[PATCH v12] staging: fbtft: add tearing signal detect
carlis
zhangxuezhi3 at gmail.com
Fri Jan 29 05:01:10 UTC 2021
On Thu, 28 Jan 2021 16:33:02 +0200
Andy Shevchenko <andy.shevchenko at gmail.com> wrote:
> On Thu, Jan 28, 2021 at 2:58 PM Carlis <zhangxuezhi3 at gmail.com> wrote:
>
> Thanks for your contribution, my comments below.
>
> > From: zhangxuezhi <zhangxuezhi1 at yulong.com>
>
> You probably have to configure your Git to use the same account for
> author and committer.
hi,you mean like below:
Carlis <zhangxuezhi1 at yulong.com>
?
>
> > For st7789v ic,when we need continuous full screen refresh, it is
> > best to
>
> 'ic,when' -> 'IC, when'
>
> > wait for the TE signal arrive to avoid screen tearing
>
> Decode TE for people who are not familiar with the abbreviation.
>
> Missed period at the end of sentence.
>
> ...
>
> > #include <linux/delay.h>
> > #include <linux/init.h>
> > #include <linux/kernel.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/completion.h>
> > #include <linux/module.h>
> > +#include <linux/gpio/consumer.h>
> > +
>
> Good, but I would rather squeeze it above to be more or less ordered,
> like just after delay.h inclusion.
>
> > #include <video/mipi_display.h>
>
> ...
>
> > +#define SPI_PANEL_TE_TIMEOUT 400 /* msecs */
>
> Useless comment. Instead use _MS suffix in the name of constant.
> Besides that please add a comment explaining why this value has been
> chosen.
>
> ...
>
> > +static struct completion spi_panel_te;
>
> As Greg said.
>
> ...
>
> > static int init_display(struct fbtft_par *par)
> > {
> > + int rc;
> > + struct device *dev = par->info->device;
>
> Keep reversed xmas tree order:
>
> struct device *dev = par->info->device;
> int rc;
>
> ...
>
> > + par->gpio.te = devm_gpiod_get_index_optional(dev, "te", 0,
> > GPIOD_IN);
>
> No need to have it requested for all time since you use it as an IRQ
> later on. The IRQ chip will call the GPIO library framework to lock a
> pin as IRQ anyway.
>
> > + if (IS_ERR(par->gpio.te))
> > + return dev_err_probe(par->info->device,
> > PTR_ERR(par->gpio.te),
> > + "Failed to request te
> > gpio\n");
>
> > + if (par->gpio.te) {
>
> Instead you should probably do the following:
>
> int irq;
>
> irq = gpiod_to_irq(...);
> if (irq > 0)
>
> > + init_completion(&spi_panel_te);
> > + rc = devm_request_irq(dev,
>
> > + gpiod_to_irq(par->gpio.te),
>
> ...and here simply use irq.
>
> > + spi_panel_te_handler,
> > IRQF_TRIGGER_RISING,
> > + "TE_GPIO", par);
>
> > + if (IS_ERR(rc))
>
> This is wrong. rc is integer no IS_ERR() is required. Ditto for
> PTR_ERR(). Have you even looked for these macros implementations?
>
> > + return dev_err_probe(par->info->device,
> > PTR_ERR(rc),
>
> Use your temporary variable and move...
>
> > + "TE request_irq
> > failed.\n");
>
> ...this on the previous line.
>
> > + disable_irq_nosync(gpiod_to_irq(par->gpio.te));
>
> Why do you call gpio_to_irq() twice?
>
>
> > + } else {
> > + dev_info(par->info->device, "%s:%d, TE gpio not
> > specified\n",
> > + __func__, __LINE__);
>
> Remove this noise (besides the fact that we don't use __file__ and
> __LINE__ in messages like this.
>
> > + }
>
> Taking all together you probably need to create a helper and use it
> inside init_display(), like
>
> static int init_tearing_effect_line(struct fbtft_par *par)
> {
> struct device *dev = par->info->device;
> struct gpio_desc *te;
> int irq, rc;
>
> te = gpiod_get_optional(dev, "te", GPIOD_IN);
> if (IS_ERR(te))
> return dev_err_probe(dev, PTR_ERR(te), "Failed to request
> te GPIO\n");
>
> irq = gpiod_to_irq(te); // this value you have to save in the
> driver's (per device) data structure.
>
> /* GPIO is locked as an IRQ, we may drop the reference */
> gpiod_put(te);
>
> init_completion(&spi_panel_te); // should be in the (per device)
> data structure
> rc = devm_request_irq(dev, irq, spi_panel_te_handler,
> IRQF_TRIGGER_RISING, "TE_GPIO", par);
> if (rc)
> return dev_err_probe(dev, rc, "TE IRQ request
> failed.\n"); disable_irq_nosync(irq);
> return irq;
> }
>
hi, i have modified it according to your suggestion like below:
static irqreturn_t panel_te_handler(int irq, void *data)
{
struct fbtft_par *par = (struct fbtft_par *)data;
complete(&par->panel_te);
return IRQ_HANDLED;
}
/**
* init_tearing_effect_line() - init tearing effect line
*
* @par: FBTFT parameter object
*
* Return: 0 on success, < 0 if error occurred.
