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Message-ID: <1427703252.26464.14.camel@mtksdaap41>
Date: Mon, 30 Mar 2015 16:14:12 +0800
From: Eddie Huang <eddie.huang@...iatek.com>
To: Sascha Hauer <s.hauer@...gutronix.de>
CC: Mark Rutland <mark.rutland@....com>,
Wolfram Sang <wsa@...-dreams.de>,
Doug Anderson <dianders@...omium.org>,
<linux-i2c@...r.kernel.org>,
David Box <david.e.box@...ux.intel.com>,
Lee Jones <lee.jones@...aro.org>,
Jean Delvare <jdelvare@...e.de>,
Xudong Chen <xudong.chen@...iatek.com>,
Boris BREZILLON <boris.brezillon@...e-electrons.com>,
Pawel Moll <pawel.moll@....com>,
Liguo Zhang <liguo.zhang@...iatek.com>,
Wei Yan <sledge.yanwei@...wei.com>,
Bjorn Andersson <bjorn.andersson@...ymobile.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>,
Neelesh Gupta <neelegup@...ux.vnet.ibm.com>,
<devicetree@...r.kernel.org>, Arnd Bergmann <arnd@...db.de>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Beniamino Galvani <b.galvani@...il.com>,
Rob Herring <robh+dt@...nel.org>,
<linux-mediatek@...ts.infradead.org>,
Matthias Brugger <matthias.bgg@...il.com>,
<linux-arm-kernel@...ts.infradead.org>,
<srv_heupstream@...iatek.com>,
Anders Berg <anders.berg@...gotech.com>,
Jim Cromie <jim.cromie@...il.com>,
Simon Glass <sjg@...omium.org>,
Max Schwarz <max.schwarz@...ine.de>,
<linux-kernel@...r.kernel.org>,
Sascha Hauer <kernel@...gutronix.de>,
Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH v5 2/3] I2C: mediatek: Add driver for MediaTek I2C
controller
Hi Sascha,
On Mon, 2015-03-23 at 09:42 +0100, Sascha Hauer wrote:
> On Sat, Mar 21, 2015 at 02:05:21PM +0800, Eddie Huang wrote:
> > From: Xudong Chen <xudong.chen@...iatek.com>
> >
> > The mediatek SoCs have I2C controller that handle I2C transfer.
> > This patch include common I2C bus driver.
> > This driver is compatible with I2C controller on mt65xx/mt81xx.
> >
> > Signed-off-by: Xudong Chen <xudong.chen@...iatek.com>
> > Signed-off-by: Liguo Zhang <liguo.zhang@...iatek.com>
> > Signed-off-by: Eddie Huang <eddie.huang@...iatek.com>
> > ---
> > drivers/i2c/busses/Kconfig | 9 +
> > drivers/i2c/busses/Makefile | 1 +
> > drivers/i2c/busses/i2c-mt65xx.c | 705 ++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 715 insertions(+)
> > create mode 100644 drivers/i2c/busses/i2c-mt65xx.c
> >
> > +
> > +static void mtk_i2c_clock_disable(struct mtk_i2c *i2c)
> > +{
> > + if (i2c->have_pmic)
> > + clk_disable_unprepare(i2c->clk_pmic);
> > +
> > + clk_disable_unprepare(i2c->clk_main);
> > + clk_disable_unprepare(i2c->clk_dma);
> > +}
> > +
> > +static inline void mtk_i2c_init_hw(struct mtk_i2c *i2c)
>
> Please let the compiler decide whether to inline this or not.
Will fix it.
>
> > +{
> > + mtk_i2c_writew(I2C_SOFT_RST, i2c, OFFSET_SOFTRESET);
> > + /* Set ioconfig */
> > + if (i2c->use_push_pull)
> > + mtk_i2c_writew(I2C_IO_CONFIG_PUSH_PULL, i2c, OFFSET_IO_CONFIG);
> > + else
> > + mtk_i2c_writew(I2C_IO_CONFIG_OPEN_DRAIN, i2c, OFFSET_IO_CONFIG);
> > +
> > + if (i2c->platform_compat & COMPAT_MT6577)
> > + mtk_i2c_writew(I2C_DCM_DISABLE, i2c, OFFSET_DCM_EN);
> > +
> > + mtk_i2c_writew(i2c->timing_reg, i2c, OFFSET_TIMING);
> > + mtk_i2c_writew(i2c->high_speed_reg, i2c, OFFSET_HS);
> > +}
> > +
>
> [...]
