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Message-ID: <20150518184300.GB28888@pengutronix.de>
Date: Mon, 18 May 2015 20:43:00 +0200
From: Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>
To: Eddie Huang <eddie.huang@...iatek.com>
Cc: Wolfram Sang <wsa@...-dreams.de>, srv_heupstream@...iatek.com,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Matthias Brugger <matthias.bgg@...il.com>,
Xudong Chen <xudong.chen@...iatek.com>,
Liguo Zhang <liguo.zhang@...iatek.com>,
linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org,
Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH v8 2/3] I2C: mediatek: Add driver for MediaTek I2C
controller
Hello,
On Tue, May 19, 2015 at 12:40:08AM +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>
> Acked-by: Sascha Hauer <s.hauer@...gutronix.de>
> ---
> drivers/i2c/busses/Kconfig | 9 +
> drivers/i2c/busses/Makefile | 1 +
> drivers/i2c/busses/i2c-mt65xx.c | 675 ++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 685 insertions(+)
> create mode 100644 drivers/i2c/busses/i2c-mt65xx.c
>
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 2255af2..14c7266 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -620,6 +620,15 @@ config I2C_MPC
> This driver can also be built as a module. If so, the module
> will be called i2c-mpc.
>
> +config I2C_MT65XX
> + tristate "MediaTek I2C adapter"
> + depends on ARCH_MEDIATEK || COMPILE_TEST
> + help
> + This selects the MediaTek(R) Integrated Inter Circuit bus driver
> + for MT65xx and MT81xx.
> + If you want to use MediaTek(R) I2C interface, say Y or M here.
> + If unsure, say N.
> +
> config I2C_MV64XXX
> tristate "Marvell mv64xxx I2C Controller"
> depends on MV64X60 || PLAT_ORION || ARCH_SUNXI
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index cdf941d..abbf422 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -60,6 +60,7 @@ obj-$(CONFIG_I2C_JZ4780) += i2c-jz4780.o
> obj-$(CONFIG_I2C_KEMPLD) += i2c-kempld.o
> obj-$(CONFIG_I2C_MESON) += i2c-meson.o
> obj-$(CONFIG_I2C_MPC) += i2c-mpc.o
> +obj-$(CONFIG_I2C_MT65XX) += i2c-mt65xx.o
> obj-$(CONFIG_I2C_MV64XXX) += i2c-mv64xxx.o
> obj-$(CONFIG_I2C_MXS) += i2c-mxs.o
> obj-$(CONFIG_I2C_NOMADIK) += i2c-nomadik.o
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> new file mode 100644
> index 0000000..7462f05
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -0,0 +1,675 @@
> +/*
> + * Copyright (c) 2014 MediaTek Inc.
> + * Author: Xudong.chen <xudong.chen@...iatek.com>
s/Xudong.chen/Xudong Chen/
> +#define I2C_DRV_NAME "mt-i2c"
i2c-mt65xx ?
> +}
> +
> +/* calculate i2c port speed */
It would be nice to summarize the clock frequency settings here.
Something like:
/*
* The input clock is divided by the value specified in the
* device tree as clock-div. The actual bus speed is then
* derived from this frequency by the following formula:
* ....
This would make it possible to verify your calculations below.
> +static int mtk_i2c_set_speed(struct mtk_i2c *i2c, unsigned int clk_src_in_hz)
> +{
> + unsigned int khz;
> + unsigned int step_cnt;
> + unsigned int sample_cnt;
> + unsigned int sclk;
> + unsigned int hclk;
> + unsigned int max_step_cnt;
> + unsigned int sample_div = MAX_SAMPLE_CNT_DIV;
> + unsigned int step_div;
> + unsigned int min_div;
> + unsigned int best_mul;
> + unsigned int cnt_mul;
> +
> + if (i2c->speed_hz > MAX_HS_MODE_SPEED)
> + return -EINVAL;
> + else if (i2c->speed_hz > MAX_FS_MODE_SPEED)
> + max_step_cnt = MAX_HS_STEP_CNT_DIV;
> + else
> + max_step_cnt = MAX_STEP_CNT_DIV;
> +
> + step_div = max_step_cnt;
> + /* Find the best combination */
> + khz = i2c->speed_hz / 1000;
> + hclk = clk_src_in_hz / 1000;
> + min_div = ((hclk >> 1) + khz - 1) / khz;
This is DIV_ROUND_UP(hclk >> 1, khz).
> + best_mul = MAX_SAMPLE_CNT_DIV * max_step_cnt;
> +
> + for (sample_cnt = 1; sample_cnt <= MAX_SAMPLE_CNT_DIV; sample_cnt++) {
> + step_cnt = (min_div + sample_cnt - 1) / sample_cnt;
> + cnt_mul = step_cnt * sample_cnt;
> + if (step_cnt > max_step_cnt)
> + continue;
> +
> + if (cnt_mul < best_mul) {
> + best_mul = cnt_mul;
> + sample_div = sample_cnt;
> + step_div = step_cnt;
> + if (best_mul == min_div)
> + break;
> + }
> + }
> +
> + sample_cnt = sample_div;
> + step_cnt = step_div;
> + sclk = hclk / (2 * sample_cnt * step_cnt);
> + if (sclk > khz) {
> + dev_dbg(i2c->dev, "%s mode: unsupported speed (%ldkhz)\n",
> + (i2c->speed_hz > MAX_HS_MODE_SPEED) ? "HS" : "ST/FT",
> + (long int)khz);
> + return -EINVAL;
> + }
> +
> + step_cnt--;
> + sample_cnt--;
> +
> + if (i2c->speed_hz > MAX_FS_MODE_SPEED) {
> + /* 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;
Can it happen that sample_cnt & I2C_TIMING_SAMPLE_COUNT_MASK !=
sample_cnt? If yes, what is the influence on correctness? Same question
for step_cnt.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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