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memory: tegra30-emc: Firm up suspend/resume sequence 

The current code doesn't prevent race conditions of suspend/resume vs CCF.
Let's take exclusive control over the EMC clock during suspend in a way
that is free from race conditions.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
This commit is contained in:
Dmitry Osipenko 2019-12-20 05:08:47 +03:00 committed by Thierry Reding
parent 5f5636ef1d
commit 51bb73f934
1 changed files with 20 additions and 18 deletions
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38
drivers/memory/tegra/tegra30-emc.c
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@ -346,7 +346,6 @@ struct tegra_emc {
bool vref_cal_toggle : 1;
bool zcal_long : 1;
bool dll_on : 1;
bool prepared : 1;
bool bad_state : 1;
struct {
@ -758,9 +757,6 @@ static int emc_prepare_timing_change(struct tegra_emc *emc, unsigned long rate)
/* interrupt can be re-enabled now */
enable_irq(emc->irq);
emc->bad_state = false;
emc->prepared = true;
return 0;
}
@ -769,13 +765,12 @@ static int emc_complete_timing_change(struct tegra_emc *emc,
{
struct emc_timing *timing = emc_find_timing(emc, rate);
unsigned long timeout;
int ret;
int err;
timeout = wait_for_completion_timeout(&emc->clk_handshake_complete,
msecs_to_jiffies(100));
if (timeout == 0) {
dev_err(emc->dev, "emc-car handshake failed\n");
emc->bad_state = true;
return -EIO;
}
@ -797,22 +792,23 @@ static int emc_complete_timing_change(struct tegra_emc *emc,
udelay(2);
/* update restored timing */
ret = emc_seq_update_timing(emc);
if (ret)
emc->bad_state = true;
err = emc_seq_update_timing(emc);
/* restore early ACK */
mc_writel(emc->mc, emc->mc_override, MC_EMEM_ARB_OVERRIDE);
emc->prepared = false;
if (err)
return err;
return ret;
emc->bad_state = false;
return 0;
}
static int emc_unprepare_timing_change(struct tegra_emc *emc,
unsigned long rate)
{
if (emc->prepared && !emc->bad_state) {
if (!emc->bad_state) {
/* shouldn't ever happen in practice */
dev_err(emc->dev, "timing configuration can't be reverted\n");
emc->bad_state = true;
@ -1354,13 +1350,17 @@ unset_cb:
static int tegra_emc_suspend(struct device *dev)
{
struct tegra_emc *emc = dev_get_drvdata(dev);
int err;
/*
* Suspending in a bad state will hang machine. The "prepared" var
* shall be always false here unless it's a kernel bug that caused
* suspending in a wrong order.
*/
if (WARN_ON(emc->prepared) || emc->bad_state)
/* take exclusive control over the clock's rate */
err = clk_rate_exclusive_get(emc->clk);
if (err) {
dev_err(emc->dev, "failed to acquire clk: %d\n", err);
return err;
}
/* suspending in a bad state will hang machine */
if (WARN(emc->bad_state, "hardware in a bad state\n"))
return -EINVAL;
emc->bad_state = true;
@ -1375,6 +1375,8 @@ static int tegra_emc_resume(struct device *dev)
emc_setup_hw(emc);
emc->bad_state = false;
clk_rate_exclusive_put(emc->clk);
return 0;
}