*/
static int init_tearing_effect_line(struct fbtft_par *par)
{
struct device *dev = par->info->device;
struct gpio_desc *te;
int rc;
te = gpiod_get_optional(dev, "te", GPIOD_IN);
if (IS_ERR(te))
return dev_err_probe(dev, PTR_ERR(te), "Failed to
request te GPIO\n");
if (te) {
par->irq_te = gpiod_to_irq(te);
gpiod_put(te);
if (par->irq_te) {
rc = devm_request_irq(dev,
par->irq_te,
panel_te_handler,
IRQF_TRIGGER_RISING,
"TE_GPIO", par);
if (rc)
return dev_err_probe(dev, rc, "TE IRQ
request failed.\n");
disable_irq_nosync(par->irq_te);
init_completion(&par->panel_te);
} else {
return dev_err_probe(dev, par->irq_te, "gpiod
to TE IRQ failed.\n");
}
}
return 0;
}
/**
* init_display() - initialize the display controller
*
* @par: FBTFT parameter object
*
* Most of the commands in this init function set their parameters to
the
* same default values which are already in place after the display has
been
* powered up. (The main exception to this rule is the pixel format
which
* would default to 18 instead of 16 bit per pixel.)
* Nonetheless, this sequence can be used as a template for concrete
* displays which usually need some adjustments.
*
* Return: 0 on success, < 0 if error occurred.
*/
static int init_display(struct fbtft_par *par)
{
int rc;
rc = init_tearing_effect_line(par);
if (rc < 0)
return rc;
......
if (par->irq_te)
write_reg(par, MIPI_DCS_SET_TEAR_ON, 0x00);
......
/**
* st7789v_write_vmem16_bus8() - write data to display
*
* @par: FBTFT parameter object
* @offset: offset from screen_buffer
* @len: the length of data to be written
*
* 16 bit pixel over 8-bit databus
*
* Return: 0 on success, or a negative error code otherwise.
*/
static int st7789v_write_vmem16_bus8(struct fbtft_par *par, size_t
offset, size_t len)
{
struct device *dev = par->info->device;
__be16 *txbuf16 = par->txbuf.buf;
size_t startbyte_size = 0;
size_t tx_array_size;
size_t to_copy;
size_t remain;
u16 *vmem16;
int ret = 0;
int i;
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);
gpiod_set_value(par->gpio.dc, 1);
if (par->irq_te) {
enable_irq(par->irq_te);
reinit_completion(&par->panel_te);
ret = wait_for_completion_timeout(&par->panel_te,
msecs_to_jiffies(PANEL_TE_TIMEOUT_MS));
if (ret == 0)
dev_err(dev, "wait panel TE time out\n");
disable_irq(par->irq_te);
}
> Note, when you define proper fields for IRQ line and completion in the
> data structure the above can be amended accordingly.
>
> ...
>
> > + /* tearing effect line on */
> > + if (par->gpio.te)
> > + write_reg(par, 0x35, 0x00);
>
> 0x35 is defined. use it and drop useless comments.
>
> ...
>
> > /**
> > + * st7789v_write_vmem16_bus8() - write data to display
>
> > + *
>
> Redundant blank line.
>
> > + * @par: FBTFT parameter object
> > + * @offset: offset from screen_buffer
> > + * @len: the length of data to be written
> > + *
> > + * 16 bit pixel over 8-bit databus
> > + *
> > + * Return: 0 on success, < 0 if error occurred.
>
> ", or a negative error code otherwise"
>
> > + */
>
> > +
> Redundant blank line
>
> > +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;
>
> Reversed xmas tree order.
>
> > + 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)
>
> Useless duplicate check.
>
> > + gpiod_set_value(par->gpio.dc, 1);
>
> > + if (par->gpio.te) {
> > + enable_irq(gpiod_to_irq(par->gpio.te));
>
> Here you should use the IRQ line rather than the GPIO descriptor. See
> above.
>
> > + reinit_completion(&spi_panel_te);
> > + ret = wait_for_completion_timeout(&spi_panel_te,
> > +
> > msecs_to_jiffies(SPI_PANEL_TE_TIMEOUT));
> > + if (ret == 0)
> > + dev_err(par->info->device, "wait panel TE
> > time out\n"); +
> > + disable_irq(gpiod_to_irq(par->gpio.te));
> > + }
>
> > +
> > + while (remain) {
> > + to_copy = min(tx_array_size, remain);
>
> > + dev_dbg(par->info->device, " to_copy=%zu,
> > remain=%zu\n",
> > + to_copy, remain - to_copy);
>
> Like in previous functions create a temporary variable to keep a
> pointer to struct device and use it here and everywhere else. It might
> save you LOCs and make code easier to read and understand.
>
> > + for (i = 0; i < to_copy; i++)
> > + txbuf16[i] = cpu_to_be16(vmem16[i]);
>
> If both of them are 16-bit wide, consider moving this to a helper
> which somebody can move to byteorder/generic.h in the future.
>
> > + vmem16 = vmem16 + to_copy;
> > + ret = par->fbtftops.write(par, par->txbuf.buf,
> > + startbyte_size + to_copy *
> > 2);
> > + if (ret < 0)
> > + return ret;
> > + remain -= to_copy;
> > + }
> > +
> > + return ret;
> > +}
>
regards,
Carlis
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