Message ID | 4A0BD1DB.4090305@doredevelopment.dk (mailing list archive) |
---|---|
State | Superseded, archived |
Delegated to: | Kumar Gala |
Headers | show |
On Thu, May 14, 2009 at 10:10:03AM +0200, Esben Haabendal wrote: > This fixes MAL (arbitration lost) bug caused by illegal use of > RSTA (repeated START) after STOP condition generated after last byte > of reads. > Could you elaborate a bit, please? Like an example when the original bug occured (so I could reproduce easily) and how this patch actually solves the problem. > Signed-off-by: Esben Haabendal <eha@doredevelopment.dk> > --- > drivers/i2c/busses/i2c-mpc.c | 9 +++++++-- > 1 files changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c > index 4af5c09..9fe05d9 100644 > --- a/drivers/i2c/busses/i2c-mpc.c > +++ b/drivers/i2c/busses/i2c-mpc.c > @@ -456,17 +456,22 @@ static int mpc_xfer(struct i2c_adapter *adap, > struct i2c_msg *msgs, int num) > } > > for (i = 0; ret >= 0 && i < num; i++) { > + int restart = i; > pmsg = &msgs[i]; > dev_dbg(i2c->dev, > "Doing %s %d bytes to 0x%02x - %d of %d messages\n", > pmsg->flags & I2C_M_RD ? "read" : "write", > pmsg->len, pmsg->addr, i + 1, num); > + if (i > 0 && ((pmsg-1)->flags & I2C_M_RD)) CodingStyle: Spaces around '-' > + restart = 0; > if (pmsg->flags & I2C_M_RD) > ret = > - mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, i); > + mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, > + restart); > else > ret = > - mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, i); > + mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, > + restart); > } > mpc_i2c_stop(i2c); > return (ret < 0) ? ret : num; > -- > 1.6.0.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-i2c" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
Wolfram Sang wrote: > On Thu, May 14, 2009 at 10:10:03AM +0200, Esben Haabendal wrote: > >> This fixes MAL (arbitration lost) bug caused by illegal use of >> RSTA (repeated START) after STOP condition generated after last byte >> of reads. >> >> > > Could you elaborate a bit, please? Like an example when the original bug > occured (so I could reproduce easily) and how this patch actually solves > the problem. > Sure. I used the following code to initialize a CS4265 chip: (simplified here for the example) static int i2c_init_chip(void) { int err=0; char write_dac_control_1[] = { 0x03, chip->regs.dac_control_1 }; char seek_chip_id[] = { 0x01 }; char write_power_control[] = { 0x02, chip->regs.power_control }; struct i2c_msg cs4265_init_cmds[] = { { chip->i2c_addr, 0, 2, write_dac_control_1 }, { chip->i2c_addr, 0, 1, seek_chip_id }, { chip->i2c_addr, I2C_M_RD, 1, ®s.chip_id }, { chip->i2c_addr, 0, 2, write_power_control }, }; err = i2c_transfer(i2c, cs4265_init_cmds, sizeof(cs4265_init_cmds)/sizeof(*cs4265_init_cmds)); if (err < 0) { printk(KERN_ERR "i2c_transfer failed: %d\n", err); return err; } return 0; } I have added some additional debug output and traces something like this: [ 36.114297] writeccr 80 [MEN] [ 36.114324] mpc_xfer: 2 bytes to 4f:W - 1 of 5 messages [ 36.120176] next 1 bytes to 4f:W [ 36.124159] mpc_write addr=4f len=2 [ 36.128044] writeccr 80 [MEN] [ 36.128062] writeccr f0 [MEN MIEN MSTA MTX] -> START [ 36.128219] I2C: SR=a2 [ 36.131528] I2C: SR=a6 [ 36.134406] I2C: SR=a2 [ 36.137165] mpc_xfer: 1 bytes to 4f:W - 2 of 5 messages [ 36.142802] next 1 bytes to 4f:R [ 36.146699] mpc_write