| Message ID | 20231116180743.2763021-3-javierm@redhat.com (mailing list archive) |
|---|---|
| State | Rejected |
| Headers | show |
| Series | [1/3] dt-bindings: display: ssd1307fb: Change "solomon, page-offset" default value | expand |
On Thu, Nov 16, 2023 at 07:07:39PM +0100, Javier Martinez Canillas wrote: > This is used to specify the page start address offset of the display RAM. > > The value is used as offset when setting the page start address with the > SSD130X_SET_PAGE_RANGE command, and the driver currently sets its value to > 1 if the property is not present in the Device Tree. > > But the datasheet mentions that the value on reset for the page start is a > 0, so it makes more sense to also have 0 as the default value for the page > offset if the property is not present. I can see the argument, but that's a DT ABI breaking change. > In fact, using a default value of 1 leads to the display not working when > the emulated fbdev is attached to the framebuffer console. Could we fix that one instead? What is the issue about, exactly Maxime
Maxime Ripard <mripard@kernel.org> writes: Hello Maxime, > On Thu, Nov 16, 2023 at 07:07:39PM +0100, Javier Martinez Canillas wrote: >> This is used to specify the page start address offset of the display RAM. >> >> The value is used as offset when setting the page start address with the >> SSD130X_SET_PAGE_RANGE command, and the driver currently sets its value to >> 1 if the property is not present in the Device Tree. >> >> But the datasheet mentions that the value on reset for the page start is a >> 0, so it makes more sense to also have 0 as the default value for the page >> offset if the property is not present. > > I can see the argument, but that's a DT ABI breaking change. > Yes, I know it's a DT ABI breaking change but what I'm trying to argue is that the DT binding schema isn't correct to start with. Even the RPi DTBO for this device (which I guess is used by most people with a SSD1306) has a property to explicitly set this to 0: ssd1306: oled@3c{ ... solomon,page-offset = <0>; ... }; https://github.com/raspberrypi/linux/blob/rpi-6.1.y/arch/arm/boot/dts/overlays/ssd1306-overlay.dts >> In fact, using a default value of 1 leads to the display not working when >> the emulated fbdev is attached to the framebuffer console. > > Could we fix that one instead? What is the issue about, exactly > This is the issue that Sahaj reported: https://twitter.com/sahajsarup/status/1725088484736766364 I can try to figure out how to make the fbcon to work with a page-offset=1 but didn't investigate since thought that 0 is a much better default. Just like the maximum resolution is the default if no width and height are set. > Maxime
diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c index bef293922b98..8944129a8e0b 100644 --- a/drivers/gpu/drm/solomon/ssd130x.c +++ b/drivers/gpu/drm/solomon/ssd130x.c @@ -1453,7 +1453,7 @@ static void ssd130x_parse_properties(struct ssd130x_device *ssd130x) ssd130x->height = ssd130x->device_info->default_height; if (device_property_read_u32(dev, "solomon,page-offset", &ssd130x->page_offset)) - ssd130x->page_offset = 1; + ssd130x->page_offset = 0; if (device_property_read_u32(dev, "solomon,col-offset", &ssd130x->col_offset)) ssd130x->col_offset = 0;
This is used to specify the page start address offset of the display RAM. The value is used as offset when setting the page start address with the SSD130X_SET_PAGE_RANGE command, and the driver currently sets its value to 1 if the property is not present in the Device Tree. But the datasheet mentions that the value on reset for the page start is a 0, so it makes more sense to also have 0 as the default value for the page offset if the property is not present. In fact, using a default value of 1 leads to the display not working when the emulated fbdev is attached to the framebuffer console. Reported-by: Sahaj Sarup <sahaj.sarup@linaro.org> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> --- drivers/gpu/drm/solomon/ssd130x.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)