip window */
+	u32 ahb_window_size;			/* chip mapping window size */
 	u32 ctl_val[smc_max];			/* control settings */
 	enum aspeed_smc_flash_type type;	/* what type of flash */
 	struct spi_nor nor;
@@ -109,6 +110,7 @@  struct aspeed_smc_controller {
 	const struct aspeed_smc_info *info;	/* type info of controller */
 	void __iomem *regs;			/* controller registers */
 	void __iomem *ahb_base;			/* per-chip windows resource */
+	u32 ahb_window_size;			/* full mapping window size */
 
 	struct aspeed_smc_chip *chips[0];	/* pointers to attached chips */
 };
@@ -193,6 +195,10 @@  struct aspeed_smc_controller {
 #define SEGMENT_ADDR_REG0		0x30
 #define SEGMENT_ADDR_START(_r)		((((_r) >> 16) & 0xFF) << 23)
 #define SEGMENT_ADDR_END(_r)		((((_r) >> 24) & 0xFF) << 23)
+#define SEGMENT_ADDR_VALUE(start, end)					\
+	(((((start) >> 23) & 0xFF) << 16) | ((((end) >> 23) & 0xFF) << 24))
+#define SEGMENT_ADDR_REG(controller, cs)	\
+	((controller)->regs + SEGMENT_ADDR_REG0 + (cs) * 4)
 
 /*
  * In user mode all data bytes read or written to the chip decode address
@@ -446,8 +452,7 @@  static void __iomem *aspeed_smc_chip_base(struct aspeed_smc_chip *chip,
 	u32 reg;
 
 	if (controller->info->nce > 1) {
-		reg = readl(controller->regs + SEGMENT_ADDR_REG0 +
-			    chip->cs * 4);
+		reg = readl(SEGMENT_ADDR_REG(controller, chip->cs));
 
 		if (SEGMENT_ADDR_START(reg) >= SEGMENT_ADDR_END(reg))
 			return NULL;
@@ -458,6 +463,146 @@  static void __iomem *aspeed_smc_chip_base(struct aspeed_smc_chip *chip,
 	return controller->ahb_base + offset;
 }
 
