lkml.org 
[lkml]   [2020]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2] mtd: mtk-quadspi: add support for DMA reading
Date
PIO reading mode on this controller is pretty inefficient
(one cmd+addr+dummy sequence reads only one byte)
This patch adds support for reading using DMA mode which increases
reading speed from 1MB/s to 4MB/s

DMA busy checking is implemented with readl_poll_timeout because
I don't have access to IRQ-related docs. The speed increment comes
from those saved cmd+addr+dummy clocks.

This controller requires that DMA source/destination address and
reading length should be 16-byte aligned. We use a bounce buffer if
one of them is not aligned, read more than what we need, and copy
data from corresponding buffer offset.

Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
---

Changes since v1:
1. cast pointers to ulong instead of u32 to fix warnings on 64bit
platform
2. drop the other patch for reading with custom opcode. That'll
be a separated fix which is unrelated to this one.

drivers/mtd/spi-nor/mtk-quadspi.c | 99 +++++++++++++++++++++++++++++--
1 file changed, 95 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/spi-nor/mtk-quadspi.c b/drivers/mtd/spi-nor/mtk-quadspi.c
index b1691680d174..85101b84b516 100644
--- a/drivers/mtd/spi-nor/mtk-quadspi.c
+++ b/drivers/mtd/spi-nor/mtk-quadspi.c
@@ -7,6 +7,7 @@
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
+#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/iopoll.h>
@@ -17,6 +18,7 @@
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
+#include <linux/sched/task_stack.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
@@ -70,6 +72,10 @@
#define MTK_NOR_DELSEL2_REG 0xd0
#define MTK_NOR_DELSEL3_REG 0xd4
#define MTK_NOR_DELSEL4_REG 0xd8
+#define MTK_NOR_FDMA_CTL_REG 0x718
+#define MTK_NOR_FDMA_FADR_REG 0x71c
+#define MTK_NOR_FDMA_DADR_REG 0x720
+#define MTK_NOR_FDMA_END_DADR_REG 0x724

/* commands for mtk nor controller */
#define MTK_NOR_READ_CMD 0x0
@@ -88,6 +94,7 @@
#define MTK_NOR_DUAL_READ_EN 0x1
#define MTK_NOR_DUAL_DISABLE 0x0
#define MTK_NOR_FAST_READ 0x1
+#define MTK_NOR_DMA_TRIG 0x1

#define SFLASH_WRBUF_SIZE 128

@@ -97,7 +104,10 @@
#define MTK_NOR_MAX_SHIFT 7
/* nor controller 4-byte address mode enable bit */
#define MTK_NOR_4B_ADDR_EN BIT(4)
-
+/* DMA address has to be 16-byte aligned */
+#define MTK_NOR_DMA_ALIGN 16
+/* Limit bounce buffer size to 32KB */
+#define MTK_NOR_MAX_BBUF_READ (32 * 1024)
/* Helpers for accessing the program data / shift data registers */
#define MTK_NOR_PRG_REG(n) (MTK_NOR_PRGDATA0_REG + 4 * (n))
#define MTK_NOR_SHREG(n) (MTK_NOR_SHREG0_REG + 4 * (n))
@@ -260,13 +270,12 @@ static void mtk_nor_set_addr(struct mtk_nor *mtk_nor, u32 addr)
writeb(addr & 0xff, mtk_nor->base + MTK_NOR_RADR3_REG);
}

-static ssize_t mtk_nor_read(struct spi_nor *nor, loff_t from, size_t length,
- u_char *buffer)
+static ssize_t mtk_nor_read_pio(struct mtk_nor *mtk_nor, loff_t from,
+ size_t length, u_char *buffer)
{
int i, ret;
int addr = (int)from;
u8 *buf = (u8 *)buffer;
- struct mtk_nor *mtk_nor = nor->priv;

/* set mode for fast read mode ,dual mode or quad mode */
mtk_nor_set_read_mode(mtk_nor);
@@ -281,6 +290,88 @@ static ssize_t mtk_nor_read(struct spi_nor *nor, loff_t from, size_t length,
return length;
}

