Messages in this thread Patch in this message | | | Subject | Re: [BUG] SPI broken for SPI based panel drivers | From | "H. Nikolaus Schaller" <> | Date | Tue, 1 Dec 2020 17:46:56 +0100 |
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> Am 01.12.2020 um 16:52 schrieb Sven Van Asbroeck <thesven73@gmail.com>: > > Nikolaus, > > On Tue, Dec 1, 2020 at 9:38 AM H. Nikolaus Schaller <hns@goldelico.com> wrote: >> >> Let's work on a fix for the fix now. > > I tested spi-gpio on my system, by converting a built-in or hardware spi, > to a spi-gpio. Interestingly, the patch has the opposite effect on my system: > before the patch, spi-gpio did not work, but after it's applied, it does work. > > Can you tell me the idle status of your chip-select gpio in debugfs? > # mount -t debugfs none /sys/kernel/debug > # cat /sys/kernel/debug/gpio > Look for something like this: > gpiochip0: GPIOs 0-31, parent: platform/209c000.gpio, 209c000.gpio: > gpio-17 ( |spi5 CS0 ) out hi ACTIVE LOW
root@letux:~# mount -t debugfs none /sys/kernel/debug root@letux:~# cat /sys/kernel/debug/gpio|fgrep spi gpio-179 ( |spi4 CS0 ) out lo root@letux:~#
That is after the panel driver did send the commands.
> > Also, apply the following patch, and tell me > a) does this dev_err() get called on your system, and
yes. Many times.
> b) what is the value when your chip is de-selected
root@letux:~# dmesg|fgrep td028 [ 14.530456] panel-tpo-td028ttec1 spi4.0: spi->mode = 00000003 [ 14.599212] panel-tpo-td028ttec1 spi4.0: gpiod disable [ 14.817871] panel-tpo-td028ttec1 spi4.0: spi->mode = 00000003 [ 14.817871] panel-tpo-td028ttec1 spi4.0: gpiod enable
So it is disabled first and then enabled. Which appears to be the opposite of what it should be.
BTW: I have added another dev_err to print the spi->mode and like you describe it is (overwritten? by SPI_MODE_3.
I can check what value it has in the driver before it is set to SPI_MODE_3.
Maybe, there the spi-cs-high gets lost?
BR and thanks, Nikolaus
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index 7e8804b02be9..b2f4cf5c9ffb 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -813,11 +813,12 @@ static void spi_set_cs(struct spi_device *spi, > bool enable) > > if (spi->cs_gpiod || gpio_is_valid(spi->cs_gpio)) { > if (!(spi->mode & SPI_NO_CS)) { > - if (spi->cs_gpiod) > + if (spi->cs_gpiod) { > + dev_err(&spi->dev, "gpiod %s", enable1 > ? "enable" : "disable"); > /* polarity handled by gpiolib */ > gpiod_set_value_cansleep(spi->cs_gpiod, > enable1); > - else > + } else > /* > * invert the enable line, as active low is > * default for SPI.
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