Message-ID: <20210128094258.000012c3@gmail.com>
Date:   Thu, 28 Jan 2021 09:42:58 +0800
From:   carlis <zhangxuezhi3@...il.com>
To:     Kari Argillander <kari.argillander@...il.com>
Cc:     gregkh@...uxfoundation.org, colin.king@...onical.com,
        oliver.graute@...oconnector.com, zhangxuezhi1@...ong.com,
        mh12gx2825@...il.com, sbrivio@...hat.com,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10] staging: fbtft: add tearing signal detect

On Thu, 28 Jan 2021 00:32:22 +0200
Kari Argillander <kari.argillander@...il.com> wrote:

> 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?
> 
OK,i will fix it in patch v12 tomorrow

> >  #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 ;
hi, i have fix it in the patch v11
> 
> > +static struct completion spi_panel_te;  
> 
> What if multiple displays? Is this possible for user?
I will check it carefully again about this logic.
> 
> > +
> > +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.
You mean i just delete this dev_err print ?!
like this:
	par->gpio.te = devm_gpiod_get_index_optional(dev, "te",
0,GPIOD_IN); 
        if (IS_ERR(par->gpio.te))
		return PTR_ERR(par->gpio.te);
> 
> > +	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?
i will fix it in patch v12 tomorrow
> 
> > +	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.
i will fix it in patch v12 tomorrow
> > +/* 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.
> 
hi, i copy fbtft_write_vmem16_bus8 from file fbtft_bus.c and modify it
,just add te wait logic, i will take more time to check this original
function.
> > +}
> > +
> >  /**
> >   * 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
> >   

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