On 01-17 11:25, Ivan T. Ivanov wrote: > Date: Mon, 17 Jan 2022 11:25:04 +0100 > From: "Ivan T. Ivanov" <iivanov@xxxxxxx> > To: Florian Fainelli <f.fainelli@xxxxxxxxx>, Ray Jui <rjui@xxxxxxxxxxxx>, > Scott Branden <sbranden@xxxxxxxxxxxx>, Nicolas Saenz Julienne > <nsaenz@xxxxxxxxxx> > Cc: linux-i2c@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Phil > Elwell <phil@xxxxxxxxxxxxxxx>, "Ivan T . Ivanov" <iivanov@xxxxxxx> > Subject: [PATCH] i2c: bcm2835: Set clock-stretch timeout to 35ms > Message-Id: <20220117102504.90585-1-iivanov@xxxxxxx> Tags: all arm i2c linux me ring rpi sent Hi, > > From: Phil Elwell <phil@xxxxxxxxxxxxxxx> > > The BCM2835 I2C blocks have a register to set the clock-stretch > timeout - how long the device is allowed to hold SCL low - in bus > cycles. The current driver doesn't write to the register, therefore > the default value of 64 cycles is being used for all devices. > > Set the timeout to the value recommended for SMBus - 35ms. > > See: https://github.com/raspberrypi/linux/issues/3064 It will be nice if we have this fix upstream. Regards, Ivan > > Signed-off-by: Phil Elwell <phil@xxxxxxxxxxxxxxx> > [iivanov@xxxxxxx fix small coding style issue] > Signed-off-by: Ivan T. Ivanov <iivanov@xxxxxxx> > --- > drivers/i2c/busses/i2c-bcm2835.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c > index 37443edbf754..9cce0e15da32 100644 > --- a/drivers/i2c/busses/i2c-bcm2835.c > +++ b/drivers/i2c/busses/i2c-bcm2835.c > @@ -106,6 +106,7 @@ static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate, > { > struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw); > u32 redl, fedl; > + u32 clk_tout; > u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate); > > if (divider == -EINVAL) > @@ -129,6 +130,17 @@ static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate, > bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL, > (fedl << BCM2835_I2C_FEDL_SHIFT) | > (redl << BCM2835_I2C_REDL_SHIFT)); > + > + /* > + * Set the clock stretch timeout to the SMBUs-recommended 35ms. > + */ > + if (rate > 0xffff * 1000 / 35) > + clk_tout = 0xffff; > + else > + clk_tout = 35 * rate / 1000; > + > + bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_CLKT, clk_tout); > + > return 0; > } > > -- > 2.26.2 >
