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Message-ID: <cee77d68-262e-e39b-bab4-a3bfbd1de6fe@kali.org>
Date: Wed, 30 Sep 2020 18:07:09 -0500
From: Steev Klimaszewski <steev@...i.org>
To: Bjorn Andersson <bjorn.andersson@...aro.org>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Rob Herring <robh+dt@...nel.org>,
Andrzej Hajda <a.hajda@...sung.com>,
Neil Armstrong <narmstrong@...libre.com>,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
Jonas Karlman <jonas@...boo.se>,
Jernej Skrabec <jernej.skrabec@...l.net>,
Douglas Anderson <dianders@...omium.org>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/bridge: ti-sn65dsi86: Expose backlight controls
On 9/30/20 5:35 PM, Bjorn Andersson wrote:
> The TI SN65DSI86 can be configured to generate a PWM pulse on GPIO4,
> to be used to drive a backlight driver.
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
> drivers/gpu/drm/bridge/Kconfig | 1 +
> drivers/gpu/drm/bridge/ti-sn65dsi86.c | 143 +++++++++++++++++++++++++-
> 2 files changed, 140 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index 43271c21d3fc..eea310bd88e1 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -195,6 +195,7 @@ config DRM_TI_SN65DSI86
> select REGMAP_I2C
> select DRM_PANEL
> select DRM_MIPI_DSI
> + select BACKLIGHT_CLASS_DEVICE
> help
> Texas Instruments SN65DSI86 DSI to eDP Bridge driver
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index 5b6e19ecbc84..41e24d0dbd18 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -68,6 +68,7 @@
> #define SN_GPIO_MUX_OUTPUT 1
> #define SN_GPIO_MUX_SPECIAL 2
> #define SN_GPIO_MUX_MASK 0x3
> +#define SN_GPIO_MUX_SHIFT(gpio) ((gpio) * 2)
> #define SN_AUX_WDATA_REG(x) (0x64 + (x))
> #define SN_AUX_ADDR_19_16_REG 0x74
> #define SN_AUX_ADDR_15_8_REG 0x75
> @@ -86,6 +87,12 @@
> #define SN_ML_TX_MODE_REG 0x96
> #define ML_TX_MAIN_LINK_OFF 0
> #define ML_TX_NORMAL_MODE BIT(0)
> +#define SN_PWM_PRE_DIV_REG 0xA0
> +#define SN_BACKLIGHT_SCALE_REG 0xA1
> +#define SN_BACKLIGHT_REG 0xA3
> +#define SN_PWM_CTL_REG 0xA5
> +#define SN_PWM_ENABLE BIT(1)
> +#define SN_PWM_INVERT BIT(0)
> #define SN_AUX_CMD_STATUS_REG 0xF4
> #define AUX_IRQ_STATUS_AUX_RPLY_TOUT BIT(3)
> #define AUX_IRQ_STATUS_AUX_SHORT BIT(5)
> @@ -155,6 +162,8 @@ struct ti_sn_bridge {
> struct gpio_chip gchip;
> DECLARE_BITMAP(gchip_output, SN_NUM_GPIOS);
> #endif
> + u32 brightness;
> + u32 max_brightness;
> };
>
> static const struct regmap_range ti_sn_bridge_volatile_ranges[] = {
> @@ -173,6 +182,18 @@ static const struct regmap_config ti_sn_bridge_regmap_config = {
> .cache_type = REGCACHE_NONE,
> };
>
> +static void ti_sn_bridge_read_u16(struct ti_sn_bridge *pdata,
> + unsigned int reg, u16 *val)
> +{
> + unsigned int high;
> + unsigned int low;
> +
> + regmap_read(pdata->regmap, reg, &low);
> + regmap_read(pdata->regmap, reg + 1, &high);
> +
> + *val = high << 8 | low;
> +}
> +
> static void ti_sn_bridge_write_u16(struct ti_sn_bridge *pdata,
> unsigned int reg, u16 val)
