Re: [PATCH] drm/sun4i: hdmi: Implement I2C adapter for A10s DDC bus

From: Jonathan Liu
Date: Mon Jun 12 2017 - 01:47:52 EST

Hi Chen-Yu,

On 12 June 2017 at 13:28, Chen-Yu Tsai <wens@xxxxxxxx> wrote:
> On Mon, Jun 12, 2017 at 10:12 AM, Jonathan Liu <net147@xxxxxxxxx> wrote:
>> The drm_get_edid function should be used instead of drm_do_get_edid by
>> exposing the DDC bus as an I2C adapter. Implement this for A10s.
>
> Nice!

It is my first Linux kernel driver so there may be other things I have
overlooked. I am not sure about the behaviour of I2C writes larger
than 16 bytes but the EEPROMs I have tested only have a write buffer
of 8 bytes so writes are limited to a maximum of 8 bytes at a time
anyway.

>
>>
>> Signed-off-by: Jonathan Liu <net147@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/sun4i/Makefile | 1 +
>> drivers/gpu/drm/sun4i/sun4i_hdmi.h | 11 ++-
>> drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c | 96 +++----------------
>> drivers/gpu/drm/sun4i/sun4i_hdmi_i2c.c | 166 +++++++++++++++++++++++++++++++++
>> 4 files changed, 190 insertions(+), 84 deletions(-)
>> create mode 100644 drivers/gpu/drm/sun4i/sun4i_hdmi_i2c.c
>>
>> diff --git a/drivers/gpu/drm/sun4i/Makefile b/drivers/gpu/drm/sun4i/Makefile
>> index e29fd3a2ba9c..43c753cafc88 100644
>> --- a/drivers/gpu/drm/sun4i/Makefile
>> +++ b/drivers/gpu/drm/sun4i/Makefile
>> @@ -2,6 +2,7 @@ sun4i-drm-y += sun4i_drv.o
>> sun4i-drm-y += sun4i_framebuffer.o
>>
>> sun4i-drm-hdmi-y += sun4i_hdmi_enc.o
>> +sun4i-drm-hdmi-y += sun4i_hdmi_i2c.o
>> sun4i-drm-hdmi-y += sun4i_hdmi_ddc_clk.o
>> sun4i-drm-hdmi-y += sun4i_hdmi_tmds_clk.o
>>
>> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi.h b/drivers/gpu/drm/sun4i/sun4i_hdmi.h
>> index 2589bc92be59..8e7a70f67f04 100644
>> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi.h
>> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi.h
>> @@ -100,6 +100,7 @@
>> #define SUN4I_HDMI_DDC_CTRL_START_CMD BIT(30)
>> #define SUN4I_HDMI_DDC_CTRL_FIFO_DIR_MASK BIT(8)
>> #define SUN4I_HDMI_DDC_CTRL_FIFO_DIR_READ (0 << 8)
>> +#define SUN4I_HDMI_DDC_CTRL_FIFO_DIR_WRITE (1 << 8)
>> #define SUN4I_HDMI_DDC_CTRL_RESET BIT(0)
>>
>> #define SUN4I_HDMI_DDC_ADDR_REG 0x504
>> @@ -108,6 +109,10 @@
>> #define SUN4I_HDMI_DDC_ADDR_OFFSET(off) (((off) & 0xff) << 8)
>> #define SUN4I_HDMI_DDC_ADDR_SLAVE(addr) ((addr) & 0xff)
>>
>> +#define SUN4I_HDMI_DDC_INTERRUPT_STATUS_REG 0x50c
>> +#define SUN4I_HDMI_DDC_INTERRUPT_STATUS_FIFO_REQUEST BIT(4)
>> +#define SUN4I_HDMI_DDC_INTERRUPT_STATUS_TRANSFER_COMPLETE BIT(0)
>> +
>> #define SUN4I_HDMI_DDC_FIFO_CTRL_REG 0x510
>> #define SUN4I_HDMI_DDC_FIFO_CTRL_CLEAR BIT(31)
>>
>> @@ -115,7 +120,8 @@
>> #define SUN4I_HDMI_DDC_BYTE_COUNT_REG 0x51c
>>
>> #define SUN4I_HDMI_DDC_CMD_REG 0x520
>> -#define SUN4I_HDMI_DDC_CMD_EXPLICIT_EDDC_READ 6
>> +#define SUN4I_HDMI_DDC_CMD_IMPLICIT_WRITE 3
>> +#define SUN4I_HDMI_DDC_CMD_IMPLICIT_READ 5
>>
>> #define SUN4I_HDMI_DDC_CLK_REG 0x528
>> #define SUN4I_HDMI_DDC_CLK_M(m) (((m) & 0x7) << 3)
>> @@ -181,6 +187,8 @@ struct sun4i_hdmi {
>> struct clk *ddc_clk;
>> struct clk *tmds_clk;
>>
>> + struct i2c_adapter *i2c;
>> +
>> struct sun4i_drv *drv;
>>
>> bool hdmi_monitor;
>> @@ -192,5 +200,6 @@ int sun4i_ddc_create(struct sun4i_hdmi *hdmi, struct clk *clk);
>> int sun6i_ddc_create(struct sun4i_hdmi *hdmi, struct clk *clk);
>> int sun4i_tmds_create(struct sun4i_hdmi *hdmi);
>> int sun6i_tmds_create(struct sun4i_hdmi *hdmi);
>> +int sun4i_hdmi_i2c_create(struct sun4i_hdmi *hdmi);
>
> However you seem to have based it on the wrong branch/patches.
> You based them on my A31 HDMI patches, instead of what Maxime has
> in his sunxi-drm/for-next branch.
>
> I could add this to my A31 patches, though it probably won't make
> 4.13. Alternatively you could rebase them on top of Maxime's branch.

