On 7/19/2013 7:17 PM, Seungwon Jeon wrote:
On Thu, July 18, 2013, Sujit Reddy Thumma wrote:
+ * ufshcd_wait_for_register - wait for register value to change
+ * @hba - per-adapter interface
+ * @reg - mmio register offset
+ * @mask - mask to apply to read register value
+ * @val - wait condition
+ * @interval_us - polling interval in microsecs
+ * @timeout_ms - timeout in millisecs
+ *
+ * Returns final register value after iteration
+ */
+static u32 ufshcd_wait_for_register(struct ufs_hba *hba, u32 reg, u32 mask,
+ u32 val, unsigned long interval_us, unsigned long timeout_ms)
I feel like this function's role is to wait for clearing register (specially, doorbells).
If you really don't intend to apply other all register, I think it would better to change the
function name.
ex> ufshcd_wait_for_clear_doorbell or ufshcd_wait_for_clear_reg?
Although, this API is introduced in this patch and used only for
clearing the doorbell, I have intentionally made it generic to avoid
duplication of wait condition code in future (not just clearing but
also for setting a bit). For example, when we write to HCE.ENABLE we
wait for it turn to 1.
And if you like it, it could be more simple like below
static bool ufshcd_wait_for_clear_reg(struct ufs_hba *hba, u32 reg, u32 mask,
unsigned long interval_us,
unsigned int timeout_ms)
{
unsigned long timeout = jiffies + msecs_to_jiffies(timeout_ms);
Jiffies on 100Hz systems have minimum granularity of 10ms. So we really
wait for more 10ms even though the timeout_ms < 10ms.
Yes. Real timeout depends on system.
But normally actual wait will be maintained until 'ufshcd_readl' is done.
Timeout is valid for failure case. If we don't need to apply a strict timeout value, it's not bad.
Hmm.. make sense. Will take care in the next patchset.
/* wakeup within 50us of expiry */
const unsigned int expiry = 50;
while (ufshcd_readl(hba, reg) & mask) {
usleep_range(interval_us, interval_us + expiry);
if (time_after(jiffies, timeout)) {
if (ufshcd_readl(hba, reg) & mask)
return false;
I really want the caller to decide on what to do after the timeout.
This helps in error handling cases where we try to clear off the entire
door-bell register but only a few of the bits are cleared after timeout.
I don't know what we can do with the report of the partial success on clearing bit.
It's just failure case. Isn't enough with false/true?
The point is, if a bit can't be cleared it can be regarded as a
permanent failure (only for that request), otherwise, it can be
retried with the same tag value.
else
return true;
}
}
return true;
}
+{
+ u32 tmp;
+ ktime_t start;
+ unsigned long diff;
+
+ tmp = ufshcd_readl(hba, reg);
+
+ if ((val & mask) != val) {
+ dev_err(hba->dev, "%s: Invalid wait condition 0x%x\n",
+ __func__, val);
+ goto out;
+ }
+
+ start = ktime_get();
+ while ((tmp & mask) != val) {
+ /* wakeup within 50us of expiry */
+ usleep_range(interval_us, interval_us + 50);
+ tmp = ufshcd_readl(hba, reg);
+ diff = ktime_to_ms(ktime_sub(ktime_get(), start));
+ if (diff > timeout_ms) {
+ tmp = ufshcd_readl(hba, reg);
+ break;
+ }
+ }
+out:
+ return tmp;
+}
+
..
+static int
+ufshcd_clear_cmd(struct ufs_hba *hba, int tag)
+{
+ int err = 0;
+ unsigned long flags;
+ u32 reg;
+ u32 mask = 1 << tag;
+
+ /* clear outstanding transaction before retry */
+ spin_lock_irqsave(hba->host->host_lock, flags);
+ ufshcd_utrl_clear(hba, tag);
+ spin_unlock_irqrestore(hba->host->host_lock, flags);
+
+ /*
+ * wait for for h/w to clear corresponding bit in door-bell.
+ * max. wait is 1 sec.
+ */
+ reg = ufshcd_wait_for_register(hba,
+ REG_UTP_TRANSFER_REQ_DOOR_BELL,
+ mask, 0, 1000, 1000);
4th argument should be (~mask) instead of '0', right?
True, but not really for this implementation. It breaks the check in
in wait_for_register -
if ((val & mask) != val)
dev_err(...);
Hmm, it seems complicated to use.
Ok. Is right the following about val as 4th argument?
- clear: val should be '0' regardless corresponding bit.
- set: val should be same with mask.
If the related comment is added, it will be helpful.
Thinking again it looks like it is complicated. How about changing
the check to -
val = val & mask; /* ignore the bits we don't intend to wait on */
while (ufshcd_readl() & mask != val) {
sleep
}
Usage will be ~mask for clearing the bits, mask for setting the bits
in the fourth argument.
Ok.
It's better for the caller.
Actually, mask value involves the corresponding bit to be cleared.
So, 4th argument may be unnecessary.
As I described above, the wait_for_register can also be used to
check if the value is set or not. In which case, we need 4th argument.
+ if ((reg & mask) == mask)
+ err = -ETIMEDOUT;
Also, checking the result can be involved in ufshcd_wait_for_register.
Any comment?
Sorry I missed this. But the point was the same. To make
wait_for_register() just to wait a definite time and not return any
error condition when the bits don't turn as expected.
Comparing reg with mask can be done in 'ufshcd_wait_for_register' commonly.
Currently the caller do the same.
Hmm.. you don't seem to agree to my point earlier mentioned
">>>> I really want the caller to decide on what to do after the timeout.
>>>> This helps in error handling cases where we try to clear off the
entire
>>>> door-bell register but only a few of the bits are cleared after
timeout.
>>> I don't know what we can do with the report of the partial success
on clearing bit.
>>> It's just failure case. Isn't enough with false/true?
>>
>> The point is, if a bit can't be cleared it can be regarded as a
>> permanent failure (only for that request), otherwise, it can be
>> retried with the same tag value."
Since there is no real use case as of now. I will move the error check
to the wait_for_register.
--
Regards,
Sujit
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