[i2c] [PATCH 1 of 2] Clean up of i2c-nforce2

Oleg Ryjkov olegr at olegr.ca
Sun Oct 7 08:29:34 CEST 2007


Hi Jean, hi list,

> Hi Oleg,
> 
> Sorry for the late answer.
> 
> On Fri, 31 Aug 2007 00:15:16 -0700, Oleg Ryjkov wrote:
> > This is the first part of the patch that adds a function to reset the
> > nvidia MCP51/55 i2c controller, if something bad happens to it (i.e.
> > a slave sends a wrong byte count during a block transaction).
> >
> > This patch just adds nforce2_check_status function. It was originally
> > written by Hans-Frieder Vogt <hfvogt at gmx.net>, and was posted on this
> > list around October 2006 (see
> > http://lists.lm-sensors.org/pipermail/i2c/2006-October/000380.html).
> > However, unfortunately, he never got around to submitting it to the
> > kernel.
> > The reason that I'm the one sending it is is:
> > - I relied on it for the second part of the patch,
> > - It makes the driver code cleaner/better.
> 
> I agree that it makes the code nicer. For HZ >= 250, it also makes most
> transactions faster. It makes the short transactions slower though
> (those that were fitting in the udelay(500)) for all values of HZ but
> that's probably not a big problem on practice.
> 
Actually, from what I've seen most of the transactions were completed within
2000-3000 usecs anyways(on MCP51) so this change indeed generates some speedup.

> >
> > Signed-off-by: Oleg Ryjkov <olegr at google.com>
> >
> > --- linux-2.6-untouched/drivers/i2c/busses/i2c-nforce2.c      2007-08-13 18:28:26.000000000 -0700
> > +++ linux-2.6/drivers/i2c/busses/i2c-nforce2.c        2007-08-30 19:38:13.000000000 -0700
> > @@ -98,15 +98,39 @@
> >  #define NVIDIA_SMB_PRTCL_BLOCK_DATA          0x0a
> >  #define NVIDIA_SMB_PRTCL_PEC                 0x80
> >
> > +/* Misc definitions */
> > +#define MAX_TIMEOUT  100
> > +
> >  static struct pci_driver nforce2_driver;
> >
> > +static int nforce2_check_status(struct i2c_adapter * adap) {
> 
> Coding style: opening curly brace goes at the beginning of the next
> line.
Changed.
> 
> > +     struct nforce2_smbus *smbus = adap->algo_data;
> > +     int timeout = 0;
> > +     unsigned char temp;
> > +
> > +     do {
> > +             msleep(1);
> > +             temp = inb_p(NVIDIA_SMB_STS);
> > +     } while ((!temp) && (timeout++ < MAX_TIMEOUT));
> > +
> > +     if ((~temp & NVIDIA_SMB_STS_DONE) && (timeout >= MAX_TIMEOUT)) {
> 
> (~temp & NVIDIA_SMB_STS_DONE) is better written
> !(temp & NVIDIA_SMB_STS_DONE).
Changed.
> 
> I think that this test can be simplified. Checking for the DONE bit not
> being set should be enough. If that bit was set, then the while loop
> would have exited before the timeout. Or am I missing something?
> 
I've changed that slightly - first we check whether timeout has been
exceeded, then make sure that DONE bit is one and the status is 0. I
find this more intuitive than before. This way the error messages better
reflect the actual error condition.
> > +             dev_dbg(&adap->dev, "SMBus Timeout (0x%02x)!\n", temp);
> > +             return -1;
> > +     }
> > +     if ((~temp & NVIDIA_SMB_STS_DONE) || (temp & NVIDIA_SMB_STS_STATUS)) {
> 
> Then this test can be simplified as well: no need to check again for
> the DONE bit not being set, as you checked this above already.
> 
See the previous comment.
> > +             dev_dbg(&adap->dev, "Transaction failed (0x%02x)!\n", temp);
> > +             return -1;
> > +     }
> > +     return 0;
> > +}
> > +
> >  /* Return -1 on error */
> >  static s32 nforce2_access(struct i2c_adapter * adap, u16 addr,
> >               unsigned short flags, char read_write,
> >               u8 command, int size, union i2c_smbus_data * data)
> >  {
> >       struct nforce2_smbus *smbus = adap->algo_data;
> > -     unsigned char protocol, pec, temp;
> > +     unsigned char protocol, pec;
> >       u8 len;
> >       int i;
> >
> > @@ -170,22 +194,9 @@
> >       outb_p((addr & 0x7f) << 1, NVIDIA_SMB_ADDR);
> >       outb_p(protocol, NVIDIA_SMB_PRTCL);
> >
> > -     temp = inb_p(NVIDIA_SMB_STS);
> > -
> > -     if (~temp & NVIDIA_SMB_STS_DONE) {
> > -             udelay(500);
> > -             temp = inb_p(NVIDIA_SMB_STS);
> > -     }
> > -     if (~temp & NVIDIA_SMB_STS_DONE) {
> > -             msleep(10);
> > -             temp = inb_p(NVIDIA_SMB_STS);
> > -     }
> > -
> > -     if ((~temp & NVIDIA_SMB_STS_DONE) || (temp & NVIDIA_SMB_STS_STATUS)) {
> > -             dev_dbg(&adap->dev, "SMBus Timeout! (0x%02x)\n", temp);
> > +     if (nforce2_check_status(adap))
> >               return -1;
> > -     }
> > -
> > +
> 
> You patch is introducing trailing white space here, please clean up.
> 
Changed.
> >       if (read_write == I2C_SMBUS_WRITE)
> >               return 0;
> >
> > @@ -202,7 +213,12 @@
> >
> >               case I2C_SMBUS_BLOCK_DATA:
> >                       len = inb_p(NVIDIA_SMB_BCNT);
> > -                     len = min_t(u8, len, I2C_SMBUS_BLOCK_MAX);
> > +                     if ((len <= 0) || (len > I2C_SMBUS_BLOCK_MAX)) {
> > +                             dev_err(&adap->dev, "Transaction failed"
> 
> Missing space at end of string.
Changed.
> 
> > +                                     "(requested block size: 0x%02x)"
> > +                                     "\n", len);
> 
> Please move the \n at the end of the previous line.
Changed.
> 
> > +                             return -1;
> > +                     }
> >                       for (i = 0; i < len; i++)
> >                               data->block[i+1] = inb_p(NVIDIA_SMB_DATA + i);
> >                       data->block[0] = len;
> 
> 
> --
> Jean Delvare

