Allow the dclk to reset its rate when a rate change is initiated from an ancestor clock. This makes it possible to no longer to get an exclusive lock. As a consequence, it is now possible to set new rates if necessary, e.g. when an external display is connected. The first user of this functionality is the A64 because PLL-VIDEO0 is an ancestor for both HDMI and TCON0. This allows to select an optimal rate for TCON0 as long as there is no external HDMI connection. Once a change in PLL-VIDEO0 is performed when an HDMI connection is established, TCON0 can react gracefully and select an optimal rate based on this the new constraint. Signed-off-by: Frank Oltmanns <frank@xxxxxxxxxxxx> --- I would like to make the Allwinner A64's data-clock keep its rate when its ancestor's (pll-video0) rate changes. Keeping data-clock's rate is required, to let the A64 drive both an LCD and HDMI display at the same time, because both have pll-video0 as an ancestor. TCONs that use this flag store the ideal rate for their data-clock and subscribe to be notified when data-clock changes. When rate setting has finished (indicated by a POST_RATE_CHANGE event) the call back function schedules delayed work to set the data-clock's rate to the initial value after 100 ms. Using delayed work maks sure that the clock setting is finished. I've implemented this functionality as a quirk, so that it is possible to use it only for the A64. This patch supersedes [1]. This work is inspired by an out-of-tree patchset [2] [3] [4]. Unfortunately, the patchset uses clk_set_rate() directly in a notifier callback, which the following comment on clk_notifier_register() forbids: "The callbacks associated with the notifier must not re-enter into the clk framework by calling any top-level clk APIs." [5] Furthermore, that out-of-tree patchset no longer works since 6.6, because setting pll-mipi is now also resetting pll-video0 and therefore causes a race condition. Thank you for considering this contribution, Frank [1] https://lore.kernel.org/lkml/20230825-pll-mipi_keep_rate-v1-0-35bc43570730@xxxxxxxxxxxx/ [2] https://codeberg.org/megi/linux/commit/a37cda2fff41a67a2bacf82b1594e10335d0bd8a [3] https://codeberg.org/megi/linux/commit/24dc09128d2c8efc6ddf19249420e9798e967a46 [4] https://codeberg.org/megi/linux/commit/728a93d46f99f0eb231ed6fa8971a45f97c7182c [5] https://elixir.bootlin.com/linux/v6.7.9/source/drivers/clk/clk.c#L4669 --- drivers/gpu/drm/sun4i/sun4i_tcon.c | 70 ++++++++++++++++++++++++++++++++++---- drivers/gpu/drm/sun4i/sun4i_tcon.h | 12 +++++++ 2 files changed, 76 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c index a1a2c845ade0..b880bd44049a 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c @@ -108,9 +108,11 @@ static void sun4i_tcon_channel_set_status(struct sun4i_tcon *tcon, int channel, if (enabled) { clk_prepare_enable(clk); - clk_rate_exclusive_get(clk); + if (!tcon->quirks->restores_rate) + clk_rate_exclusive_get(clk); } else { - clk_rate_exclusive_put(clk); + if (!tcon->quirks->restores_rate) + clk_rate_exclusive_put(clk); clk_disable_unprepare(clk); } } @@ -343,6 +345,53 @@ static void sun4i_tcon0_mode_set_dithering(struct sun4i_tcon *tcon, regmap_write(tcon->regs, SUN4I_TCON_FRM_CTL_REG, val); } +static void sun4i_rate_reset_notifier_delayed_update(struct work_struct *work) +{ + struct sun4i_rate_reset_nb *rate_reset = container_of(work, struct sun4i_rate_reset_nb, + reset_rate_work.work); + + clk_set_rate(rate_reset->target_clk, rate_reset->saved_rate); +} + +static int sun4i_rate_reset_notifier_cb(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct sun4i_rate_reset_nb *rate_reset = to_sun4i_rate_reset_nb(nb); + + if (event == POST_RATE_CHANGE) + schedule_delayed_work(&rate_reset->reset_rate_work, msecs_to_jiffies(100)); + + return NOTIFY_DONE; +} + +static void sun4i_rate_reset_notifier_register(struct sun4i_rate_reset_nb *rate_reset_nb) +{ + if (rate_reset_nb->is_registered) + return; + + rate_reset_nb->clk_nb.notifier_call = sun4i_rate_reset_notifier_cb; + + INIT_DELAYED_WORK(&rate_reset_nb->reset_rate_work, + sun4i_rate_reset_notifier_delayed_update); + + if (!clk_notifier_register(rate_reset_nb->target_clk, + &rate_reset_nb->clk_nb)) + rate_reset_nb->is_registered = true; +} + +static struct sun4i_rate_reset_nb tcon_rate_reset_tcon0_nb; + +static void sun4i_tcon0_set_dclk_rate(struct sun4i_tcon *tcon, unsigned long rate) +{ + clk_set_rate(tcon->dclk, rate); + + if (tcon->quirks->restores_rate) { + tcon_rate_reset_tcon0_nb.target_clk = tcon->dclk; + tcon_rate_reset_tcon0_nb.saved_rate = rate; + sun4i_rate_reset_notifier_register(&tcon_rate_reset_tcon0_nb); + } +} + static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon, const struct drm_encoder *encoder, const struct drm_display_mode *mode) @@ -360,8 +409,8 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon, */ tcon->dclk_min_div = SUN6I_DSI_TCON_DIV; tcon->dclk_max_div = SUN6I_DSI_TCON_DIV; - clk_set_rate(tcon->dclk, mode->crtc_clock * 1000 * (bpp / lanes) - / SUN6I_DSI_TCON_DIV); + sun4i_tcon0_set_dclk_rate(tcon, mode->crtc_clock * 1000 * (bpp / lanes) + / SUN6I_DSI_TCON_DIV); /* Set the resolution */ regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG, @@ -434,7 +483,7 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon, tcon->dclk_min_div = 7; tcon->dclk_max_div = 7; - clk_set_rate(tcon->dclk, mode->crtc_clock * 1000); + sun4i_tcon0_set_dclk_rate(tcon, mode->crtc_clock * 1000); /* Set the resolution */ regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG, @@ -516,7 +565,7 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon, tcon->dclk_min_div = tcon->quirks->dclk_min_div; tcon->dclk_max_div = 127; - clk_set_rate(tcon->dclk, mode->crtc_clock * 1000); + sun4i_tcon0_set_dclk_rate(tcon, mode->crtc_clock * 1000); /* Set the resolution */ regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG, @@ -1503,6 +1552,14 @@ static const struct sun4i_tcon_quirks sun8i_a33_quirks = { .supports_lvds = true, }; +static const struct sun4i_tcon_quirks sun50i_a64_lcd_quirks = { + .supports_lvds = true, + .has_channel_0 = true, + .restores_rate = true, + .dclk_min_div = 1, + .setup_lvds_phy = sun6i_tcon_setup_lvds_phy, +}; + static const struct sun4i_tcon_quirks sun8i_a83t_lcd_quirks = { .supports_lvds = true, .has_channel_0 = true, @@ -1561,6 +1618,7 @@ const struct of_device_id sun4i_tcon_of_table[] = { { .compatible = "allwinner,sun9i-a80-tcon-tv", .data = &sun9i_a80_tcon_tv_quirks }, { .compatible = "allwinner,sun20i-d1-tcon-lcd", .data = &sun20i_d1_lcd_quirks }, { .compatible = "allwinner,sun20i-d1-tcon-tv", .data = &sun8i_r40_tv_quirks }, + { .compatible = "allwinner,sun50i-a64-tcon-lcd", .data = &sun50i_a64_lcd_quirks }, { } }; MODULE_DEVICE_TABLE(of, sun4i_tcon_of_table); diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h index fa23aa23fe4a..bd4abc90062b 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.h +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h @@ -243,6 +243,7 @@ struct sun4i_tcon_quirks { bool needs_edp_reset; /* a80 edp reset needed for tcon0 access */ bool supports_lvds; /* Does the TCON support an LVDS output? */ bool polarity_in_ch0; /* some tcon1 channels have polarity bits in tcon0 pol register */ + bool restores_rate; /* restores the initial rate when rate changes */ u8 dclk_min_div; /* minimum divider for TCON0 DCLK */ /* callback to handle tcon muxing options */ @@ -300,4 +301,15 @@ void sun4i_tcon_set_status(struct sun4i_tcon *crtc, extern const struct of_device_id sun4i_tcon_of_table[]; +struct sun4i_rate_reset_nb { + struct notifier_block clk_nb; + struct delayed_work reset_rate_work; + + struct clk *target_clk; + unsigned long saved_rate; + bool is_registered; +}; + +#define to_sun4i_rate_reset_nb(_nb) container_of(_nb, struct sun4i_rate_reset_nb, clk_nb) + #endif /* __SUN4I_TCON_H__ */ --- base-commit: dcb6c8ee6acc6c347caec1e73fb900c0f4ff9806 change-id: 20240304-tcon_keep_stable_rate-5729c7706343 Best regards, -- Frank Oltmanns <frank@xxxxxxxxxxxx>