addr=4f len=1 [ 36.150583] writeccr f4 [MEN MIEN MSTA MTX RSTA] -> repeated START [ 36.150758] I2C: SR=a2 [ 36.153851] I2C: SR=a6 [ 36.156236] mpc_xfer: 1 bytes to 4f:R - 3 of 5 messages [ 36.162081] next 2 bytes to 4f:W [ 36.166062] mpc_read addr=4f len=1 [ 36.169858] writeccr f4 [MEN MIEN MSTA MTX RSTA] -> repeated START [ 36.170031] I2C: SR=a6 [ 36.172993] writeccr e8 [MEN MIEN MSTA TXAK] -> receive & no ACK [ 36.173143] I2C: SR=a7 [ 36.175511] writeccr c8 [MEN MIEN TXAK] -> STOP [ 36.175529] mpc_xfer: 2 bytes to 4f:W - 4 of 5 messages [ 36.181804] next 2 bytes to 4f:W [ 36.185788] mpc_write addr=4f len=2 [ 36.189672] writeccr f4 [MEN MIEN MSTA MTX RSTA] -> repeated START [ 36.189704] I2C: SR=b7 [ 36.192072] I2C: MAL [ 36.195075] i2c_wait(address) error: -5 [ 36.199311] writeccr 80 The problem is that after the STOP condition, the following i2c_msg will be attempted with a repeated START, which according to specification will cause a MAL, which also happens. My MPC8360ERM reads: "Attempting a repeated START at the wrong time (or if the bus is owned by another master), results in loss of arbitration." Which I know read as it that we must own the I2C bus when using RSTA. > > >> Signed-off-by: Esben Haabendal <eha@doredevelopment.dk> >> --- >> drivers/i2c/busses/i2c-mpc.c | 9 +++++++-- >> 1 files changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c >> index 4af5c09..9fe05d9 100644 >> --- a/drivers/i2c/busses/i2c-mpc.c >> +++ b/drivers/i2c/busses/i2c-mpc.c >> @@ -456,17 +456,22 @@ static int mpc_xfer(struct i2c_adapter *adap, >> struct i2c_msg *msgs, int num) >> } >> >> for (i = 0; ret >= 0 && i < num; i++) { >> + int restart = i; >> pmsg = &msgs[i]; >> dev_dbg(i2c->dev, >> "Doing %s %d bytes to 0x%02x - %d of %d messages\n", >> pmsg->flags & I2C_M_RD ? "read" : "write", >> pmsg->len, pmsg->addr, i + 1, num); >> + if (i > 0 && ((pmsg-1)->flags & I2C_M_RD)) >> > > CodingStyle: Spaces around '-' > Ok. > >> + restart = 0; >> if (pmsg->flags & I2C_M_RD) >> ret = >> - mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, i); >> + mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, >> + restart); >> else >> ret = >> - mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, i); >> + mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, >> + restart); >> } >> mpc_i2c_stop(i2c); >> return (ret < 0) ? ret : num; >> -- >> 1.6.0.4 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-i2c" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > >
> > Wolfram Sang wrote: > > On Thu, May 14, 2009 at 10:10:03AM +0200, Esben Haabendal wrote: > > > >> This fixes MAL (arbitration lost) bug caused by illegal use of > >> RSTA (repeated START) after STOP condition generated after last byte > >> of reads. > >> > >> > > > > Could you elaborate a bit, please? Like an example when the original bug > > occured (so I could reproduce easily) and how this patch actually solves > > the problem. > > > Sure. I used the following code to initialize a CS4265 chip: > (simplified here for the example) > > static int > i2c_init_chip(void) > { > int err=0; > char write_dac_control_1[] = { 0x03, chip->regs.dac_control_1 }; > char seek_chip_id[] = { 0x01 }; > char write_power_control[] = { 0x02, chip->regs.power_control }; > struct i2c_msg cs4265_init_cmds[] = { > { chip->i2c_addr, 0, 2, write_dac_control_1 }, > { chip->i2c_addr, 0, 1, seek_chip_id }, > { chip->i2c_addr, I2C_M_RD, 