Thank you for the careful review.

Oleg Ryjkov

Signed-off-by: Oleg Ryjkov <olegr at olegr.ca>

--- linux-2.6-untouched/drivers/i2c/busses/i2c-nforce2.c	2007-10-06 20:17:53.000000000 -0400
+++ linux-2.6/drivers/i2c/busses/i2c-nforce2.c	2007-10-07 00:10:14.000000000 -0400
@@ -98,15 +98,40 @@
 #define NVIDIA_SMB_PRTCL_BLOCK_DATA		0x0a
 #define NVIDIA_SMB_PRTCL_PEC			0x80
 
+/* Misc definitions */
+#define MAX_TIMEOUT	100
+
 static struct pci_driver nforce2_driver;
 
+static int nforce2_check_status(struct i2c_adapter *adap)
+{
+	struct nforce2_smbus *smbus = adap->algo_data;
+	int timeout = 0;
+	unsigned char temp;
+
+	do {
+		msleep(1);
+		temp = inb_p(NVIDIA_SMB_STS);
+	} while ((!temp) && (timeout++ < MAX_TIMEOUT));
+
+	if (timeout >= MAX_TIMEOUT) {
+		dev_dbg(&adap->dev, "SMBus Timeout (0x%02x)!\n", temp);
+		return -1;
+	}
+	if (!(temp & NVIDIA_SMB_STS_DONE) || (temp & NVIDIA_SMB_STS_STATUS)) {
+		dev_dbg(&adap->dev, "Transaction failed (0x%02x)!\n", temp);
+		return -1;
+	}
+	return 0;
+}
+
 /* Return -1 on error */
 static s32 nforce2_access(struct i2c_adapter * adap, u16 addr,
 		unsigned short flags, char read_write,
 		u8 command, int size, union i2c_smbus_data * data)
 {
 	struct nforce2_smbus *smbus = adap->algo_data;
-	unsigned char protocol, pec, temp;
+	unsigned char protocol, pec;
 	u8 len;
 	int i;
 
@@ -170,21 +195,8 @@
 	outb_p((addr & 0x7f) << 1, NVIDIA_SMB_ADDR);
 	outb_p(protocol, NVIDIA_SMB_PRTCL);
 
-	temp = inb_p(NVIDIA_SMB_STS);
-
-	if (~temp & NVIDIA_SMB_STS_DONE) {
-		udelay(500);
-		temp = inb_p(NVIDIA_SMB_STS);
-	}
-	if (~temp & NVIDIA_SMB_STS_DONE) {
-		msleep(10);
-		temp = inb_p(NVIDIA_SMB_STS);
-	}
-
-	if ((~temp & NVIDIA_SMB_STS_DONE) || (temp & NVIDIA_SMB_STS_STATUS)) {
-		dev_dbg(&adap->dev, "SMBus Timeout! (0x%02x)\n", temp);
+	if (nforce2_check_status(adap))
 		return -1;
-	}
 
 	if (read_write == I2C_SMBUS_WRITE)
 		return 0;
@@ -202,7 +214,12 @@
 
 		case I2C_SMBUS_BLOCK_DATA:
 			len = inb_p(NVIDIA_SMB_BCNT);
-			len = min_t(u8, len, I2C_SMBUS_BLOCK_MAX);
+			if ((len <= 0) || (len > I2C_SMBUS_BLOCK_MAX)) {
+				dev_err(&adap->dev, "Transaction failed "
+					"(received block size: 0x%02x)\n",
+					len);
+				return -1;
+			}
 			for (i = 0; i < len; i++)
 				data->block[i+1] = inb_p(NVIDIA_SMB_DATA + i);
 			data->block[0] = len;



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