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Message-ID: <20251231145712.60816-1-marek.vasut+renesas@mailbox.org>
Date: Wed, 31 Dec 2025 15:56:10 +0100
From: Marek Vasut <marek.vasut+renesas@...lbox.org>
To: dri-devel@...ts.freedesktop.org
Cc: Marek Vasut <marek.vasut+renesas@...lbox.org>,
kernel test robot <lkp@...el.com>,
David Airlie <airlied@...il.com>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Magnus Damm <magnus.damm@...il.com>,
Maxime Ripard <mripard@...nel.org>,
Simona Vetter <simona@...ll.ch>,
Thomas Zimmermann <tzimmermann@...e.de>,
Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>,
linux-kernel@...r.kernel.org,
linux-renesas-soc@...r.kernel.org
Subject: [PATCH] drm/rcar-du: dsi: Clean up VCLK divider calculation
Currently, in rcar_mipi_dsi_parameters_calc(), the VCLK divider is stored
in setup_info structure as BIT(divider). The rcar_mipi_dsi_parameters_calc()
is called at the early beginning of rcar_mipi_dsi_startup() function. Later,
in the same rcar_mipi_dsi_startup() function, the stored BIT(divider) value
is passed to __ffs() to calculate back the divider out of the value again.
Factor out VCLK divider calculation into rcar_mipi_dsi_vclk_divider()
function and call the function from both rcar_mipi_dsi_parameters_calc()
and rcar_mipi_dsi_startup() to avoid this back and forth BIT() and _ffs()
and avoid unnecessarily storing the divider value in setup_info at all.
This rework has a slight side-effect, in that it should allow the compiler
to better evaluate the code and avoid compiler warnings about variable
value overflows, which can never happen.
Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202512051834.bESvhDiG-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202512222321.TeY4VbvK-lkp@intel.com/
Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>
---
Cc: David Airlie <airlied@...il.com>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>
Cc: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Cc: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Magnus Damm <magnus.damm@...il.com>
Cc: Maxime Ripard <mripard@...nel.org>
Cc: Simona Vetter <simona@...ll.ch>
Cc: Thomas Zimmermann <tzimmermann@...e.de>
Cc: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
Cc: dri-devel@...ts.freedesktop.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-renesas-soc@...r.kernel.org
---
.../gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c | 35 ++++++++++++++-----
1 file changed, 26 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c b/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
index 4ef2e3c129ed7..875945bf8255b 100644
--- a/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
+++ b/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
@@ -84,7 +84,6 @@ struct dsi_setup_info {
unsigned long fout;
u16 m;
u16 n;
- u16 vclk_divider;
const struct dsi_clk_config *clkset;
};
@@ -335,10 +334,24 @@ rcar_mipi_dsi_post_init_phtw_v4h(struct rcar_mipi_dsi *dsi,
* Hardware Setup
*/
+static unsigned int rcar_mipi_dsi_vclk_divider(struct rcar_mipi_dsi *dsi,
+ struct dsi_setup_info *setup_info)
+{
+ switch (dsi->info->model) {
+ case RCAR_DSI_V3U:
+ default:
+ return (setup_info->clkset->vco_cntrl >> 4) & 0x3;
+
+ case RCAR_DSI_V4H:
+ return (setup_info->clkset->vco_cntrl >> 3) & 0x7;
+ }
+}
+
static void rcar_mipi_dsi_pll_calc(struct rcar_mipi_dsi *dsi,
unsigned long fin_rate,
unsigned long fout_target,
- struct dsi_setup_info *setup_info)
+ struct dsi_setup_info *setup_info,
+ u16 vclk_divider)
{
unsigned int best_err = -1;
const struct rcar_mipi_dsi_device_info *info = dsi->info;
@@ -360,7 +373,7 @@ static void rcar_mipi_dsi_pll_calc(struct rcar_mipi_dsi *dsi,
if (fout < info->fout_min || fout > info->fout_max)
continue;
- fout = div64_u64(fout, setup_info->vclk_divider);
+ fout = div64_u64(fout, vclk_divider);
if (fout < setup_info->clkset->min_freq ||
fout > setup_info->clkset->max_freq)
@@ -390,7 +403,9 @@ static void rcar_mipi_dsi_parameters_calc(struct rcar_mipi_dsi *dsi,
unsigned long fout_target;
unsigned long fin_rate;
unsigned int i;
+ unsigned int div;
unsigned int err;
+ u16 vclk_divider;
/*
* Calculate Fout = dot clock * ColorDepth / (2 * Lane Count)
@@ -412,18 +427,20 @@ static void rcar_mipi_dsi_parameters_calc(struct rcar_mipi_dsi *dsi,
fin_rate = clk_get_rate(clk);
+ div = rcar_mipi_dsi_vclk_divider(dsi, setup_info);
+
switch (dsi->info->model) {
case RCAR_DSI_V3U:
default:
- setup_info->vclk_divider = 1 << ((clk_cfg->vco_cntrl >> 4) & 0x3);
+ vclk_divider = BIT_U32(div);
break;
case RCAR_DSI_V4H:
- setup_info->vclk_divider = 1 << (((clk_cfg->vco_cntrl >> 3) & 0x7) + 1);
+ vclk_divider = BIT_U32(div + 1);
break;
}
- rcar_mipi_dsi_pll_calc(dsi, fin_rate, fout_target, setup_info);
+ rcar_mipi_dsi_pll_calc(dsi, fin_rate, fout_target, setup_info, vclk_divider);
/* Find hsfreqrange */
setup_info->hsfreq = setup_info->fout * 2;
@@ -439,7 +456,7 @@ static void rcar_mipi_dsi_parameters_calc(struct rcar_mipi_dsi *dsi,
dev_dbg(dsi->dev,
"Fout = %u * %lu / (%u * %u * %u) = %lu (target %lu Hz, error %d.%02u%%)\n",
setup_info->m, fin_rate, dsi->info->n_mul, setup_info->n,
- setup_info->vclk_divider, setup_info->fout, fout_target,
+ vclk_divider, setup_info->fout, fout_target,
err / 100, err % 100);
dev_dbg(dsi->dev,
@@ -653,11 +670,11 @@ static int rcar_mipi_dsi_startup(struct rcar_mipi_dsi *dsi,
switch (dsi->info->model) {
case RCAR_DSI_V3U:
default:
- vclkset |= VCLKSET_DIV_V3U(__ffs(setup_info.vclk_divider));
+ vclkset |= VCLKSET_DIV_V3U(rcar_mipi_dsi_vclk_divider(dsi, &setup_info));
break;
case RCAR_DSI_V4H:
- vclkset |= VCLKSET_DIV_V4H(__ffs(setup_info.vclk_divider) - 1);
+ vclkset |= VCLKSET_DIV_V4H(rcar_mipi_dsi_vclk_divider(dsi, &setup_info));
break;
}
--
2.51.0
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