>
> > + step_cnt = step_div;
> > + sclk = hclk / (2 * sample_cnt * step_cnt);
> > + if (sclk > khz) {
> > + dev_dbg(i2c->dev, "%s mode: unsupported speed (%ldkhz)\n",
> > + (mode == HS_MODE) ? "HS" : "ST/FT", (long int)khz);
> > + return -ENOTSUPP;
> > + }
> > +
> > + step_cnt--;
> > + sample_cnt--;
> > +
> > + if (mode == HS_MODE) {
>
> This is the only place where the HS_MODE is actually tested for.
> Dropping this enum and using i2c->speed_hz > MAX_FS_MODE_SPEED directly
> here would improve readability.
Will fix it.
>
> > + /* Set the hign speed mode register */
> > + i2c->timing_reg = I2C_FS_TIME_INIT_VALUE;
> > + i2c->high_speed_reg = I2C_TIME_DEFAULT_VALUE |
> > + (sample_cnt & I2C_TIMING_SAMPLE_COUNT_MASK) << 12 |
> > + (step_cnt & I2C_TIMING_SAMPLE_COUNT_MASK) << 8;
> > + } else {
> > + i2c->timing_reg =
> > + (sample_cnt & I2C_TIMING_SAMPLE_COUNT_MASK) << 8 |
> > + (step_cnt & I2C_TIMING_STEP_DIV_MASK) << 0;
> > + /* Disable the high speed transaction */
> > + i2c->high_speed_reg = I2C_TIME_CLR_VALUE;
> > + }
> > +
> > + return 0;
> > +}
> > +
>
> [...]
>
> > + if (i2c->speed_hz > 400000)
> > + control_reg |= I2C_CONTROL_RS;
> > + if (i2c->op == I2C_MASTER_WRRD)
> > + control_reg |= I2C_CONTROL_DIR_CHANGE | I2C_CONTROL_RS;
> > + mtk_i2c_writew(control_reg, i2c, OFFSET_CONTROL);
> > +
> > + /* set start condition */
> > + if (i2c->speed_hz <= 100000)
> > + mtk_i2c_writew(I2C_ST_START_CON, i2c, OFFSET_EXT_CONF);
> > + else
> > + mtk_i2c_writew(I2C_FS_START_CON, i2c, OFFSET_EXT_CONF);
> > +
> > + if (~control_reg & I2C_CONTROL_RS)
> > + mtk_i2c_writew(I2C_DELAY_LEN, i2c, OFFSET_DELAY_LEN);
>
> speed <= 400000 here to make this more obvious?
There are two cases, not only speed<=400000, but I2C_MASTER_WRRD. I tend
to keep it.
>
> > +
> > + addr_reg = msgs->addr << 1;
> > + if (i2c->op == I2C_MASTER_RD)
> > + addr_reg |= 0x1;
> > + mtk_i2c_writew(addr_reg, i2c, OFFSET_SLAVE_ADDR);
> > +
> > + /* Clear interrupt status */
> > + mtk_i2c_writew(I2C_HS_NACKERR | I2C_ACKERR | I2C_TRANSAC_COMP,
> > + i2c, OFFSET_INTR_STAT);
> > + mtk_i2c_writew(I2C_FIFO_ADDR_CLR, i2c, OFFSET_FIFO_ADDR_CLR);
> > +
> > + /* Enable interrupt */
> > + mtk_i2c_writew(I2C_HS_NACKERR | I2C_ACKERR | I2C_TRANSAC_COMP,
> > + i2c, OFFSET_INTR_MASK);
>
> Why do you enable/disable interrupts for each transfer? Enabling them
> once and just acknowledge them in the interrupt handler should be
> enough.
This can avoid unwanted I2C interrupt. For example, I2C transfer error,
and cause timeout, I2C driver report error to caller. Then I2C error
interrupt happen.
