Re: [PATCH 5/5] i2c: octeon,thunderx: Limit register access retries

2016-09-22 Thread Jan Glauber 
On Wed, Sep 21, 2016 at 11:03:35PM +0200, Wolfram Sang wrote:
> On Wed, Sep 21, 2016 at 08:51:06AM +0200, Jan Glauber wrote:
> > Do not infinitely retry register readq and writeq operations
> > in order to not lock up the CPU in case the TWSI gets stuck.
> > 
> > Return -EIO in case of a failed data read. For all other
> > cases just return so subsequent operations will fail
> > and trigger the recovery.
> > 
> > Signed-off-by: Jan Glauber 
> 
> I didn't really check, but have you considered using
> readq_poll_timeout() from iopoll.h?
> 

Indeed, readq_poll_timeout() fits quite well here. It will lose some cycles
on mips but I'm not convinced that matters with i2c.

That would be the first user of readq_poll_timeout() in the kernel :)

--Jan

Re: [PATCH 5/5] i2c: octeon,thunderx: Limit register access retries

2016-09-21 Thread Wolfram Sang 
On Wed, Sep 21, 2016 at 08:51:06AM +0200, Jan Glauber wrote:
> Do not infinitely retry register readq and writeq operations
> in order to not lock up the CPU in case the TWSI gets stuck.
> 
> Return -EIO in case of a failed data read. For all other
> cases just return so subsequent operations will fail
> and trigger the recovery.
> 
> Signed-off-by: Jan Glauber 

I didn't really check, but have you considered using
readq_poll_timeout() from iopoll.h?



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[PATCH 5/5] i2c: octeon,thunderx: Limit register access retries

2016-09-20 Thread Jan Glauber 
Do not infinitely retry register readq and writeq operations
in order to not lock up the CPU in case the TWSI gets stuck.

Return -EIO in case of a failed data read. For all other
cases just return so subsequent operations will fail
and trigger the recovery.

Signed-off-by: Jan Glauber 
---
 drivers/i2c/busses/i2c-octeon-core.c |  4 +++-
 drivers/i2c/busses/i2c-octeon-core.h | 21 -
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-octeon-core.c 
b/drivers/i2c/busses/i2c-octeon-core.c
index b21aa3e..6ba0146 100644
--- a/drivers/i2c/busses/i2c-octeon-core.c
+++ b/drivers/i2c/busses/i2c-octeon-core.c
@@ -381,7 +381,9 @@ static int octeon_i2c_read(struct octeon_i2c *i2c, int 
target,
if (result)
return result;
 
-   data[i] = octeon_i2c_data_read(i2c);
+   data[i] = octeon_i2c_data_read(i2c, &result);
+   if (result)
+   return result;
if (recv_len && i == 0) {
if (data[i] > I2C_SMBUS_BLOCK_MAX + 1)
return -EPROTO;
diff --git a/drivers/i2c/busses/i2c-octeon-core.h 
b/drivers/i2c/busses/i2c-octeon-core.h
index 87151ea..177d4cc 100644
--- a/drivers/i2c/busses/i2c-octeon-core.h
+++ b/drivers/i2c/busses/i2c-octeon-core.h
@@ -141,11 +141,14 @@ static inline void octeon_i2c_writeq_flush(u64 val, void 
__iomem *addr)
  */
 static inline void octeon_i2c_reg_write(struct octeon_i2c *i2c, u64 eop_reg, 
u8 data)
 {
+   int tries = 100;
u64 tmp;
 
__raw_writeq(SW_TWSI_V | eop_reg | data, i2c->twsi_base + SW_TWSI(i2c));
do {
tmp = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
+   if (--tries < 0)
+   return;
} while ((tmp & SW_TWSI_V) != 0);
 }
 
@@ -163,24 +166,32 @@ static inline void octeon_i2c_reg_write(struct octeon_i2c 
*i2c, u64 eop_reg, u8
  *
  * The I2C core registers are accessed indirectly via the SW_TWSI CSR.
  */
-static inline u8 octeon_i2c_reg_read(struct octeon_i2c *i2c, u64 eop_reg)
+static inline int octeon_i2c_reg_read(struct octeon_i2c *i2c, u64 eop_reg,
+ int *error)
 {
+   int tries = 100;
u64 tmp;
 
__raw_writeq(SW_TWSI_V | eop_reg | SW_TWSI_R, i2c->twsi_base + 
SW_TWSI(i2c));
do {
tmp = __raw_readq(i2c->twsi_base + SW_TWSI(i2c));
+   if (--tries < 0) {
+   /* signal that the returned data is invalid */
+   if (error)
+   *error = -EIO;
+   return 0;
+   }
} while ((tmp & SW_TWSI_V) != 0);
 
return tmp & 0xFF;
 }
 
 #define octeon_i2c_ctl_read(i2c)   \
-   octeon_i2c_reg_read(i2c, SW_TWSI_EOP_TWSI_CTL)
-#define octeon_i2c_data_read(i2c)  \
-   octeon_i2c_reg_read(i2c, SW_TWSI_EOP_TWSI_DATA)
+   octeon_i2c_reg_read(i2c, SW_TWSI_EOP_TWSI_CTL, NULL)
+#define octeon_i2c_data_read(i2c, error)   \
+   octeon_i2c_reg_read(i2c, SW_TWSI_EOP_TWSI_DATA, error)
 #define octeon_i2c_stat_read(i2c)  \
-   octeon_i2c_reg_read(i2c, SW_TWSI_EOP_TWSI_STAT)
+   octeon_i2c_reg_read(i2c, SW_TWSI_EOP_TWSI_STAT, NULL)
 
 /**
  * octeon_i2c_read_int - read the TWSI_INT register
-- 
1.9.1