Stabilizing PLL needs to be waited for. This is done using a loop, checking the PLL_STABLE bit in the status register.
DSIM fires an interrupt when the PLL is stabilized. Rely on this functionality for stabilization wait, getting rid of the implicit loop. This has been tested on a Galaxy J6 (Exynos 7870). Unfortunately, since testing on all supported devices is less feasible, introduce a stop-gap measure where the timeout has a gracious lower bound of 100 microseconds. This will (hopefully) prevent regressions due to timeout on other devices. Suggested-by: Inki Dae <[email protected]> Link: https://lore.kernel.org/r/caaqkjzmlmbwdvzrb5+xb_5yz3aep4uuzfjmuuzy9nfdu13v...@mail.gmail.com Signed-off-by: Kaustabh Chakraborty <[email protected]> --- drivers/gpu/drm/bridge/samsung-dsim.c | 41 +++++++++++++++++++++++------------ include/drm/bridge/samsung-dsim.h | 1 + 2 files changed, 28 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c index 91f230953a49f..14d78e41886ee 100644 --- a/drivers/gpu/drm/bridge/samsung-dsim.c +++ b/drivers/gpu/drm/bridge/samsung-dsim.c @@ -17,6 +17,7 @@ #include <linux/export.h> #include <linux/irq.h> #include <linux/media-bus-format.h> +#include <linux/minmax.h> #include <linux/of.h> #include <linux/phy/phy.h> #include <linux/platform_device.h> @@ -788,7 +789,7 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi, { const struct samsung_dsim_driver_data *driver_data = dsi->driver_data; unsigned long fin, fout; - int timeout; + unsigned int timeout; u8 p, s; u16 m; u32 reg; @@ -849,19 +850,26 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi, if (dsi->swap_dn_dp_data) reg |= DSIM_PLL_DPDNSWAP_DAT; + /* + * The PLL_TIMER value is the product of the timeout delay and the APB + * bus clock rate. Calcutate the timeout delay on-the-fly here. + * It is assumed that the bus clock is the first clock in the provided + * bulk clock data. + */ + timeout = 100; + fin = clk_get_rate(dsi->driver_data->clk_data[0].clk) / HZ_PER_MHZ; + if (fin) + timeout = max(dsi->driver_data->reg_values[PLL_TIMER] / fin, + timeout); + + reinit_completion(&dsi->pll_stabilized); samsung_dsim_write(dsi, DSIM_PLLCTRL_REG, reg); - timeout = 3000; - do { - if (timeout-- == 0) { - dev_err(dsi->dev, "PLL failed to stabilize\n"); - return 0; - } - if (driver_data->has_legacy_status_reg) - reg = samsung_dsim_read(dsi, DSIM_STATUS_REG); - else - reg = samsung_dsim_read(dsi, DSIM_LINK_STATUS_REG); - } while ((reg & BIT(driver_data->pll_stable_bit)) == 0); + if (wait_for_completion_timeout(&dsi->pll_stabilized, + usecs_to_jiffies(timeout))) { + dev_err(dsi->dev, "PLL failed to stabilize\n"); + return 0; + } dsi->hs_clock = fout; @@ -1596,8 +1604,12 @@ static irqreturn_t samsung_dsim_irq(int irq, void *dev_id) return IRQ_HANDLED; } - if (!(status & (DSIM_INT_RX_DONE | DSIM_INT_SFR_FIFO_EMPTY | - DSIM_INT_PLL_STABLE))) + if (status & DSIM_INT_PLL_STABLE) { + complete(&dsi->pll_stabilized); + return IRQ_HANDLED; + } + + if (!(status & (DSIM_INT_RX_DONE | DSIM_INT_SFR_FIFO_EMPTY))) return IRQ_HANDLED; if (samsung_dsim_transfer_finish(dsi)) @@ -2147,6 +2159,7 @@ int samsung_dsim_probe(struct platform_device *pdev) return PTR_ERR(dsi); init_completion(&dsi->completed); + init_completion(&dsi->pll_stabilized); spin_lock_init(&dsi->transfer_lock); INIT_LIST_HEAD(&dsi->transfer_list); diff --git a/include/drm/bridge/samsung-dsim.h b/include/drm/bridge/samsung-dsim.h index 03005e474704b..e3433da21ad08 100644 --- a/include/drm/bridge/samsung-dsim.h +++ b/include/drm/bridge/samsung-dsim.h @@ -123,6 +123,7 @@ struct samsung_dsim { int state; struct drm_property *brightness; struct completion completed; + struct completion pll_stabilized; spinlock_t transfer_lock; /* protects transfer_list */ struct list_head transfer_list; -- 2.52.0