Yes, I forgot about that. I will rebase against sunxi-drm/for-next for V2.

>
>>
>> #endif /* _SUN4I_HDMI_H_ */
>> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
>> index e9abf93eb41c..6c9b11c4cf68 100644
>> --- a/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
>> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_enc.c
>> @@ -186,93 +186,13 @@ static const struct drm_encoder_funcs sun4i_hdmi_funcs = {
>> .destroy = drm_encoder_cleanup,
>> };
>>
>> -static int sun4i_hdmi_read_sub_block(struct sun4i_hdmi *hdmi,
>> - unsigned int blk, unsigned int offset,
>> - u8 *buf, unsigned int count)
>> -{
>> - unsigned long reg;
>> - int i;
>> -
>> - reg = readl(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> - reg &= ~SUN4I_HDMI_DDC_CTRL_FIFO_DIR_MASK;
>> - writel(reg | SUN4I_HDMI_DDC_CTRL_FIFO_DIR_READ,
>> - hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> -
>> - writel(SUN4I_HDMI_DDC_ADDR_SEGMENT(offset >> 8) |
>> - SUN4I_HDMI_DDC_ADDR_EDDC(DDC_SEGMENT_ADDR << 1) |
>> - SUN4I_HDMI_DDC_ADDR_OFFSET(offset) |
>> - SUN4I_HDMI_DDC_ADDR_SLAVE(DDC_ADDR),
>> - hdmi->base + SUN4I_HDMI_DDC_ADDR_REG);
>> -
>> - reg = readl(hdmi->base + SUN4I_HDMI_DDC_FIFO_CTRL_REG);
>> - writel(reg | SUN4I_HDMI_DDC_FIFO_CTRL_CLEAR,
>> - hdmi->base + SUN4I_HDMI_DDC_FIFO_CTRL_REG);
>> -
>> - writel(count, hdmi->base + SUN4I_HDMI_DDC_BYTE_COUNT_REG);
>> - writel(SUN4I_HDMI_DDC_CMD_EXPLICIT_EDDC_READ,
>> - hdmi->base + SUN4I_HDMI_DDC_CMD_REG);
>> -
>> - reg = readl(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> - writel(reg | SUN4I_HDMI_DDC_CTRL_START_CMD,
>> - hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> -
>> - if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG, reg,
>> - !(reg & SUN4I_HDMI_DDC_CTRL_START_CMD),
>> - 100, 100000))
>> - return -EIO;
>> -
>> - for (i = 0; i < count; i++)
>> - buf[i] = readb(hdmi->base + SUN4I_HDMI_DDC_FIFO_DATA_REG);
>> -
>> - return 0;
>> -}
>> -
>> -static int sun4i_hdmi_read_edid_block(void *data, u8 *buf, unsigned int blk,
>> - size_t length)
>> -{
>> - struct sun4i_hdmi *hdmi = data;
>> - int retry = 2, i;
>> -
>> - do {
>> - for (i = 0; i < length; i += SUN4I_HDMI_DDC_FIFO_SIZE) {
>> - unsigned char offset = blk * EDID_LENGTH + i;
>> - unsigned int count = min((unsigned int)SUN4I_HDMI_DDC_FIFO_SIZE,
>> - length - i);
>> - int ret;
>> -
