[PATCH v12] staging: fbtft: add tearing signal detect
Andy Shevchenko
andy.shevchenko at gmail.com
Thu Jan 28 14:33:02 UTC 2021
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.
> 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;
}
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;
> +}
--
With Best Regards,
Andy Shevchenko
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