From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Subject: Re: [PATCH 2/2] i2c: (algo-pca) Fix mode selection for PCA9665 Date: Thu, 13 Sep 2012 06:44:39 -0700 Message-ID: <20120913134439.GA1400@roeck-us.net> References: <1347507591-32352-1-git-send-email-linux@roeck-us.net> <1347507591-32352-2-git-send-email-linux@roeck-us.net> <20120913100530.GD14237@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20120913100530.GD14237-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang Cc: Jean Delvare , Ben Dooks , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Thomas Kavanagh , Guenter Roeck List-Id: linux-i2c@vger.kernel.org On Thu, Sep 13, 2012 at 12:05:31PM +0200, Wolfram Sang wrote: > On Wed, Sep 12, 2012 at 08:39:51PM -0700, Guenter Roeck wrote: > > From: Thomas Kavanagh > > > > As implemented, the code always selects turbo mode for PCA9665, no matter which > > clock frequency is configured. This is because it compares clock boundaries > > against constants reflecting (boundary / 100), but uses the actual clock frequency > > to compare against. To fix the problem, use a variable reflecting (clock / 100), > > not the actual clock frequency, when comparing against (boundary / 100). > > Good point, however... > > > > > Cc: Wolfram Sang > > Signed-off-by: Thomas Kavanagh > > Signed-off-by: Guenter Roeck > > --- > > drivers/i2c/algos/i2c-algo-pca.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/i2c/algos/i2c-algo-pca.c b/drivers/i2c/algos/i2c-algo-pca.c > > index 07ccbef..572251b 100644 > > --- a/drivers/i2c/algos/i2c-algo-pca.c > > +++ b/drivers/i2c/algos/i2c-algo-pca.c > > @@ -477,17 +477,17 @@ static int pca_init(struct i2c_adapter *adap) > > /* To avoid integer overflow, use clock/100 for calculations */ > > clock = pca_clock(pca_data) / 100; > > > > - if (pca_data->i2c_clock > 10000) { > > + if (clock > 10000) { > > ... we should make the code more readable if we are at it. > I'd suggest to drop the "/ 100" from above and move it below this > if-block. This will allow for much more readable comparisons, e.g. > "clock > 1000000" etc which is really the clock in Hz. > We can simply compare against the real frequency: if (pca_data->i2c_clock > 1000000) { which also makes the description a bit easier to understand. > > mode = I2C_PCA_MODE_TURBO; > > min_tlow = 14; > > min_thi = 5; > > raise_fall_time = 22; /* Raise 11e-8s, Fall 11e-8s */ > > - } else if (pca_data->i2c_clock > 4000) { > > + } else if (clock > 4000) { > > mode = I2C_PCA_MODE_FASTP; > > min_tlow = 17; > > min_thi = 9; > > raise_fall_time = 22; /* Raise 11e-8s, Fall 11e-8s */ > > - } else if (pca_data->i2c_clock > 1000) { > > + } else if (clock > 1000) { > > mode = I2C_PCA_MODE_FAST; > > min_tlow = 44; > > min_thi = 20; > > -- > > 1.7.9.7 > > > > -- > Pengutronix e.K. | Wolfram Sang | > Industrial Linux Solutions | http://www.pengutronix.de/ |