You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
127 lines
3.3 KiB
Diff
127 lines
3.3 KiB
Diff
From 486c150478777ef53cfef6f0d46840b9406b0612 Mon Sep 17 00:00:00 2001
|
|
From: Gabor Juhos <juhosg@openwrt.org>
|
|
Date: Thu, 27 Dec 2012 10:42:24 +0100
|
|
Subject: [PATCH] spi/ath79: add delay between SCK changes
|
|
|
|
commit 440114fdb13cbc53ea734bcc05b86bcf5b1e430c upstream.
|
|
|
|
The driver uses the "as fast as it can" approach
|
|
to drive the SCK signal. However this does not
|
|
work with certain low speed SPI chips (e.g. the
|
|
PCF2123 RTC chip).
|
|
|
|
The patch adds per-bit slowdowns in order to be
|
|
able to use the driver with such chips as well.
|
|
|
|
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
|
|
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
|
|
---
|
|
drivers/spi/spi-ath79.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
|
|
1 file changed, 43 insertions(+), 1 deletion(-)
|
|
|
|
--- a/drivers/spi/spi-ath79.c
|
|
+++ b/drivers/spi/spi-ath79.c
|
|
@@ -24,17 +24,24 @@
|
|
#include <linux/spi/spi_bitbang.h>
|
|
#include <linux/bitops.h>
|
|
#include <linux/gpio.h>
|
|
+#include <linux/clk.h>
|
|
+#include <linux/err.h>
|
|
|
|
#include <asm/mach-ath79/ar71xx_regs.h>
|
|
#include <asm/mach-ath79/ath79_spi_platform.h>
|
|
|
|
#define DRV_NAME "ath79-spi"
|
|
|
|
+#define ATH79_SPI_RRW_DELAY_FACTOR 12000
|
|
+#define MHZ (1000 * 1000)
|
|
+
|
|
struct ath79_spi {
|
|
struct spi_bitbang bitbang;
|
|
u32 ioc_base;
|
|
u32 reg_ctrl;
|
|
void __iomem *base;
|
|
+ struct clk *clk;
|
|
+ unsigned rrw_delay;
|
|
};
|
|
|
|
static inline u32 ath79_spi_rr(struct ath79_spi *sp, unsigned reg)
|
|
@@ -52,6 +59,12 @@ static inline struct ath79_spi *ath79_sp
|
|
return spi_master_get_devdata(spi->master);
|
|
}
|
|
|
|
+static inline void ath79_spi_delay(struct ath79_spi *sp, unsigned nsecs)
|
|
+{
|
|
+ if (nsecs > sp->rrw_delay)
|
|
+ ndelay(nsecs - sp->rrw_delay);
|
|
+}
|
|
+
|
|
static void ath79_spi_chipselect(struct spi_device *spi, int is_active)
|
|
{
|
|
struct ath79_spi *sp = ath79_spidev_to_sp(spi);
|
|
@@ -184,7 +197,9 @@ static u32 ath79_spi_txrx_mode0(struct s
|
|
|
|
/* setup MSB (to slave) on trailing edge */
|
|
ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out);
|
|
+ ath79_spi_delay(sp, nsecs);
|
|
ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out | AR71XX_SPI_IOC_CLK);
|
|
+ ath79_spi_delay(sp, nsecs);
|
|
|
|
word <<= 1;
|
|
}
|
|
@@ -198,6 +213,7 @@ static int ath79_spi_probe(struct platfo
|
|
struct ath79_spi *sp;
|
|
struct ath79_spi_platform_data *pdata;
|
|
struct resource *r;
|
|
+ unsigned long rate;
|
|
int ret;
|
|
|
|
master = spi_alloc_master(&pdev->dev, sizeof(*sp));
|
|
@@ -236,12 +252,36 @@ static int ath79_spi_probe(struct platfo
|
|
goto err_put_master;
|
|
}
|
|
|
|
+ sp->clk = clk_get(&pdev->dev, "ahb");
|
|
+ if (IS_ERR(sp->clk)) {
|
|
+ ret = PTR_ERR(sp->clk);
|
|
+ goto err_unmap;
|
|
+ }
|
|
+
|
|
+ ret = clk_enable(sp->clk);
|
|
+ if (ret)
|
|
+ goto err_clk_put;
|
|
+
|
|
+ rate = DIV_ROUND_UP(clk_get_rate(sp->clk), MHZ);
|
|
+ if (!rate) {
|
|
+ ret = -EINVAL;
|
|
+ goto err_clk_disable;
|
|
+ }
|
|
+
|
|
+ sp->rrw_delay = ATH79_SPI_RRW_DELAY_FACTOR / rate;
|
|
+ dev_dbg(&pdev->dev, "register read/write delay is %u nsecs\n",
|
|
+ sp->rrw_delay);
|
|
+
|
|
ret = spi_bitbang_start(&sp->bitbang);
|
|
if (ret)
|
|
- goto err_unmap;
|
|
+ goto err_clk_disable;
|
|
|
|
return 0;
|
|
|
|
+err_clk_disable:
|
|
+ clk_disable(sp->clk);
|
|
+err_clk_put:
|
|
+ clk_put(sp->clk);
|
|
err_unmap:
|
|
iounmap(sp->base);
|
|
err_put_master:
|
|
@@ -256,6 +296,8 @@ static int ath79_spi_remove(struct platf
|
|
struct ath79_spi *sp = platform_get_drvdata(pdev);
|
|
|
|
spi_bitbang_stop(&sp->bitbang);
|
|
+ clk_disable(sp->clk);
|
|
+ clk_put(sp->clk);
|
|
iounmap(sp->base);
|
|
platform_set_drvdata(pdev, NULL);
|
|
spi_master_put(sp->bitbang.master);
|