>> - ret = sun4i_hdmi_read_sub_block(hdmi, blk, offset,
>> - buf + i, count);
>> - if (ret)
>> - return ret;
>> - }
>> - } while (!drm_edid_block_valid(buf, blk, true, NULL) && (retry--));
>> -
>> - return 0;
>> -}
>> -
>> static int sun4i_hdmi_get_modes(struct drm_connector *connector)
>> {
>> struct sun4i_hdmi *hdmi = drm_connector_to_sun4i_hdmi(connector);
>> - unsigned long reg;
>> struct edid *edid;
>> int ret;
>>
>> - /* Reset i2c controller */
>> - writel(SUN4I_HDMI_DDC_CTRL_ENABLE | SUN4I_HDMI_DDC_CTRL_RESET,
>> - hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> - if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG, reg,
>> - !(reg & SUN4I_HDMI_DDC_CTRL_RESET),
>> - 100, 2000))
>> - return -EIO;
>> -
>> - writel(SUN4I_HDMI_DDC_LINE_CTRL_SDA_ENABLE |
>> - SUN4I_HDMI_DDC_LINE_CTRL_SCL_ENABLE,
>> - hdmi->base + SUN4I_HDMI_DDC_LINE_CTRL_REG);
>> -
>> - clk_prepare_enable(hdmi->ddc_clk);
>> - clk_set_rate(hdmi->ddc_clk, 100000);
>> -
>> - edid = drm_do_get_edid(connector, sun4i_hdmi_read_edid_block, hdmi);
>> + edid = drm_get_edid(connector, hdmi->i2c);
>> if (!edid)
>> return 0;
>>
>> @@ -284,8 +204,6 @@ static int sun4i_hdmi_get_modes(struct drm_connector *connector)
>> ret = drm_add_edid_modes(connector, edid);
>> kfree(edid);
>>
>> - clk_disable_unprepare(hdmi->ddc_clk);
>> -
>> return ret;
>> }
>>
>> @@ -424,6 +342,7 @@ struct sun4i_hdmi_variant {
>> const struct drm_connector_helper_funcs *connector_helpers;
>> int (*ddc_create)(struct sun4i_hdmi *hdmi, struct clk *clk);
>> int (*tmds_create)(struct sun4i_hdmi *hdmi);
>> + int (*hdmi_i2c_create)(struct sun4i_hdmi *hdmi);
>> bool has_ddc_parent_clk;
>> bool has_reset_control;
>>
>> @@ -439,6 +358,7 @@ static const struct sun4i_hdmi_variant sun5i_variant = {
>> .connector_helpers = &sun4i_hdmi_connector_helper_funcs,
>> .ddc_create = sun4i_ddc_create,
>> .tmds_create = sun4i_tmds_create,
>> + .hdmi_i2c_create = sun4i_hdmi_i2c_create,
>> .has_ddc_parent_clk = false,
>> .has_reset_control = false,
>> .pad_ctrl0_init_val = SUN4I_HDMI_PAD_CTRL0_TXEN |
>> @@ -622,6 +542,14 @@ static int sun4i_hdmi_bind(struct device *dev, struct device *master,
>> goto err_disable_mod_clk;
>> }
>>
>> + if (hdmi->variant->hdmi_i2c_create) {
>
> I don't think this would be optional.

This will be addressed in V2 when the patch is rebased.

