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Date:   Thu, 28 Jan 2021 00:32:22 +0200
From:   Kari Argillander <kari.argillander@gmail.com>
To:     Carlis <zhangxuezhi3@gmail.com>
Cc:     gregkh@linuxfoundation.org, colin.king@canonical.com,
        oliver.graute@kococonnector.com, zhangxuezhi1@yulong.com,
        mh12gx2825@gmail.com, sbrivio@redhat.com,
        dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
        devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10] staging: fbtft: add tearing signal detect
Message-ID: <20210127223222.3lavtl3roc4cabso@kari-VirtualBox>
References: <1611754972-151016-1-git-send-email-zhangxuezhi3@gmail.com>
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In-Reply-To: <1611754972-151016-1-git-send-email-zhangxuezhi3@gmail.com>
Precedence: bulk

On Wed, Jan 27, 2021 at 09:42:52PM +0800, Carlis wrote:
> For st7789v ic,when we need continuous full screen refresh, it is best to
> wait for the TE signal arrive to avoid screen tearing
 
> diff --git a/drivers/staging/fbtft/fb_st7789v.c b/drivers/staging/fbtft/fb_st7789v.c
> index 3a280cc..cba08a8 100644
> --- a/drivers/staging/fbtft/fb_st7789v.c
> +++ b/drivers/staging/fbtft/fb_st7789v.c
> @@ -9,9 +9,12 @@
>  #include <linux/delay.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
> +#include <linux/mutex.h>
> +#include <linux/interrupt.h>
> +#include <linux/completion.h>
>  #include <linux/module.h>
>  #include <video/mipi_display.h>
> -
> +#include <linux/gpio/consumer.h>

Space after local headers. Also this should one up so all Linux headers
are group together. You agreed?

>  #include "fbtft.h"
>  
>  #define DRVNAME "fb_st7789v"
> @@ -66,6 +69,32 @@ enum st7789v_command {
>  #define MADCTL_MX BIT(6) /* bitmask for column address order */
>  #define MADCTL_MY BIT(7) /* bitmask for page address order */
>  
> +#define SPI_PANEL_TE_TIMEOUT	400 /* msecs */
> +static struct mutex te_mutex;/* mutex for set te gpio irq status */

Space after ;

> +static struct completion spi_panel_te;

What if multiple displays? Is this possible for user?

> +
> +static irqreturn_t spi_panel_te_handler(int irq, void *data)
> +{
> +	complete(&spi_panel_te);
> +	return IRQ_HANDLED;
> +}
> +
> +static void set_spi_panel_te_irq_status(struct fbtft_par *par, bool enable)
> +{
> +	static int te_irq_count;

Same here. Maybe you can think better way and then this code would also be
cleaner.

> +
> +	mutex_lock(&te_mutex);

So locking should be done if we really do action and not just in case.

> +
> +	if (enable) {
> +		if (++te_irq_count == 1)
> +			enable_irq(gpiod_to_irq(par->gpio.te));
> +	} else {
> +		if (--te_irq_count == 0)
> +			disable_irq(gpiod_to_irq(par->gpio.te));
> +	}
> +	mutex_unlock(&te_mutex);
> +}
> +
>  /**
>   * init_display() - initialize the display controller
>   *
> @@ -82,6 +111,33 @@ enum st7789v_command {
>   */
>  static int init_display(struct fbtft_par *par)
>  {
> +	int rc;
> +	struct device *dev = par->info->device;
> +
> +	par->gpio.te = devm_gpiod_get_index_optional(dev, "te", 0, GPIOD_IN);
> +	if (IS_ERR(par->gpio.te)) {
> +		rc = PTR_ERR(par->gpio.te);
> +		dev_err(par->info->device, "Failed to request te gpio: %d\n", rc);
> +		return rc;
> +	}

You request with optinal and you still want to error out? We could just
continue and not care about that error. User will be happier if device
still works somehow.

> +	if (par->gpio.te) {
> +		init_completion(&spi_panel_te);
> +		mutex_init(&te_mutex);
> +		rc = devm_request_irq(dev,
> +				      gpiod_to_irq(par->gpio.te),
> +				     spi_panel_te_handler, IRQF_TRIGGER_RISING,
> +				     "TE_GPIO", par);
> +		if (rc) {
> +			dev_err(par->info->device, "TE request_irq failed.\n");
> +			devm_gpiod_put(dev, par->gpio.te);
> +			return rc;
> +		}
> +
> +		disable_irq_nosync(gpiod_to_irq(par->gpio.te));
> +	} else {
> +		dev_info(par->info->device, "%s:%d, TE gpio not specified\n",
> +			 __func__, __LINE__);
> +	}
>  	/* turn off sleep mode */
>  	write_reg(par, MIPI_DCS_EXIT_SLEEP_MODE);
>  	mdelay(120);
> @@ -137,6 +193,9 @@ static int init_display(struct fbtft_par *par)
>  	 */
>  	write_reg(par, PWCTRL1, 0xA4, 0xA1);
>  
> +    /*Tearing Effect Line On*/

Spaces and why upcase everything?