+static int mtk_nor_dma_exec(struct mtk_nor *mtk_nor)
+{
+ int reg;
+
+ reg = readl(mtk_nor->base + MTK_NOR_FDMA_CTL_REG);
+ writel(reg | MTK_NOR_DMA_TRIG, mtk_nor->base + MTK_NOR_FDMA_CTL_REG);
+ return readl_poll_timeout(mtk_nor->base + MTK_NOR_FDMA_CTL_REG, reg,
+ !(reg & MTK_NOR_DMA_TRIG), 20, 10000);
+}
+
+static ssize_t mtk_nor_read_dma(struct mtk_nor *mtk_nor, loff_t from,
+ size_t length, u_char *buffer)
+{
+ ssize_t ret;
+ ssize_t read_length = length & ~(MTK_NOR_DMA_ALIGN - 1);
+ dma_addr_t dma_addr;
+
+ mtk_nor_set_read_mode(mtk_nor);
+ mtk_nor_set_addr_width(mtk_nor);
+
+ dma_addr = dma_map_single(mtk_nor->dev, buffer, read_length,
+ DMA_FROM_DEVICE);
+ if (dma_mapping_error(mtk_nor->dev, dma_addr)) {
+ dev_err(mtk_nor->dev, "failed to map dma buffer.");
+ return -EINVAL;
+ }
+
+ writel(from, mtk_nor->base + MTK_NOR_FDMA_FADR_REG);
+ writel(dma_addr, mtk_nor->base + MTK_NOR_FDMA_DADR_REG);
+ writel((u32)dma_addr + read_length,
+ mtk_nor->base + MTK_NOR_FDMA_END_DADR_REG);
+ ret = mtk_nor_dma_exec(mtk_nor);
+ dma_unmap_single(mtk_nor->dev, dma_addr, read_length, DMA_FROM_DEVICE);
+ if (!ret)
+ ret = read_length;
+ return ret;
+}
+
+static ssize_t mtk_nor_read_dma_bounce(struct mtk_nor *mtk_nor, loff_t from,
+ size_t length, u_char *buffer)
+{
+ ssize_t nor_unaligned_len = from % MTK_NOR_DMA_ALIGN;
+ loff_t read_from = from & ~(MTK_NOR_DMA_ALIGN - 1);
+ ssize_t read_len;
+ u_char *buf;
+ u_char *bouncebuf;
+ size_t mem_unaligned_len;
+
+ if (length > MTK_NOR_MAX_BBUF_READ)
+ length = MTK_NOR_MAX_BBUF_READ;
+ read_len = length + nor_unaligned_len + MTK_NOR_DMA_ALIGN;
+
+ buf = kmalloc(read_len + MTK_NOR_DMA_ALIGN, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ mem_unaligned_len = (ulong)buf % MTK_NOR_DMA_ALIGN;
+ bouncebuf = (buf + MTK_NOR_DMA_ALIGN) - mem_unaligned_len;
+
+ read_len = mtk_nor_read_dma(mtk_nor, read_from, read_len, bouncebuf);
+ if (read_len > 0)
+ memcpy(buffer, bouncebuf + nor_unaligned_len, length);
+
+ kfree(buf);
+ return length;
+}
+
+static ssize_t mtk_nor_read(struct spi_nor *nor, loff_t from, size_t length,
+ u_char *buffer)
+{
+ struct mtk_nor *mtk_nor = nor->priv;
+
+ if (length < MTK_NOR_DMA_ALIGN)
+ return mtk_nor_read_pio(mtk_nor, from, length, buffer);
+
+ if (object_is_on_stack(buffer) || !virt_addr_valid(buffer) ||
+ (ulong)buffer % MTK_NOR_DMA_ALIGN || from % MTK_NOR_DMA_ALIGN)
+ return mtk_nor_read_dma_bounce(mtk_nor, from, length, buffer);
+
+ return mtk_nor_read_dma(mtk_nor, from, length, buffer);
+}
+
static int mtk_nor_write_single_byte(struct mtk_nor *mtk_nor,
int addr, int length, u8 *data)
{
--
2.24.1
\
 
 \ /
  Last update: 2020-02-08 09:41    [W:0.077 / U:3.388 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site