* Tony Lindgren <tony@xxxxxxxxxxx> [080328 10:41]: > Hi all, > > This helps with the annoying I2C timeouts. Does anybody have an idea > why the twl4030 chip does not like doing multiple transfers in a row? > > To me the only difference seems to be that clocks are idled between > writing the twl4030 register and reading the register value. I'll push this today with a REVISIT comment added. Tony > From 25c4c8f449819cb6f40b59ed1a9b25ebcc7cd72e Mon Sep 17 00:00:00 2001 > From: Tony Lindgren <tony@xxxxxxxxxxx> > Date: Thu, 27 Mar 2008 19:05:30 +0200 > Subject: [PATCH] I2C: Fix twl4030 timeouts on omap3430 > > For some reason doing a twl4030 write-read cycle can hang the I2C bus > on omap3430. And doing the write and read separately in twl4030_i2c_read() > seems to fix the problem... > > Not intended for applying, just a temporary workaround. > > diff --git a/drivers/i2c/chips/twl4030-core.c b/drivers/i2c/chips/twl4030-core.c > index ded86e7..62868b0 100644 > --- a/drivers/i2c/chips/twl4030-core.c > +++ b/drivers/i2c/chips/twl4030-core.c > @@ -327,6 +327,7 @@ int twl4030_i2c_read(u8 mod_no, u8 * value, u8 reg, u8 num_bytes) > return -EPERM; > } > mutex_lock(&twl->xfer_lock); > + > /* [MSG1] fill the register address data */ > msg = &twl->xfer_msg[0]; > msg->addr = twl->address; > @@ -334,18 +335,25 @@ int twl4030_i2c_read(u8 mod_no, u8 * value, u8 reg, u8 num_bytes) > msg->flags = 0; /* Read the register value */ > val = twl4030_map[mod_no].base + reg; > msg->buf = &val; > + ret = i2c_transfer(twl->client.adapter, twl->xfer_msg, 1); > + if (ret < 0) > + goto out; > + > /* [MSG2] fill the data rx buffer */ > msg = &twl->xfer_msg[1]; > msg->addr = twl->address; > msg->flags = I2C_M_RD; /* Read the register value */ > msg->len = num_bytes; /* only n bytes */ > msg->buf = value; > - ret = i2c_transfer(twl->client.adapter, twl->xfer_msg, 2); > + ret = i2c_transfer(twl->client.adapter, twl->xfer_msg, 1); > + > +out: > mutex_unlock(&twl->xfer_lock); > > /* i2cTransfer returns num messages.translate it pls.. */ > if (ret >= 0) > ret = 0; > + > return ret; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
