diff options
| author | Alexander Shiyan <shc_work@mail.ru> | 2014-05-08 11:56:40 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-06-19 17:43:34 -0700 |
| commit | f80b2581a7068907076ca92c43866f36f446c039 (patch) | |
| tree | 8b98431b0debc428c33bfde35fe310a89fbd63b4 /drivers/w1 | |
| parent | b7ce0b5d03f303cba0fff3f9df17f400d4e7a2d8 (diff) | |
| download | lwn-f80b2581a7068907076ca92c43866f36f446c039.tar.gz lwn-f80b2581a7068907076ca92c43866f36f446c039.zip | |
w1: mxc_w1: Optimize mxc_w1_ds2_touch_bit()
According to the i.MX reference manual, the read/write bit operations
takes from 60 us to 120 us.
This patch optimizes mxc_w1_ds2_touch_bit() function to use proper
value for such delay. Nevertheless, a small margin for the timeout has
been added for the case if clock frequency is inaccurate.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/w1')
| -rw-r--r-- | drivers/w1/masters/mxc_w1.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/drivers/w1/masters/mxc_w1.c b/drivers/w1/masters/mxc_w1.c index 741d2bb400ae..da3d0f0ad63c 100644 --- a/drivers/w1/masters/mxc_w1.c +++ b/drivers/w1/masters/mxc_w1.c @@ -75,22 +75,25 @@ static u8 mxc_w1_ds2_reset_bus(void *data) */ static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit) { - struct mxc_w1_device *mdev = data; - void __iomem *ctrl_addr = mdev->regs + MXC_W1_CONTROL; - unsigned int timeout_cnt = 400; /* Takes max. 120us according to - * datasheet. - */ + struct mxc_w1_device *dev = data; + unsigned long timeout; + + writeb(MXC_W1_CONTROL_WR(bit), dev->regs + MXC_W1_CONTROL); + + /* Wait for read/write bit (60us, Max 120us), use 200us for sure */ + timeout = jiffies + usecs_to_jiffies(200); - writeb(MXC_W1_CONTROL_WR(bit), ctrl_addr); + udelay(60); - while (timeout_cnt--) { - if (!(readb(ctrl_addr) & MXC_W1_CONTROL_WR(bit))) - break; + do { + u8 ctrl = readb(dev->regs + MXC_W1_CONTROL); - udelay(1); - } + /* RDST bit is valid after the WR1/RD bit is self-cleared */ + if (!(ctrl & MXC_W1_CONTROL_WR(bit))) + return !!(ctrl & MXC_W1_CONTROL_RDST); + } while (time_is_after_jiffies(timeout)); - return !!(readb(ctrl_addr) & MXC_W1_CONTROL_RDST); + return 0; } static int mxc_w1_probe(struct platform_device *pdev) |