diff options
Diffstat (limited to 'drivers/clk/rockchip/clk-mmc-phase.c')
| -rw-r--r-- | drivers/clk/rockchip/clk-mmc-phase.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/drivers/clk/rockchip/clk-mmc-phase.c b/drivers/clk/rockchip/clk-mmc-phase.c index 077fcdc7908b..fe7d9ed1d436 100644 --- a/drivers/clk/rockchip/clk-mmc-phase.c +++ b/drivers/clk/rockchip/clk-mmc-phase.c @@ -58,6 +58,12 @@ static int rockchip_mmc_get_phase(struct clk_hw *hw) u16 degrees; u32 delay_num = 0; + /* See the comment for rockchip_mmc_set_phase below */ + if (!rate) { + pr_err("%s: invalid clk rate\n", __func__); + return -EINVAL; + } + raw_value = readl(mmc_clock->reg) >> (mmc_clock->shift); degrees = (raw_value & ROCKCHIP_MMC_DEGREE_MASK) * 90; @@ -84,6 +90,23 @@ static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees) u32 raw_value; u32 delay; + /* + * The below calculation is based on the output clock from + * MMC host to the card, which expects the phase clock inherits + * the clock rate from its parent, namely the output clock + * provider of MMC host. However, things may go wrong if + * (1) It is orphan. + * (2) It is assigned to the wrong parent. + * + * This check help debug the case (1), which seems to be the + * most likely problem we often face and which makes it difficult + * for people to debug unstable mmc tuning results. + */ + if (!rate) { + pr_err("%s: invalid clk rate\n", __func__); + return -EINVAL; + } + nineties = degrees / 90; remainder = (degrees % 90); |