linux-kernel - [PATCH 6/6] drm/stm: add an option to change FB bpp

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Date:   Thu,  1 Jun 2023 19:03:20 +0200
From:   Dario Binacchi <dario.binacchi@...rulasolutions.com>
To:     linux-kernel@...r.kernel.org
Cc:     Amarula patchwork <linux-amarula@...rulasolutions.com>,
        michael@...rulasolutions.com,
        Dario Binacchi <dario.binacchi@...rulasolutions.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Philippe Cornu <philippe.cornu@...s.st.com>,
        Raphael Gallais-Pou <raphael.gallais-pou@...s.st.com>,
        Yannick Fertre <yannick.fertre@...s.st.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com
Subject: [PATCH 6/6] drm/stm: add an option to change FB bpp

Boards that use the STM32F{4,7} series have limited amounts of RAM. The
added parameter allows users to size, within certain limits, the memory
footprint required by the framebuffer.

Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>

---

 drivers/gpu/drm/stm/drv.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/stm/drv.c b/drivers/gpu/drm/stm/drv.c
index 422220df7d8c..65be2b442a6a 100644
--- a/drivers/gpu/drm/stm/drv.c
+++ b/drivers/gpu/drm/stm/drv.c
@@ -30,6 +30,11 @@
 #define STM_MAX_FB_WIDTH	2048
 #define STM_MAX_FB_HEIGHT	2048 /* same as width to handle orientation */
 
+static uint stm_bpp = 16;
+
+MODULE_PARM_DESC(bpp, "bits-per-pixel (default: 16)");
+module_param_named(bpp, stm_bpp, uint, 0644);
+
 static const struct drm_mode_config_funcs drv_mode_config_funcs = {
 	.fb_create = drm_gem_fb_create,
 	.atomic_check = drm_atomic_helper_check,
@@ -93,6 +98,7 @@ static int drv_load(struct drm_device *ddev)
 	ddev->mode_config.min_height = 0;
 	ddev->mode_config.max_width = STM_MAX_FB_WIDTH;
 	ddev->mode_config.max_height = STM_MAX_FB_HEIGHT;
+	ddev->mode_config.preferred_depth = stm_bpp;
 	ddev->mode_config.funcs = &drv_mode_config_funcs;
 	ddev->mode_config.normalize_zpos = true;
 
@@ -203,7 +209,7 @@ static int stm_drm_platform_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_put;
 
-	drm_fbdev_dma_setup(ddev, 16);
+	drm_fbdev_dma_setup(ddev, stm_bpp);
 
 	return 0;
 
-- 
2.32.0