+static u32 aspeed_smc_ahb_base_phy(struct aspeed_smc_controller *controller)
+{
+	u32 seg0_val = readl(SEGMENT_ADDR_REG(controller, 0));
+
+	return SEGMENT_ADDR_START(seg0_val);
+}
+
+static u32 chip_set_segment(struct aspeed_smc_chip *chip, u32 cs, u32 start,
+			    u32 size)
+{
+	struct aspeed_smc_controller *controller = chip->controller;
+	void __iomem *seg_reg;
+	u32 seg_oldval, seg_newval, ahb_base_phy, end;
+
+	ahb_base_phy = aspeed_smc_ahb_base_phy(controller);
+
+	seg_reg = SEGMENT_ADDR_REG(controller, cs);
+	seg_oldval = readl(seg_reg);
+
+	/*
+	 * If the chip size is not specified, use the default segment
+	 * size, but take into account the possible overlap with the
+	 * previous segment
+	 */
+	if (!size)
+		size = SEGMENT_ADDR_END(seg_oldval) - start;
+
+	/*
+	 * The segment cannot exceed the maximum window size of the
+	 * controller.
+	 */
+	if (start + size > ahb_base_phy + controller->ahb_window_size) {
+		size = ahb_base_phy + controller->ahb_window_size - start;
+		dev_warn(chip->nor.dev, "CE%d window resized to %dMB",
+			 cs, size >> 20);
+	}
+
+	end = start + size;
+	seg_newval = SEGMENT_ADDR_VALUE(start, end);
+	writel(seg_newval, seg_reg);
+
+	/*
+	 * Restore default value if something goes wrong. The chip
+	 * might have set some bogus value and we would loose access
+	 * to the chip.
+	 */
+	if (seg_newval != readl(seg_reg)) {
+		dev_err(chip->nor.dev, "CE%d window invalid", cs);
+		writel(seg_oldval, seg_reg);
+		start = SEGMENT_ADDR_START(seg_oldval);
+		end = SEGMENT_ADDR_END(seg_oldval);
+		size = end - start;
+	}
+
+	dev_info(chip->nor.dev, "CE%d window [ 0x%.8x - 0x%.8x ] %dMB",
+		 cs, start, end, size >> 20);
+
+	return size;
+}
+
+/*
+ * The segment register defines the mapping window on the AHB bus and
+ * it needs to be configured depending on the chip size. The segment
+ * register of the following CE also needs to be tuned in order to
+ * provide a contiguous window across multiple chips.
+ *
+ * This is expected to be called in increasing CE order
+ */
+static u32 aspeed_smc_chip_set_segment(struct aspeed_smc_chip *chip)
+{
+	struct aspeed_smc_controller *controller = chip->controller;
+	u32 ahb_base_phy, start;
+	u32 size = chip->nor.mtd.size;
+
+	/*
+	 * Each controller has a chip size limit for direct memory
+	 * access
+	 */
+	if (size > controller->info->maxsize)
+		size = controller->info->maxsize;
+
+	/*
+	 * The AST2400 SPI controller only handles one chip and does
+	 * not have segment registers. Let's use the chip size for the
+	 * AHB window.
+	 */
+	if (controller->info == &spi_2400_info)
+		goto out;
+
+	/*
+	 * The AST2500 SPI controller has a HW bug when the CE0 chip
+	 * size reaches 128MB. Enforce a size limit of 120MB to
+	 * prevent the controller from using bogus settings in the
+	 * segment register.
+	 */
+	if (chip->cs == 0 && controller->info == &spi_2500_info &&
+	    size == SZ_128M) {
+		size = 120 << 20;
+		dev_info(chip->nor.dev,
+			 "CE%d window resized to %dMB (AST2500 HW quirk)",
+			 chip->cs, size >> 20);
+	}
+
+	ahb_base_phy = aspeed_smc_ahb_base_phy(controller);
+
+	/*
+	 * As a start address for the current segment, use the default
+	 * start address if we are handling CE0 or use the previous
+	 * segment ending address
+	 */
+	if (chip->cs) {
+		u32 prev = readl(SEGMENT_ADDR_REG(controller, chip->cs - 1));
+
+		start = SEGMENT_ADDR_END(prev);
+	} else {
+		start = ahb_base_phy;
+	}
+
+	size = chip_set_segment(chip, chip->cs, start, size);
+
+	/* Update chip base address on the AHB bus */
+	chip->ahb_base = controller->ahb_base + (start - ahb_base_phy);
+
+	/*
+	 * Now, make sure the next segment does not overlap with the
+	 * current one we just configured, even if there is no
+	 * available chip. That could break access in Command Mode.
+	 */
+	if (chip->cs < controller->info->nce - 1)
+		chip_set_segment(chip, chip->cs + 1, start + size, 0);
+
+out:
+	if (size < chip->nor.mtd.size)
+		dev_warn(chip->nor.dev,
+			 "CE%d window too small for chip %dMB",
+			 chip->cs, (u32)chip->nor.mtd.size >> 20);
+
+	return size;
+}
+
 static void aspeed_smc_chip_enable_write(struct aspeed_smc_chip *chip)
 {
 	struct aspeed_smc_controller *controller = chip->controller;
@@ -531,7 +676,7 @@  static int aspeed_smc_chip_setup_init(struct aspeed_smc_chip *chip,
 	 */
 	chip->ahb_base = aspeed_smc_chip_base(chip, res);
 	if (!chip->ahb_base) {
-		dev_warn(chip->nor.dev, "CE segment window closed.\n");
+		dev_warn(chip->nor.dev, "CE%d window closed", chip->cs);
 		return -EINVAL;
 	}
 
@@ -578,6 +723,9 @@  static int aspeed_smc_chip_setup_finish(struct aspeed_smc_chip *chip)
 	if (chip->nor.addr_width == 4 && info->set_4b)
 		info->set_4b(chip);
 
+	/* This is for direct AHB access when using Command Mode. */
+	chip->ahb_window_size = aspeed_smc_chip_set_segment(chip);
+
 	/*
 	 * base mode has not been optimized yet. use it for writes.
 	 */
@@ -739,6 +887,8 @@  static int aspeed_smc_probe(struct platform_device *pdev)
 	if (IS_ERR(controller->ahb_base))
 		return PTR_ERR(controller->ahb_base);
 
+	controller->ahb_window_size = resource_size(res);
+
 	ret = aspeed_smc_setup_flash(controller, np, res);
 	if (ret)
 		dev_err(dev, "Aspeed SMC probe failed %d\n", ret);