diff options
Diffstat (limited to 'target/linux/ar71xx/patches-3.8/200-spi-ath79-add-delay-between-SCK-changes.patch')
| -rw-r--r-- | target/linux/ar71xx/patches-3.8/200-spi-ath79-add-delay-between-SCK-changes.patch | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/target/linux/ar71xx/patches-3.8/200-spi-ath79-add-delay-between-SCK-changes.patch b/target/linux/ar71xx/patches-3.8/200-spi-ath79-add-delay-between-SCK-changes.patch new file mode 100644 index 0000000000..7db744acf6 --- /dev/null +++ b/target/linux/ar71xx/patches-3.8/200-spi-ath79-add-delay-between-SCK-changes.patch @@ -0,0 +1,122 @@ +From cbb3ade4765bc715b5c2eae4a7b6eaf3ff7ad958 Mon Sep 17 00:00:00 2001 +From: Gabor Juhos <juhosg@openwrt.org> +Date: Wed, 11 Jan 2012 20:06:35 +0100 +Subject: [PATCH 28/34] spi/ath79: add delay between SCK changes + +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). Add 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> +--- + drivers/spi/spi-ath79.c | 44 +++++++++++++++++++++++++++++++++++++++++++- + 1 files changed, 43 insertions(+), 1 deletions(-) + +--- 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); |