From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Zhao Subject: Re: [PATCH 1/4] i2c: imx: check busy bit when START/STOP Date: Thu, 1 Oct 2009 22:54:46 +0800 Message-ID: <4e090d470910010754r1ebc4455u6220ccfd803491b0@mail.gmail.com> References: <1254359613-21210-1-git-send-email-linuxzsc@gmail.com> <4e090d470910010103o611d9fb2t3acf93632216fc88@mail.gmail.com> <20091001083831.GD27039@pengutronix.de> <4e090d470910010211k4ce78763i1a5163ec6ea57fe8@mail.gmail.com> <20091001095239.GE27039@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20091001095239.GE27039-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sascha Hauer Cc: kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org List-Id: linux-i2c@vger.kernel.org On Thu, Oct 1, 2009 at 5:52 PM, Sascha Hauer w= rote: > On Thu, Oct 01, 2009 at 05:11:30PM +0800, Richard Zhao wrote: >> On Thu, Oct 1, 2009 at 4:38 PM, Sascha Hauer wrote: >> > On Thu, Oct 01, 2009 at 04:03:20PM +0800, Richard Zhao wrote: >> >> On Thu, Oct 1, 2009 at 9:13 AM, Richard Zhao = wrote: >> >> > After START/RESTART, wait for busy bit to be set and >> >> > after STOP, wait for busy bit to be clear. >> >> > >> >> > Signed-off-by: Richard Zhao >> >> > >> >> > diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/= i2c-imx.c >> >> > index 4afba3e..156cc95 100644 >> >> > --- a/drivers/i2c/busses/i2c-imx.c >> >> > +++ b/drivers/i2c/busses/i2c-imx.c >> >> > @@ -125,14 +125,19 @@ struct imx_i2c_struct { >> >> > =A0/** Functions for IMX I2C adapter driver *******************= ******************** >> >> > =A0************************************************************= *******************/ >> >> > >> >> > -static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx) >> >> > +static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, in= t for_busy) >> >> > =A0{ >> >> > =A0 =A0 =A0 =A0unsigned long orig_jiffies =3D jiffies; >> >> > + =A0 =A0 =A0 unsigned int temp; >> >> > >> >> > =A0 =A0 =A0 =A0dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func_= _); >> >> > >> >> > - =A0 =A0 =A0 /* wait for bus not busy */ >> >> > - =A0 =A0 =A0 while (readb(i2c_imx->base + IMX_I2C_I2SR) & I2SR= _IBB) { >> >> > + =A0 =A0 =A0 temp =3D readb(i2c_imx->base + IMX_I2C_I2SR); >> >> > + =A0 =A0 =A0 while (1) { >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (for_busy && (temp & I2SR_IBB)= ) >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break; >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (!for_busy && !(temp & I2SR_IB= B)) >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 break; >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (signal_pending(current)) { >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0dev_dbg(&i2c_imx= ->adapter.dev, >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= "<%s> I2C Interrupted\n", __func__); >> >> > @@ -144,6 +149,7 @@ static int i2c_imx_bus_busy(struct imx_i2c_= struct *i2c_imx) >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0return -EIO; >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0schedule(); >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 temp =3D readb(i2c_imx->base + IM= X_I2C_I2SR); >> >> > =A0 =A0 =A0 =A0} >> >> > >> >> > =A0 =A0 =A0 =A0return 0; >> >> > @@ -179,20 +185,32 @@ static int i2c_imx_acked(struct imx_i2c_s= truct *i2c_imx) >> >> > =A0 =A0 =A0 =A0return 0; >> >> > =A0} >> >> > >> >> > -static void i2c_imx_start(struct imx_i2c_struct *i2c_imx) >> >> > +static int i2c_imx_start(struct imx_i2c_struct *i2c_imx) >> >> > =A0{ >> >> > =A0 =A0 =A0 =A0unsigned int temp =3D 0; >> >> > + =A0 =A0 =A0 int result; >> >> > >> >> > =A0 =A0 =A0 =A0dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func_= _); >> >> > >> >> > =A0 =A0 =A0 =A0/* Enable I2C controller */ >> >> > + =A0 =A0 =A0 writeb(0, i2c_imx->base + IMX_I2C_I2SR); >> >> > =A0 =A0 =A0 =A0writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR); >> >> > + >> >> > + =A0 =A0 =A0 result =3D i2c_imx_bus_busy(i2c_imx, 0); >> >> > + =A0 =A0 =A0 if (result) >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 return result; >> >> > + >> >> > =A0 =A0 =A0 =A0/* Start I2C transaction */ >> >> > =A0 =A0 =A0 =A0temp =3D readb(i2c_imx->base + IMX_I2C_I2CR); >> >> > =A0 =A0 =A0 =A0temp |=3D I2CR_MSTA; >> >> > =A0 =A0 =A0 =A0writeb(temp, i2c_imx->base + IMX_I2C_I2CR); >> >> > + =A0 =A0 =A0 result =3D i2c_imx_bus_busy(i2c_imx, 1); >> >> > + =A0 =A0 =A0 if (result) >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 return result; >> >> > + >> >> > =A0 =A0 =A0 =A0temp |=3D I2CR_IIEN | I2CR_MTX | I2CR_TXAK; >> >> > =A0 =A0 =A0 =A0writeb(temp, i2c_imx->base + IMX_I2C_I2CR); >> >> > + =A0 =A0 =A0 return result; >> >> > =A0} >> >> > >> >> > =A0static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx) >> >> > @@ -202,16 +220,16 @@ static void i2c_imx_stop(struct imx_i2c_s= truct *i2c_imx) >> >> > =A0 =A0 =A0 =A0/* Stop I2C transaction */ >> >> > =A0 =A0 =A0 =A0dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func_= _); >> >> > =A0 =A0 =A0 =A0temp =3D readb(i2c_imx->base + IMX_I2C_I2CR); >> >> > - =A0 =A0 =A0 temp &=3D ~I2CR_MSTA; >> >> > + =A0 =A0 =A0 temp &=3D ~(I2CR_MSTA | I2CR_MTX); >> >> > =A0 =A0 =A0 =A0writeb(temp, i2c_imx->base + IMX_I2C_I2CR); >> >> > - =A0 =A0 =A0 /* setup chip registers to defaults */ >> >> > - =A0 =A0 =A0 writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR); >> >> > - =A0 =A0 =A0 writeb(0, i2c_imx->base + IMX_I2C_I2SR); >> >> > =A0 =A0 =A0 =A0/* >> >> > =A0 =A0 =A0 =A0 * This delay caused by an i.MXL hardware bug. >> >> > =A0 =A0 =A0 =A0 * If no (or too short) delay, no "STOP" bit wil= l be generated. >> >> > =A0 =A0 =A0 =A0 */ >> >> > =A0 =A0 =A0 =A0udelay(i2c_imx->disable_delay); >> >> > + >> >> > + =A0 =A0 =A0 i2c_imx_bus_busy(i2c_imx, 0); >> >> > + >> >> > =A0 =A0 =A0 =A0/* Disable I2C controller */ >> >> > =A0 =A0 =A0 =A0writeb(0, i2c_imx->base + IMX_I2C_I2CR); >> >> > =A0} >> >> > @@ -344,7 +362,7 @@ static int i2c_imx_read(struct imx_i2c_stru= ct *i2c_imx, struct i2c_msg *msgs) >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0dev_dbg(&i2c_imx= ->adapter.dev, >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= "<%s> clear MSTA\n", __func__); >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0temp =3D readb(i= 2c_imx->base + IMX_I2C_I2CR); >> >> > - =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 temp &=3D ~I2CR_M= STA; >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 temp &=3D ~(I2CR_= MSTA | I2CR_MTX); >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0writeb(temp, i2c= _imx->base + IMX_I2C_I2CR); >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} else if (i =3D=3D (msgs->len -= 2)) { >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0dev_dbg(&i2c_imx= ->adapter.dev, >> >> > @@ -370,14 +388,11 @@ static int i2c_imx_xfer(struct i2c_adapte= r *adapter, >> >> > >> >> > =A0 =A0 =A0 =A0dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func_= _); >> >> > >> >> > - =A0 =A0 =A0 /* Check if i2c bus is not busy */ >> >> > - =A0 =A0 =A0 result =3D i2c_imx_bus_busy(i2c_imx); >> >> > + =A0 =A0 =A0 /* Start I2C transfer */ >> >> > + =A0 =A0 =A0 result =3D i2c_imx_start(i2c_imx); >> >> > =A0 =A0 =A0 =A0if (result) >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0goto fail0; >> >> > >> >> > - =A0 =A0 =A0 /* Start I2C transfer */ >> >> > - =A0 =A0 =A0 i2c_imx_start(i2c_imx); >> >> > - >> >> > =A0 =A0 =A0 =A0/* read/write data */ >> >> > =A0 =A0 =A0 =A0for (i =3D 0; i < num; i++) { >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (i) { >> >> > @@ -386,6 +401,9 @@ static int i2c_imx_xfer(struct i2c_adapter = *adapter, >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0temp =3D readb(i= 2c_imx->base + IMX_I2C_I2CR); >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0temp |=3D I2CR_R= STA; >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0writeb(temp, i2c= _imx->base + IMX_I2C_I2CR); >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 result =3D =A0i2c= _imx_bus_busy(i2c_imx, 1); >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (result) >> >> > + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 g= oto fail0; >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0} >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0dev_dbg(&i2c_imx->adapter.dev, >> >> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0"<%s> transfer m= essage: %d\n", __func__, i); >> >> > -- >> >> > 1.6.0.4 >> >> > >> >> > >> >> >> >> Hi Sascha, >> >> >> >> So I assume you have no comments about this patch ? >> > >> > No, I'm still thinking about it. The commit message says *what* yo= u're >> > doing, but not *why*. Is it a concrete bug that you fix or is it j= ust >> > because it might be a good idea to do so? >> The driver doesn't work with mx51, which is a fast cpu. So I checked >> the driver, and find it didn't check IBB. > > Ah, so 'make the driver work on i.MX51' is a good statement which sho= uld > be part of the commit message. Well, maybe I can mention it. But I think the good point is to present what you modified, not the sid= e effect. > >> > Also, we leave i2c_imx_xfer with the controller in a well defined = state. >> > So if we leave this function with the controller in non busy state= , why >> > do we have to check for non busy again when we enter it again? >> I2C is a multi-master bus. > > So you say with this patch the driver becomes multi master capable? I= f > so, it should also be part of the commit message. Yes. But I don't have multi-master system. So I can't say that. The code is just taken from Freescale latest code. Without it, It could also cause a device error. I forget the details. Anyway, it doesn't make anything wrong. Thanks Richard > > Sascha > > > -- > Pengutronix e.K. =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = | =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | > Industrial Linux Solutions =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | http://w= ww.pengutronix.de/ =A0| > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0= =A0 =A0| > Amtsgericht Hildesheim, HRA 2686 =A0 =A0 =A0 =A0 =A0 | Fax: =A0 +49-5= 121-206917-5555 | >