>
>> + ret = hdmi->variant->hdmi_i2c_create(hdmi);
>> + if (ret) {
>> + dev_err(dev, "Couldn't create the HDMI I2C adapter\n");
>> + goto err_disable_mod_clk;
>> + }
>> + }
>> +
>
> You should also fix up the error path so that the I2C adapter
> gets remove if any of the subsequent calls fail.
>
>> drm_encoder_helper_add(&hdmi->encoder,
>> &sun4i_hdmi_helper_funcs);
>> ret = drm_encoder_init(drm,
>> @@ -676,6 +604,8 @@ static void sun4i_hdmi_unbind(struct device *dev, struct device *master,
>>
>> drm_connector_cleanup(&hdmi->connector);
>> drm_encoder_cleanup(&hdmi->encoder);
>> + if (hdmi->i2c)
>> + i2c_del_adapter(hdmi->i2c);
>
> So neither should this be optional.

Ditto. This will be addressed in V2 when the patch is rebased.

>
>> clk_disable_unprepare(hdmi->mod_clk);
>> clk_disable_unprepare(hdmi->bus_clk);
>> }
>> diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_i2c.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_i2c.c
>> new file mode 100644
>> index 000000000000..c33fa13cc668
>> --- /dev/null
>> +++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_i2c.c
>> @@ -0,0 +1,166 @@
>> +/*
>> + * Copyright (C) 2017 Jonathan Liu
>> + *
>> + * Jonathan Liu <net147@xxxxxxxxx>
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License as
>> + * published by the Free Software Foundation; either version 2 of
>> + * the License, or (at your option) any later version.
>> + */
>> +
>> +#include <linux/init.h>
>> +#include <linux/module.h>
>> +#include <linux/errno.h>
>> +#include <linux/clk.h>
>> +#include <linux/i2c.h>
>> +#include <linux/iopoll.h>
>> +
>> +#include "sun4i_hdmi.h"
>> +
>> +static int xfer_msg_chunk(struct sun4i_hdmi *hdmi, struct i2c_msg *msg)
>> +{
>> + u32 count = min_t(u32, msg->len, SUN4I_HDMI_DDC_FIFO_SIZE);
>> + u32 reg;
>> + int i;
>> +
>> + reg = readl(hdmi->base + SUN4I_HDMI_DDC_FIFO_CTRL_REG);
>> + writel(reg | SUN4I_HDMI_DDC_FIFO_CTRL_CLEAR,
>> + hdmi->base + SUN4I_HDMI_DDC_FIFO_CTRL_REG);
>> +
>> + writel(count, hdmi->base
>> + + SUN4I_HDMI_DDC_BYTE_COUNT_REG);
>> + writel(msg->flags & I2C_M_RD
>> + ? SUN4I_HDMI_DDC_CMD_IMPLICIT_READ
>> + : SUN4I_HDMI_DDC_CMD_IMPLICIT_WRITE,
>> + hdmi->base + SUN4I_HDMI_DDC_CMD_REG);
>> +
>> + reg = readl(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> + writel(reg | SUN4I_HDMI_DDC_CTRL_START_CMD,
>> + hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> +
>> + if (!(msg->flags & I2C_M_RD)) {
>> + for (i = 0; i < count; i++) {
>> + writeb(*msg->buf++, hdmi->base
>> + + SUN4I_HDMI_DDC_FIFO_DATA_REG);
>> + --msg->len;
>> + }
>> + }
>> +
>> + if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG,
>> + reg,
>> + !(reg & SUN4I_HDMI_DDC_CTRL_START_CMD),
>> + 100, 100000))
>> + return -EIO;
>> +
>> + reg = readl(hdmi->base + SUN4I_HDMI_DDC_INTERRUPT_STATUS_REG);
>> + reg &= ~SUN4I_HDMI_DDC_INTERRUPT_STATUS_FIFO_REQUEST;
>> +