> {
> @@ -180,6 +201,50 @@ static void ti_sn_bridge_write_u16(struct ti_sn_bridge *pdata,
> regmap_write(pdata->regmap, reg + 1, val >> 8);
> }
>
> +static int ti_sn_backlight_update(struct ti_sn_bridge *pdata)
> +{
> + unsigned int pre_div;
> +
> + if (!pdata->max_brightness)
> + return 0;
> +
> + /* Enable PWM on GPIO4 */
> + regmap_update_bits(pdata->regmap, SN_GPIO_CTRL_REG,
> + SN_GPIO_MUX_MASK << SN_GPIO_MUX_SHIFT(4 - 1),
> + SN_GPIO_MUX_SPECIAL << SN_GPIO_MUX_SHIFT(4 - 1));
> +
> + if (pdata->brightness) {
> + /* Set max brightness */
> + ti_sn_bridge_write_u16(pdata, SN_BACKLIGHT_SCALE_REG, pdata->max_brightness);
> +
> + /* Set brightness */
> + ti_sn_bridge_write_u16(pdata, SN_BACKLIGHT_REG, pdata->brightness);
> +
> + /*
> + * The PWM frequency is derived from the refclk as:
> + * PWM_FREQ = REFCLK_FREQ / (PWM_PRE_DIV * BACKLIGHT_SCALE + 1)
> + *
> + * A hand wavy estimate based on 12MHz refclk and 500Hz desired
> + * PWM frequency gives us a pre_div resulting in a PWM
> + * frequency of between 500 and 1600Hz, depending on the actual
> + * refclk rate.
> + *
> + * One is added to avoid high BACKLIGHT_SCALE values to produce
> + * a pre_div of 0 - which cancels out the large BACKLIGHT_SCALE
> + * value.
> + */
> + pre_div = 12000000 / (500 * pdata->max_brightness) + 1;
> + regmap_write(pdata->regmap, SN_PWM_PRE_DIV_REG, pre_div);
> +
> + /* Enable PWM */
> + regmap_update_bits(pdata->regmap, SN_PWM_CTL_REG, SN_PWM_ENABLE, SN_PWM_ENABLE);
> + } else {
> + regmap_update_bits(pdata->regmap, SN_PWM_CTL_REG, SN_PWM_ENABLE, 0);
> + }
> +
> + return 0;
> +}
> +
> static int __maybe_unused ti_sn_bridge_resume(struct device *dev)
> {
> struct ti_sn_bridge *pdata = dev_get_drvdata(dev);
> @@ -193,7 +258,7 @@ static int __maybe_unused ti_sn_bridge_resume(struct device *dev)
>
> gpiod_set_value(pdata->enable_gpio, 1);
>
> - return ret;
> + return ti_sn_backlight_update(pdata);
> }
>
> static int __maybe_unused ti_sn_bridge_suspend(struct device *dev)
> @@ -1010,7 +1075,7 @@ static int ti_sn_bridge_gpio_direction_input(struct gpio_chip *chip,
> unsigned int offset)
> {
> struct ti_sn_bridge *pdata = gpiochip_get_data(chip);
> - int shift = offset * 2;
> + int shift = SN_GPIO_MUX_SHIFT(offset);
> int ret;
>
> if (!test_and_clear_bit(offset, pdata->gchip_output))
> @@ -1038,7 +1103,7 @@ static int ti_sn_bridge_gpio_direction_output(struct gpio_chip *chip,
> unsigned int offset, int val)
> {
> struct ti_sn_bridge *pdata = gpiochip_get_data(chip);
> - int shift = offset * 2;
> + int shift = SN_GPIO_MUX_SHIFT(offset);
> int ret;
>
> if (test_and_set_bit(offset, pdata->gchip_output))
> @@ -1073,12 +1138,17 @@ static const char * const ti_sn_bridge_gpio_names[SN_NUM_GPIOS] = {
>
> static int ti_sn_setup_gpio_controller(struct ti_sn_bridge *pdata)
> {
> + int ngpio = SN_NUM_GPIOS;
> int ret;
>
> /* Only init if someone is going to use us as a GPIO controller */
> if (!of_property_read_bool(pdata->dev->of_node, "gpio-controller"))