> +	if (par->gpio.te)
> +		write_reg(par, 0x35, 0x00);
>  	write_reg(par, MIPI_DCS_SET_DISPLAY_ON);
>  
>  	if (HSD20_IPS)
> @@ -145,6 +204,76 @@ static int init_display(struct fbtft_par *par)
>  	return 0;
>  }
>  
> +/*****************************************************************************
> + *
> + *   int (*write_vmem)(struct fbtft_par *par);
> + *
> + *****************************************************************************/
> +

Why this kind of function comment? Please use same as another function
comments in this file. They are atleast almoust like kernel-doc style.

> +/* 16 bit pixel over 8-bit databus */
> +static int st7789v_write_vmem16_bus8(struct fbtft_par *par, size_t offset, size_t len)
> +{
> +	u16 *vmem16;
> +	__be16 *txbuf16 = par->txbuf.buf;
> +	size_t remain;
> +	size_t to_copy;
> +	size_t tx_array_size;
> +	int i;
> +	int ret = 0;
> +	size_t startbyte_size = 0;
> +
> +	fbtft_par_dbg(DEBUG_WRITE_VMEM, par, "st7789v ---%s(offset=%zu, len=%zu)\n",
> +		      __func__, offset, len);
> +
> +	remain = len / 2;
> +	vmem16 = (u16 *)(par->info->screen_buffer + offset);
> +
> +	if (par->gpio.dc)
> +		gpiod_set_value(par->gpio.dc, 1);
> +
> +	/* non buffered write */
> +	if (!par->txbuf.buf)
> +		return par->fbtftops.write(par, vmem16, len);
> +
> +	/* buffered write */
> +	tx_array_size = par->txbuf.len / 2;
> +
> +	if (par->startbyte) {
> +		txbuf16 = par->txbuf.buf + 1;
> +		tx_array_size -= 2;
> +		*(u8 *)(par->txbuf.buf) = par->startbyte | 0x2;
> +		startbyte_size = 1;
> +	}
> +
> +	while (remain) {

for (remain = len / 2; remain; remain -= to_copy) {

or even use len = len / 2 if you wanna save variable.

> +		to_copy = min(tx_array_size, remain);

Care must be taken that this will not be endless loop if another is 0. I
will not check this further but hopefully you have.

> +		dev_dbg(par->info->device, "    to_copy=%zu, remain=%zu\n",
> +			to_copy, remain - to_copy);
> +
> +		for (i = 0; i < to_copy; i++)
> +			txbuf16[i] = cpu_to_be16(vmem16[i]);
> +
> +		vmem16 = vmem16 + to_copy;

+= Or you can ++ vmem16 at the for loop but that is not so readable
sometimes with pointers.

> +		if (par->gpio.te) {
> +			set_spi_panel_te_irq_status(par, true);
> +			reinit_completion(&spi_panel_te);
> +			ret = wait_for_completion_timeout(&spi_panel_te,
> +							  msecs_to_jiffies(SPI_PANEL_TE_TIMEOUT));
> +			if (ret == 0)

!ret

> +				dev_err(par->info->device, "wait panel TE time out\n");
> +		}
> +		ret = par->fbtftops.write(par, par->txbuf.buf,
> +					 startbyte_size + to_copy * 2);
> +		if (par->gpio.te)
> +			set_spi_panel_te_irq_status(par, false);
> +		if (ret < 0)
> +			return ret;
> +		remain -= to_copy;
> +	}
> +
> +	return ret;

Do we want to return something over 0? If not then this can be return 0.
And then you do not need to even init ret value at the beginning.

Also wait little bit like Greg sayd before sending new version. Someone
might nack about what I say or say something more.

> +}
> +
>  /**
>   * set_var() - apply LCD properties like rotation and BGR mode
>   *
> @@ -259,6 +388,7 @@ static int blank(struct fbtft_par *par, bool on)
>  	.gamma = HSD20_IPS_GAMMA,
>  	.fbtftops = {
>  		.init_display = init_display,
> +		.write_vmem = st7789v_write_vmem16_bus8,
>  		.set_var = set_var,
>  		.set_gamma = set_gamma,
>  		.blank = blank,
> diff --git a/drivers/staging/fbtft/fbtft.h b/drivers/staging/fbtft/fbtft.h
> index 76f8c09..93bac05 100644
> --- a/drivers/staging/fbtft/fbtft.h
> +++ b/drivers/staging/fbtft/fbtft.h
> @@ -212,6 +212,7 @@ struct fbtft_par {
>  		struct gpio_desc *wr;
>  		struct gpio_desc *latch;
>  		struct gpio_desc *cs;
> +		struct gpio_desc *te;
>  		struct gpio_desc *db[16];
>  		struct gpio_desc *led[16];
>  		struct gpio_desc *aux[16];
> -- 
> 1.9.1
>