by Matthias Brugger

[permalink] [raw]

Subject: Re: [PATCH v23 4/4] soc: mediatek: Add Mediatek CMDQ helper

On 15/08/2018 03:46, houlong wei wrote:
[...]
>> +
>> +static int cmdq_pkt_append_command(struct cmdq_pkt *pkt, enum cmdq_code code,
>> + u32 arg_a, u32 arg_b)
>> +{
>> + u64 *cmd_ptr;
>> +
>> + if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) {
>> + pkt->cmd_buf_size += CMDQ_INST_SIZE;
>> + return -ENOMEM;
>> + }
>> + cmd_ptr = pkt->va_base + pkt->cmd_buf_size;
>> + (*cmd_ptr) = (u64)((code << CMDQ_OP_CODE_SHIFT) | arg_a) << 32 | arg_b;
>> + pkt->cmd_buf_size += CMDQ_INST_SIZE;
>> +
>> + return 0;
>> +}
>> +
>> +int cmdq_pkt_write(struct cmdq_pkt *pkt, u32 value, u32 subsys, u32 offset)
>> +{
>> + u32 arg_a = (offset & CMDQ_ARG_A_WRITE_MASK) |
>> + (subsys << CMDQ_SUBSYS_SHIFT);
>> +
>> + return cmdq_pkt_append_command(pkt, CMDQ_CODE_WRITE, arg_a, value);
>> +}
>> +EXPORT_SYMBOL(cmdq_pkt_write);
>> +
>> +int cmdq_pkt_write_mask(struct cmdq_pkt *pkt, u32 value,
>> + u32 subsys, u32 offset, u32 mask)
>> +{
>> + u32 offset_mask = offset;
>> + int err;
>> +
>> + if (mask != 0xffffffff) {
>> + err = cmdq_pkt_append_command(pkt, CMDQ_CODE_MASK, 0, ~mask);
>> + WARN_ON(err < 0);

If we want to write out a warning to the kernel log, then we should but that in
the if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) from
cmdq_pkt_append_command to make it consistent between cmdq_pkt_write,
cmdq_pkt_write_mask and cmdq_pkt_finalize

Sorry, just saw this right now.

>> + offset_mask |= CMDQ_WRITE_ENABLE_MASK;
>> + }
>> +
>> + return cmdq_pkt_write(pkt, value, subsys, offset_mask);
>> +}
>> +EXPORT_SYMBOL(cmdq_pkt_write_mask);
>> +
>> +int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u32 event)
>> +{
>> + u32 arg_b;
>> +
>> + if (event >= CMDQ_MAX_EVENT)
>> + return -EINVAL;
>> +
>> + /*
>> + * WFE arg_b
>> + * bit 0-11: wait value
>> + * bit 15: 1 - wait, 0 - no wait
>> + * bit 16-27: update value
>> + * bit 31: 1 - update, 0 - no update
>> + */
>> + arg_b = CMDQ_WFE_UPDATE | CMDQ_WFE_WAIT | CMDQ_WFE_WAIT_VALUE;
>> +
>> + return cmdq_pkt_append_command(pkt, CMDQ_CODE_WFE, event, arg_b);
>> +}
>> +EXPORT_SYMBOL(cmdq_pkt_wfe);
>> +
>> +int cmdq_pkt_clear_event(struct cmdq_pkt *pkt, u32 event)
>> +{
>> + if (event >= CMDQ_MAX_EVENT)
>> + return -EINVAL;
>> +
>> + return cmdq_pkt_append_command(pkt, CMDQ_CODE_WFE, event,
>> + CMDQ_WFE_UPDATE);
>> +}
>> +EXPORT_SYMBOL(cmdq_pkt_clear_event);
>> +
>> +static int cmdq_pkt_finalize(struct cmdq_pkt *pkt)
>> +{
>> + int err;
>> +
>> + /* insert EOC and generate IRQ for each command iteration */
>> + err = cmdq_pkt_append_command(pkt, CMDQ_CODE_EOC, 0, CMDQ_EOC_IRQ_EN);
>> + WARN_ON(err < 0);

Should move into cmdq_pkt_append_command

>> +
>> + /* JUMP to end */
>> + err = cmdq_pkt_append_command(pkt, CMDQ_CODE_JUMP, 0, CMDQ_JUMP_PASS);
>> + WARN_ON(err < 0);

same here.

>> +
>> + return err;
>> +}
>> +
[...]

Regards,
Matthias

2018-09-27 10:32:32

by houlong wei

[permalink] [raw]

Subject: Re: [PATCH v23 4/4] soc: mediatek: Add Mediatek CMDQ helper

On Thu, 2018-09-27 at 15:50 +0800, Matthias Brugger wrote:
>
> On 27/09/2018 03:57, houlong wei wrote:
[...]
> >>> +
> >>> +static int cmdq_pkt_append_command(struct cmdq_pkt *pkt, enum cmdq_code code,
> >>> + u32 arg_a, u32 arg_b)
> >>> +{
> >>> + u64 *cmd_ptr;
> >>> +
> >>> + if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE > pkt->buf_size)) {
> >>> + pkt->cmd_buf_size += CMDQ_INST_SIZE;
> >>
> >> Why do we update the cmd_buf_size here?
> >
> > Because in developing phase of consumer driver, the consumer has to know
> > the real command buffer size after adding command failure. Then the
> > consumer will increase the size and run the cmdq flow (cmdq_pkt_create,
> > cmdq_pkt_write/wfe...) again. Finally, the consumer get the real size
> > and fix it.
> >
>
> But the consumer should know the size it needs for it's buffer and if not it
> should be able to decide on it's own how much space it needs. If he get's a
> -ENOMEM he implicitly knows that he has to increase the buf_size. Now the size
> depends on how many command he has pending and wasn't able to write to the cmdq_pkt.
>
> Regards,
> Matthias

The consumer doesn't know how to calculate the command buffer size that
he needs.
When the consumer driver is developing, he could ignore the return value
of cmdq_pkt_write and other command appending functions.
He can print the pkt->cmdq_buf_size after cmdq_pkt_flush() or
cmdq_pkt_flush_async() failure. Now he can get the buffer size he needs.

I copy your another comment here, so I can reply in one mail.
>>If we want to write out a warning to the kernel log, then we should
>>but that in the if (unlikely(pkt->cmd_buf_size + CMDQ_INST_SIZE
>>pkt->buf_size)) from cmdq_pkt_append_command to make it consistent
>>between cmdq_pkt_write, cmdq_pkt_write_mask and cmdq_pkt_finalize.

Thanks, I will move WARN_ON() into cmdq_pkt_append_command() before
returning -ENOMEM.

After your confirmation of the comments above, I will re-send a new
patch.