From b0209b39951868069710c1e39ca14add9fa77ada Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Tue, 28 Feb 2012 00:39:39 +0100 Subject: i2c: export bit-banging algo functions i915 has a hw i2c controller (gmbus) but for a bunch of stupid reasons we need to be able to fall back to the bit-banging algo on gpio pins. The current code sets up a 2nd i2c controller for the same i2c bus using the bit-banging algo. This has a bunch of issues, the major one being that userspace can directly access this fallback i2c adaptor behind the drivers back. But we need to frob a few registers before and after using fallback gpio bit-banging, so this horribly fails. The new plan is to only set up one i2c adaptor and transparently fall back to bit-banging by directly calling the xfer function of the bit- banging algo in the i2c core. To make that possible, export the 2 i2c algo functions. v2: As suggested by Jean Delvare, simply export the i2c_bit_algo vtable instead of the individual functions. Acked-by: Jean Delvare Signed-off-by: Daniel Vetter --- drivers/i2c/algos/i2c-algo-bit.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/i2c/algos/i2c-algo-bit.c') diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index 525c7345fa0b..ad0459c4c1cf 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -610,10 +610,11 @@ static u32 bit_func(struct i2c_adapter *adap) /* -----exported algorithm data: ------------------------------------- */ -static const struct i2c_algorithm i2c_bit_algo = { +const struct i2c_algorithm i2c_bit_algo = { .master_xfer = bit_xfer, .functionality = bit_func, }; +EXPORT_SYMBOL(i2c_bit_algo); /* * registering functions to load algorithms at runtime -- cgit v1.2.3 From 8ee161ce5e0cfc689eb677f227a6248191165fac Mon Sep 17 00:00:00 2001 From: Ville Syrjala Date: Thu, 15 Mar 2012 18:11:05 +0100 Subject: i2c-algo-bit: Fix spurious SCL timeouts under heavy load When the system is under heavy load, there can be a significant delay between the getscl() and time_after() calls inside sclhi(). That delay may cause the time_after() check to trigger after SCL has gone high, causing sclhi() to return -ETIMEDOUT. To fix the problem, double check that SCL is still low after the timeout has been reached, before deciding to return -ETIMEDOUT. Signed-off-by: Ville Syrjala Cc: stable@vger.kernel.org Signed-off-by: Jean Delvare --- drivers/i2c/algos/i2c-algo-bit.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'drivers/i2c/algos/i2c-algo-bit.c') diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index 525c7345fa0b..24f94f4ae395 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -103,8 +103,14 @@ static int sclhi(struct i2c_algo_bit_data *adap) * chips may hold it low ("clock stretching") while they * are processing data internally. */ - if (time_after(jiffies, start + adap->timeout)) + if (time_after(jiffies, start + adap->timeout)) { + /* Test one last time, as we may have been preempted + * between last check and timeout test. + */ + if (getscl(adap)) + break; return -ETIMEDOUT; + } cond_resched(); } #ifdef DEBUG -- cgit v1.2.3 From 5694f8a888f8f69a562e4cf939eed81ca7a5ecf2 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Mon, 26 Mar 2012 21:47:19 +0200 Subject: i2c: Update the FSF address Signed-off-by: Jean Delvare --- drivers/i2c/algos/i2c-algo-bit.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/i2c/algos/i2c-algo-bit.c') diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index acba1c686c65..69902c8e3b1e 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -15,7 +15,8 @@ You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software - Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, + MA 02110-1301 USA. * ------------------------------------------------------------------------- */ /* With some changes from Frodo Looijaard , Kyösti Mälkki -- cgit v1.2.3 From 41101a33026c215a09e5d3549aedfcdae9105515 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Mon, 26 Mar 2012 21:47:19 +0200 Subject: i2c-algo-bit: Don't resched on clock stretching Clock stretching is not supposed to last long, so asking to be rescheduled while waiting for the clock line to be released by a slave makes little sense. Odds are that the clock line will long have been released when we run again, so we will have lost time and may even get an SMBus timeout because of this. So just busy-wait in that case. This also participates in the effort to make i2c-algo-bit usable in contexts that can't sleep. Signed-off-by: Jean Delvare Cc: Ben Skeggs --- drivers/i2c/algos/i2c-algo-bit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/i2c/algos/i2c-algo-bit.c') diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c index 69902c8e3b1e..7f0b83219744 100644 --- a/drivers/i2c/algos/i2c-algo-bit.c +++ b/drivers/i2c/algos/i2c-algo-bit.c @@ -112,7 +112,7 @@ static int sclhi(struct i2c_algo_bit_data *adap) break; return -ETIMEDOUT; } - cond_resched(); + cpu_relax(); } #ifdef DEBUG if (jiffies != start && i2c_debug >= 3) -- cgit v1.2.3