| Message ID | 20200917052256.5770-3-sultan@kerneltoast.com |
|---|---|
| State | New |
| Headers | show |
| Series | i2c-hid: Save power by reducing i2c xfers with block reads | expand |
On Wed, Sep 16, 2020 at 10:22:54PM -0700, Sultan Alsawaf wrote: > From: Sultan Alsawaf <sultan@kerneltoast.com> > > The point of adding a byte to len in i2c_dw_recv_len() is to make sure > that tx_buf_len is nonzero, so that i2c_dw_xfer_msg() can let the i2c > controller know that the i2c transaction can end. Otherwise, the i2c > controller will think that the transaction can never end for block > reads, which results in the stop-detection bit never being set and thus > the transaction timing out. > > Adding a byte to len is not a reliable way to do this though; sometimes > it lets tx_buf_len become zero, which results in the scenario described > above. Therefore, just directly ensure tx_buf_len cannot be zero to fix > the issue. I got only patch 2/4, where the other 3 along with cover letter?
On 9/17/20 8:22 AM, Sultan Alsawaf wrote: > From: Sultan Alsawaf <sultan@kerneltoast.com> > > The point of adding a byte to len in i2c_dw_recv_len() is to make sure > that tx_buf_len is nonzero, so that i2c_dw_xfer_msg() can let the i2c > controller know that the i2c transaction can end. Otherwise, the i2c > controller will think that the transaction can never end for block > reads, which results in the stop-detection bit never being set and thus > the transaction timing out. > > Adding a byte to len is not a reliable way to do this though; sometimes > it lets tx_buf_len become zero, which results in the scenario described > above. Therefore, just directly ensure tx_buf_len cannot be zero to fix > the issue. > > Fixes: c3ae106050b9 ("i2c: designware: Implement support for SMBus block read and write") > Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> > --- > drivers/i2c/busses/i2c-designware-master.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > Were other patches in series dropped somewhere? I received only this. Jarkko
On Thu, Sep 17, 2020 at 04:44:18PM +0300, Jarkko Nikula wrote: > On 9/17/20 8:22 AM, Sultan Alsawaf wrote: > > From: Sultan Alsawaf <sultan@kerneltoast.com> > > > > The point of adding a byte to len in i2c_dw_recv_len() is to make sure > > that tx_buf_len is nonzero, so that i2c_dw_xfer_msg() can let the i2c > > controller know that the i2c transaction can end. Otherwise, the i2c > > controller will think that the transaction can never end for block > > reads, which results in the stop-detection bit never being set and thus > > the transaction timing out. > > > > Adding a byte to len is not a reliable way to do this though; sometimes > > it lets tx_buf_len become zero, which results in the scenario described > > above. Therefore, just directly ensure tx_buf_len cannot be zero to fix > > the issue. > > > > Fixes: c3ae106050b9 ("i2c: designware: Implement support for SMBus block read and write") > > Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> > > --- > > drivers/i2c/busses/i2c-designware-master.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > Were other patches in series dropped somewhere? I received only this. @linux.intel.com has some issues in delivery (accepting) messages. You may download thru lore.kernel.org entire series and reply.
diff --git a/drivers/i2c/busses/i2c-designware-master.c b/drivers/i2c/busses/i2c-designware-master.c index d78f48ca4886..22f28516bca7 100644 --- a/drivers/i2c/busses/i2c-designware-master.c +++ b/drivers/i2c/busses/i2c-designware-master.c @@ -395,8 +395,9 @@ i2c_dw_recv_len(struct dw_i2c_dev *dev, u8 len) * Adjust the buffer length and mask the flag * after receiving the first byte. */ - len += (flags & I2C_CLIENT_PEC) ? 2 : 1; - dev->tx_buf_len = len - min_t(u8, len, dev->rx_outstanding); + if (flags & I2C_CLIENT_PEC) + len++; + dev->tx_buf_len = len - min_t(u8, len - 1, dev->rx_outstanding); msgs[dev->msg_read_idx].len = len; msgs[dev->msg_read_idx].flags &= ~I2C_M_RECV_LEN;