1, ®s.chip_id }, > { chip->i2c_addr, 0, 2, write_power_control }, > }; > > err = i2c_transfer(i2c, cs4265_init_cmds, > sizeof(cs4265_init_cmds)/sizeof(*cs4265_init_cmds)); > if (err < 0) { > printk(KERN_ERR "i2c_transfer failed: %d\n", err); > return err; > } > > return 0; > } > > I have added some additional debug output and traces something like this: > > [ 36.114297] writeccr 80 [MEN] > [ 36.114324] mpc_xfer: 2 bytes to 4f:W - 1 of 5 messages > [ 36.120176] next 1 bytes to 4f:W > [ 36.124159] mpc_write addr=4f len=2 > [ 36.128044] writeccr 80 [MEN] > [ 36.128062] writeccr f0 [MEN MIEN MSTA MTX] -> START > [ 36.128219] I2C: SR=a2 > [ 36.131528] I2C: SR=a6 > [ 36.134406] I2C: SR=a2 > > [ 36.137165] mpc_xfer: 1 bytes to 4f:W - 2 of 5 messages > [ 36.142802] next 1 bytes to 4f:R > [ 36.146699] mpc_write addr=4f len=1 > [ 36.150583] writeccr f4 [MEN MIEN MSTA MTX RSTA] -> repeated START > [ 36.150758] I2C: SR=a2 > [ 36.153851] I2C: SR=a6 > > [ 36.156236] mpc_xfer: 1 bytes to 4f:R - 3 of 5 messages > [ 36.162081] next 2 bytes to 4f:W > [ 36.166062] mpc_read addr=4f len=1 > [ 36.169858] writeccr f4 [MEN MIEN MSTA MTX RSTA] -> repeated START > [ 36.170031] I2C: SR=a6 > [ 36.172993] writeccr e8 [MEN MIEN MSTA TXAK] -> receive & no ACK > [ 36.173143] I2C: SR=a7 > [ 36.175511] writeccr c8 [MEN MIEN TXAK] -> STOP > > [ 36.175529] mpc_xfer: 2 bytes to 4f:W - 4 of 5 messages > [ 36.181804] next 2 bytes to 4f:W > [ 36.185788] mpc_write addr=4f len=2 > [ 36.189672] writeccr f4 [MEN MIEN MSTA MTX RSTA] -> repeated START > [ 36.189704] I2C: SR=b7 > [ 36.192072] I2C: MAL > [ 36.195075] i2c_wait(address) error: -5 > [ 36.199311] writeccr 80 > > The problem is that after the STOP condition, the following i2c_msg will be > attempted with a repeated START, which according to specification will > cause a MAL, which also happens. My MPC8360ERM reads: > > "Attempting a repeated START at the wrong time (or if the bus is owned > by another master), results in loss of arbitration." > > Which I know read as it that we must own the I2C bus when using RSTA. I agree with the theory, but isn't the problem here that STOP is performed in the middle of this transaction? Remove the STOP and RSTA will work I think. Jocke
diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c index 4af5c09..9fe05d9 100644 --- a/drivers/i2c/busses/i2c-mpc.c +++ b/drivers/i2c/busses/i2c-mpc.c @@ -456,17 +456,22 @@ static int mpc_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) } for (i = 0; ret >= 0 && i < num; i++) { + int restart = i; pmsg = &msgs[i]; dev_dbg(i2c->dev, "Doing %s %d bytes to 0x%02x - %d of %d messages\n", pmsg->flags & I2C_M_RD ? "read" : "write", pmsg->len, pmsg->addr, i + 1, num); + if (i > 0 && ((pmsg-1)->flags & I2C_M_RD)) + restart = 0; if (pmsg->flags & I2C_M_RD) ret = - mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, i); + mpc_read(i2c, pmsg->addr, pmsg->buf, pmsg->len, + restart); else ret = - mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, i); + mpc_write(i2c, pmsg->addr, pmsg->buf, pmsg->len, + restart); } mpc_i2c_stop(i2c);
This fixes MAL (arbitration lost) bug caused by illegal use of RSTA (repeated START) after STOP condition generated after last byte of reads. Signed-off-by: Esben Haabendal <eha@doredevelopment.dk> --- drivers/i2c/busses/i2c-mpc.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) return (ret < 0) ? ret : num;