Re: [PATCH 1/2] i2c: imx: I2C Driver doesn't consider I2C_IPGCLK_SEL RCW bit when using ls1046a SoC

[Sascha Hauer <s.hauer@pengutronix.de>]

Hi,

In case we end up with the handling of this issue in the i2c driver,
here are the things to consider for v2.

On Tue, Apr 30, 2019 at 12:47:18PM +0800, Chuanhua Han wrote:
> The current kernel driver does not consider I2C_IPGCLK_SEL (424 bit
> of RCW) in deciding  i2c_clk_rate in function i2c_imx_set_clk()
> { 0 Platform clock/4, 1 Platform clock/2}.
> 
> When using ls1046a SoC, this populates incorrect value in IBFD register
> if I2C_IPGCLK_SEL = 0, which generates half of the desired Clock.
> 
> Therefore, if ls1046a SoC is used, we need to set the i2c clock
> according to the corresponding RCW.
> 
> Signed-off-by: Sumit Batra <sumit.batra@nxp.com>
> Signed-off-by: Chuanhua Han <chuanhua.han@nxp.com>
> ---
>  drivers/i2c/busses/i2c-imx.c | 64 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 64 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index 422f1a445b55..7186cf3c7d24 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -45,6 +45,8 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/sched.h>
>  #include <linux/slab.h>
> +#include <linux/fsl/guts.h>
> +#include <linux/sys_soc.h>
>  
>  /* This will be the driver name the kernel reports */
>  #define DRIVER_NAME "imx-i2c"
> @@ -109,6 +111,21 @@
>  
>  #define I2C_PM_TIMEOUT		10 /* ms */
>  
> +/* 14-1 Since array index starts from 0 */
> +#define RCW_I2C_IPGCLK_WORD (14 - 1)
> +/*
> + * Set mask for RCW 424th bit, reading from DCFG_CCSR RCW Status Registers
> + * Since this register in RM depicted as big endian,
> + * so consider 31st bit as LSB for creating the mask.
> + */
> +#define RCW_I2C_IPGCLK_MASK    0x800000
> +int i2c_ipgclk_sel = 1;

should be static.

> +
> +static const struct soc_device_attribute ls1046a_soc[] = {
> +	       {.family = "QorIQ LS1046A"},
> +	       { /* sentinel */ }
> +};
> +
>  /*
>   * sorted list of clock divider, register value pairs
>   * taken from table 26-5, p.26-9, Freescale i.MX
> @@ -304,6 +321,11 @@ static const struct platform_device_id imx_i2c_devtype[] = {
>  };
>  MODULE_DEVICE_TABLE(platform, imx_i2c_devtype);
>  
> +static const struct of_device_id guts_device_ids[] = {
> +	{ .compatible = "fsl,qoriq-device-config", },
> +	{}
> +};
> +
>  static const struct of_device_id i2c_imx_dt_ids[] = {
>  	{ .compatible = "fsl,imx1-i2c", .data = &imx1_i2c_hwdata, },
>  	{ .compatible = "fsl,imx21-i2c", .data = &imx21_i2c_hwdata, },
> @@ -533,6 +555,9 @@ static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
>  	unsigned int div;
>  	int i;
>  
> +	if (!i2c_ipgclk_sel)
> +		i2c_clk_rate = i2c_clk_rate / 2;

It would be nice to have the variable inverted. You wouldn't have to
initialize a global variable with something else but 0 then.

> +
>  	/* Divider value calculation */
>  	if (i2c_imx->cur_clk == i2c_clk_rate)
>  		return;
> @@ -551,6 +576,10 @@ static void i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
>  	/* Store divider value */
>  	i2c_imx->ifdr = i2c_clk_div[i].val;
>  
> +	pr_alert("[%s] CLK Rate=%u Bitrate =%u Div =%u Value =%d\n",
> +		 __func__, i2c_clk_rate, i2c_imx->bitrate,
> +		 div, i2c_clk_div[i].val);

Please drop your debugging aids, for sure they shouldn't be pr_alert.

> +
>  	/*
>  	 * There dummy delay is calculated.
>  	 * It should be about one I2C clock period long.
> @@ -1116,6 +1145,9 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	int irq, ret;
>  	dma_addr_t phy_addr;
>  	u32 mul_value;
> +	struct device_node *guts_node;
> +	static struct ccsr_guts __iomem *guts_regs;
> +	u32 rcw_reg;
>  
>  	dev_dbg(&pdev->dev, "<%s>\n", __func__);
>  
> @@ -1135,6 +1167,38 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	if (!i2c_imx)
>  		return -ENOMEM;
>  
> +	if (soc_device_match(ls1046a_soc)) {
> +		/*
> +		 * Make device node for GUTS/DCFG (global utilities block)
> +		 * to read RCW.
> +		 */
> +		guts_node = of_find_matching_node(NULL, guts_device_ids);
> +		if (!guts_node) {
> +			dev_err(&pdev->dev, "Could not find GUTS node\n");
> +			return -ENODEV;
> +		}
> +		/*
> +		 * Memory (IO)  MAP the DCFG registers(for RCW) to
> +		 * be used in kernel virtual address space.
> +		 */
> +		guts_regs = of_iomap(guts_node, 0);
> +		of_node_put(guts_node);
> +		if (!guts_regs) {
> +			dev_err(&pdev->dev, "IOREMAP of GUTS node failed\n");
> +			return -ENOMEM;
> +		}
> +		/* Read rcw bit 424 (starting from 0) */
> +		rcw_reg = ioread32be(&guts_regs->rcwsr[RCW_I2C_IPGCLK_WORD]);
> +		pr_alert("RCW REG[%d]=0x%x\n", RCW_I2C_IPGCLK_WORD, rcw_reg);
> +		if (rcw_reg & RCW_I2C_IPGCLK_MASK) {
> +			pr_alert("Div by 2 Case Detected in RCW\n");
> +			i2c_ipgclk_sel = 1;
> +		} else {
> +			pr_alert("Div by 4 Case Detected in RCW\n");
> +			i2c_ipgclk_sel = 0;
> +		}
> +	}

This is done once per i2c controller, but it sets a variable valid for
all controllers. Either execute this code once outside of device
specific context or use a variable in driver data and not a global one.

Sascha

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