> return 0;
>
> + /* If GPIO4 is used for backlight, reduce number of gpios */
> + if (pdata->max_brightness)
> + ngpio--;
> +
> pdata->gchip.label = dev_name(pdata->dev);
> pdata->gchip.parent = pdata->dev;
> pdata->gchip.owner = THIS_MODULE;
> @@ -1092,7 +1162,7 @@ static int ti_sn_setup_gpio_controller(struct ti_sn_bridge *pdata)
> pdata->gchip.set = ti_sn_bridge_gpio_set;
> pdata->gchip.can_sleep = true;
> pdata->gchip.names = ti_sn_bridge_gpio_names;
> - pdata->gchip.ngpio = SN_NUM_GPIOS;
> + pdata->gchip.ngpio = ngpio;
> pdata->gchip.base = -1;
> ret = devm_gpiochip_add_data(pdata->dev, &pdata->gchip, pdata);
> if (ret)
> @@ -1159,6 +1229,65 @@ static void ti_sn_bridge_parse_lanes(struct ti_sn_bridge *pdata,
> pdata->ln_polrs = ln_polrs;
> }
>
> +static int ti_sn_backlight_update_status(struct backlight_device *bl)
> +{
> + struct ti_sn_bridge *pdata = bl_get_data(bl);
> + int brightness = bl->props.brightness;
> +
> + if (bl->props.power != FB_BLANK_UNBLANK ||
> + bl->props.fb_blank != FB_BLANK_UNBLANK ||
> + bl->props.state & BL_CORE_FBBLANK) {
> + pdata->brightness = 0;
> + }
> +
> + pdata->brightness = brightness;
> +
> + return ti_sn_backlight_update(pdata);
> +}
> +
> +static int ti_sn_backlight_get_brightness(struct backlight_device *bl)
> +{
> + struct ti_sn_bridge *pdata = bl_get_data(bl);
> + u16 val;
> +
> + ti_sn_bridge_read_u16(pdata, SN_BACKLIGHT_REG, &val);
> +
> + return val;
> +}
> +
> +const struct backlight_ops ti_sn_backlight_ops = {
> + .update_status = ti_sn_backlight_update_status,
> + .get_brightness = ti_sn_backlight_get_brightness,
> +};
> +
> +static int ti_sn_backlight_init(struct ti_sn_bridge *pdata)
> +{
> + struct backlight_properties props = {};
> + struct backlight_device *bl;
> + struct device *dev = pdata->dev;
> + struct device_node *np = dev->of_node;
> + int ret;
> +
> + ret = of_property_read_u32(np, "ti,backlight-scale", &pdata->max_brightness);
> + if (ret == -EINVAL) {
> + return 0;
> + } else if (ret || pdata->max_brightness >= 0xffff) {
> + DRM_ERROR("invalid max-brightness\n");
> + return -EINVAL;
> + }
> +
> + props.type = BACKLIGHT_RAW;
> + props.max_brightness = pdata->max_brightness;
> + bl = devm_backlight_device_register(dev, "sn65dsi86", dev, pdata,
> + &ti_sn_backlight_ops, &props);
> + if (IS_ERR(bl)) {
> + DRM_ERROR("failed to register backlight device\n");
> + return PTR_ERR(bl);
> + }
> +
> + return 0;
> +}
> +
> static int ti_sn_bridge_probe(struct i2c_client *client,
> const struct i2c_device_id *id)
> {
> @@ -1224,6 +1353,12 @@ static int ti_sn_bridge_probe(struct i2c_client *client,
>
> pm_runtime_enable(pdata->dev);
>
> + ret = ti_sn_backlight_init(pdata);
> + if (ret) {
> + pm_runtime_disable(pdata->dev);
> + return ret;
> + }
> +
> ret = ti_sn_setup_gpio_controller(pdata);
> if (ret) {
> pm_runtime_disable(pdata->dev);
Tested-By: Steev Klimaszewski <steev@...i.org>
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