>> + if (reg != SUN4I_HDMI_DDC_INTERRUPT_STATUS_TRANSFER_COMPLETE)
>> + return -EIO;
>> +
>> + if (msg->flags & I2C_M_RD) {
>> + for (i = 0; i < count; i++) {
>> + *msg->buf++ = readb(hdmi->base
>> + + SUN4I_HDMI_DDC_FIFO_DATA_REG);
>> + --msg->len;
>> + }
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int xfer_msg(struct sun4i_hdmi *hdmi, struct i2c_msg *msg)
>> +{
>> + u32 reg;
>> + int ret;
>> +
>> + if (!msg->len)
>> + return -EIO;
>> +
>> + while (msg->len) {
>> + reg = readl(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> + reg &= ~SUN4I_HDMI_DDC_CTRL_FIFO_DIR_MASK;
>> +
>> + writel(reg | (msg->flags & I2C_M_RD
>> + ? SUN4I_HDMI_DDC_CTRL_FIFO_DIR_READ
>> + : SUN4I_HDMI_DDC_CTRL_FIFO_DIR_WRITE),
>> + hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> +
>> + writel(SUN4I_HDMI_DDC_ADDR_SLAVE(msg->addr),
>> + hdmi->base + SUN4I_HDMI_DDC_ADDR_REG);
>> +
>> + ret = xfer_msg_chunk(hdmi, msg);
>> + if (ret)
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int sun4i_hdmi_i2c_xfer(struct i2c_adapter *adap,
>> + struct i2c_msg *msgs, int num)
>> +{
>> + struct sun4i_hdmi *hdmi = i2c_get_adapdata(adap);
>> + u32 reg;
>> + int err, ret = num;
>> + int i;
>> +
>> + /* Reset i2c controller */
>> + writel(SUN4I_HDMI_DDC_CTRL_ENABLE | SUN4I_HDMI_DDC_CTRL_RESET,
>> + hdmi->base + SUN4I_HDMI_DDC_CTRL_REG);
>> + if (readl_poll_timeout(hdmi->base + SUN4I_HDMI_DDC_CTRL_REG, reg,
>> + !(reg & SUN4I_HDMI_DDC_CTRL_RESET),
>> + 100, 2000))
>> + return -EIO;
>> +
>> + writel(SUN4I_HDMI_DDC_LINE_CTRL_SDA_ENABLE |
>> + SUN4I_HDMI_DDC_LINE_CTRL_SCL_ENABLE,
>> + hdmi->base + SUN4I_HDMI_DDC_LINE_CTRL_REG);
>> +
>> + clk_prepare_enable(hdmi->ddc_clk);
>> + clk_set_rate(hdmi->ddc_clk, 100000);
>> +
>> + for (i = 0; i < num; i++) {
>> + err = xfer_msg(hdmi, &msgs[i]);
>> + if (err) {
>> + ret = err;
>> + break;
>> + }
>> + }
>> +
>> + clk_disable_unprepare(hdmi->ddc_clk);
>> + return ret;
>> +}
>> +
>> +static u32 sun4i_hdmi_i2c_func(struct i2c_adapter *adap)
>> +{
>> + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
>> +}
>> +
>> +static const struct i2c_algorithm sun4i_hdmi_i2c_algorithm = {
>> + .master_xfer = sun4i_hdmi_i2c_xfer,
>> + .functionality = sun4i_hdmi_i2c_func,
>> +};
>> +
>> +static struct i2c_adapter sun4i_hdmi_i2c_adapter = {
>> + .owner = THIS_MODULE,
>> + .class = I2C_CLASS_DDC,
>> + .algo = &sun4i_hdmi_i2c_algorithm,
>> + .name = "sun4i_hdmi_i2c adapter",
>> +};
>> +
>> +int sun4i_hdmi_i2c_create(struct sun4i_hdmi *hdmi)
>> +{
>> + int ret = 0;
>> +
>> + i2c_set_adapdata(&sun4i_hdmi_i2c_adapter, hdmi);
>> +
>> + ret = i2c_add_adapter(&sun4i_hdmi_i2c_adapter);
>> + if (ret)
>> + return ret;
>> +
>> + hdmi->i2c = &sun4i_hdmi_i2c_adapter;
>> +
>> + return ret;
>> +}
>> --
>> 2.12.2
>>
>
> The rest looks good to me.
>
> Regards
> ChenYu

Will follow up with V2 shortly.

Regards,
Jonathan