> > + if (!i2c->trans_stop && tmo == 0) {
> > + dev_dbg(i2c->dev, "addr: %x, transfer timeout\n", msgs->addr);
> > + mtk_i2c_init_hw(i2c);
> > + return -ETIMEDOUT;
> > + }
> > +
> > + spin_lock(&i2c->irqlock);
> > + irqstat = i2c->irq_stat;
> > + spin_unlock(&i2c->irqlock);
>
> A plain spin_lock can't protect you against the interrupt handler, see
> https://www.kernel.org/pub/linux/kernel/people/rusty/kernel-locking/c214.html.
> You need at least spin_lock_irq().
>
> Anyway, I think this spin_lock can be removed since it only protects the
> irq_stat variable. This is written only in the interrupt handler and
> then tested for in thread context. The thread waits for the interrupt
> handler to be finished anyway.
Will fix it.
>
> > +static irqreturn_t mtk_i2c_irq(int irqno, void *dev_id)
> > +{
> > + struct mtk_i2c *i2c = dev_id;
> > +
> > + /* Clear interrupt mask */
> > + mtk_i2c_writew(~(I2C_HS_NACKERR | I2C_ACKERR | I2C_TRANSAC_COMP),
> > + i2c, OFFSET_INTR_MASK);
> > +
> > + spin_lock(&i2c->irqlock);
> > + i2c->irq_stat = mtk_i2c_readw(i2c, OFFSET_INTR_STAT);
> > + i2c->trans_stop = true;
>
> A struct completion seems more what you want here. This makes the
> trans_stop variable unnecessary (it contains no information anyway).
>
> See the tegra driver as an example.
OK, will change to use complete API
>
> > + spin_unlock(&i2c->irqlock);
> > + mtk_i2c_writew(I2C_HS_NACKERR | I2C_ACKERR
> > + | I2C_TRANSAC_COMP, i2c, OFFSET_INTR_STAT);
> > + wake_up(&i2c->wait);
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
>
> [...]
>
> > +static int mtk_i2c_probe(struct platform_device *pdev)
> > +{
> > + int ret = 0;
> > + struct mtk_i2c *i2c;
> > + struct clk *clk;
> > + unsigned int clk_src_in_hz;
> > + unsigned int clk_src_div;
> > + struct resource *res;
> > +
> > + i2c = devm_kzalloc(&pdev->dev, sizeof(struct mtk_i2c), GFP_KERNEL);
>
> sizeof(*i2c) instead. This will make it harder to allocate the memory
> for a wrong struct size.
Will fix it.
>
> > + if (i2c == NULL)
> > + return -ENOMEM;
> > +
> > + ret = mtk_i2c_parse_dt(pdev->dev.of_node, i2c, &clk_src_div);
> > + if (ret)
> > + return -EINVAL;
> > +
> > + i2c->platform_compat = mtk_get_device_prop(pdev);
> > + if (i2c->have_pmic && (i2c->platform_compat & COMPAT_MT6577))
> > + return -EINVAL;
> > +
> > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +
> > + i2c->base = devm_ioremap_resource(&pdev->dev, res);
> > + if (IS_ERR(i2c->base))
> > + return PTR_ERR(i2c->base);
> > +
> > + res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> > +
> > + i2c->pdmabase = devm_ioremap_resource(&pdev->dev, res);
> > + if (IS_ERR(i2c->pdmabase))
> > + return PTR_ERR(i2c->pdmabase);
> > +
> > + i2c->irqnr = platform_get_irq(pdev, 0);
> > + if (i2c->irqnr <= 0)
> > + return -EINVAL;
>
> i2c->irqnr is never used outside this function, so you can drop it from
> struct mtk_i2c and make this a local variable.
>
> Contrary to what Uwe said this variable should be a signed variable
> because platform_get_irq() returns a signed integer which may contain a
> negative error code. This will never be catched if you use an unsigned
> variable.
>
> Also you should forward the error instead of returning -EINVAL.
Will fix it.
>
> > +static int mtk_i2c_remove(struct platform_device *pdev)
> > +{
> > + struct mtk_i2c *i2c = platform_get_drvdata(pdev);
> > +
> > + i2c_del_adapter(&i2c->adap);
> > + platform_set_drvdata(pdev, NULL);
>
> This is unnecessary. This pointer is unused when no driver is bound to
> the device and no driver will expect it to be valid in probe().
Will fix it.
Eddie
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