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SubjectRe: [RFC V2] ACPI: PCC: Support shared interrupt for multiple subspaces
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在 2022/11/22 21:46, Sudeep Holla 写道:
> On Tue, Nov 22, 2022 at 11:30:51AM +0800, Huisong Li wrote:
>> If the platform acknowledge interrupt is level triggered, then it can
>> be shared by multiple subspaces provided each one has a unique platform
>> interrupt ack preserve and ack set masks.
>>
>> If it can be shared, then we can request the irq with IRQF_SHARED and
>> IRQF_ONESHOT flags. The first one indicating it can be shared and the
>> latter one to keep the interrupt disabled until the hardirq handler
>> finished.
>>
>> Further, since there is no way to detect if the interrupt is for a given
>> channel as the interrupt ack preserve and ack set masks are for clearing
>> the interrupt and not for reading the status, we need a way to identify
>> if the given channel is in use and expecting the interrupt.
>>
>> The way and differences of identification interrupt of each types for a
>> given channel are as follows:
>> 1) type0, type1 and type5: do not support shared level triggered interrupt.
>> 2) type2: whether the interrupt belongs to a given channel is detected
>> based on the status field in Generic Communications Channel
>> Shared Memory Region during calling rx_callback in PCC client
>> code.
>> 3) type3: use the command complete register and chan_in_use flag to control
>> 4) type4: use the command complete register and need to set the
>> corresponding bit of salve subspace to 1 by default in platform.
>>
>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
>> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> While I am aware that there are parts of this patch that I have suggested or
> was part of the discussion, it doesn't mean you can add my sign-off without
> my consent. You have introduced new things here which I haven't seen or
> agreed to, so this sign-off is completely meaningless and wrong. Please
> don't do that in the future.
Sorry, I got it. I'll remove this sign-off. Thank you for reminding.
>
>> Signed-off-by: Robbie King <robbiek@xsightlabs.com>
>> ---
>> -v2: don't use platform interrupt ack register to identify if the given
>> channel should respond interrupt.
>>
>> ---
>> drivers/mailbox/pcc.c | 130 +++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 116 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
>> index 3c2bc0ca454c..674e214d64d1 100644
>> --- a/drivers/mailbox/pcc.c
>> +++ b/drivers/mailbox/pcc.c
>> @@ -80,6 +80,13 @@ struct pcc_chan_reg {
>> u64 status_mask;
>> };
>>
>> +enum pcc_chan_mesg_dir {
>> + PCC_ONLY_AP_TO_SCP,
>> + PCC_ONLY_SCP_TO_AP,
> AP and SCP sounds very specific to your platform. The ACPI PCC spec doesn't
> talk about these or use these terminology IIUC. You need to refer AP as OSPM
> and SCP as platform.
ok
>
>> + PCC_BIDIRECTIONAL,
> Again I need to check about this in the specification.
>
>> + PCC_DIR_UNKNOWN,
>> +};
>> +
>> /**
>> * struct pcc_chan_info - PCC channel specific information
>> *
>> @@ -91,6 +98,10 @@ struct pcc_chan_reg {
>> * @cmd_update: PCC register bundle for the command complete update register
>> * @error: PCC register bundle for the error status register
>> * @plat_irq: platform interrupt
>> + * @plat_irq_flags: platform interrupt flags
>> + * @chan_in_use: flag indicating whether the channel is in use or not when use
>> + * platform interrupt, and only use it for PCC_ONLY_AP_TO_SCP
>> + * @mesg_dir: direction of message transmission supported by the channel
>> */
>> struct pcc_chan_info {
>> struct pcc_mbox_chan chan;
>> @@ -100,12 +111,17 @@ struct pcc_chan_info {
>> struct pcc_chan_reg cmd_update;
>> struct pcc_chan_reg error;
>> int plat_irq;
>> + unsigned int plat_irq_flags;
>> + bool chan_in_use;
>> + u8 mesg_dir;
>> };
>>
>> #define to_pcc_chan_info(c) container_of(c, struct pcc_chan_info, chan)
>> static struct pcc_chan_info *chan_info;
>> static int pcc_chan_count;
>>
>> +static int pcc_send_data(struct mbox_chan *chan, void *data);
>> +
>> /*
>> * PCC can be used with perf critical drivers such as CPPC
>> * So it makes sense to locally cache the virtual address and
>> @@ -221,6 +237,47 @@ static int pcc_map_interrupt(u32 interrupt, u32 flags)
>> return acpi_register_gsi(NULL, interrupt, trigger, polarity);
>> }
>>
>> +static bool pcc_chan_plat_irq_can_be_shared(struct pcc_chan_info *pchan)
>> +{
>> + return (pchan->plat_irq_flags & ACPI_PCCT_INTERRUPT_MODE) ==
>> + ACPI_LEVEL_SENSITIVE;
>> +}
>> +
>> +static bool pcc_chan_need_rsp_irq(struct pcc_chan_info *pchan,
>> + u64 cmd_complete_reg_val)
>> +{
>> + bool need_rsp;
>> +
>> + if (!pchan->cmd_complete.gas)
>> + return true;
>> +
>> + cmd_complete_reg_val &= pchan->cmd_complete.status_mask;
>> +
>> + switch (pchan->mesg_dir) {
>> + case PCC_ONLY_AP_TO_SCP:
>> + /*
>> + * For the communication from AP to SCP, if this channel is in
>> + * use, command complete bit is 1 indicates that the command
>> + * being executed has been completed.
>> + */
>> + need_rsp = cmd_complete_reg_val != 0;
>> + break;
>> + case PCC_ONLY_SCP_TO_AP:
>> + /*
>> + * For the communication from SCP to AP, if this channel is in
>> + * use, command complete bit is 0 indicates that the bit has
>> + * been cleared and AP should response the interrupt.
>> + */
>> + need_rsp = cmd_complete_reg_val == 0;
>> + break;
>> + default:
>> + need_rsp = true;
>> + break;
>> + }
>> +
>> + return need_rsp;
>> +}
>> +
>> /**
>> * pcc_mbox_irq - PCC mailbox interrupt handler
>> * @irq: interrupt number
>> @@ -232,37 +289,54 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
>> {
>> struct pcc_chan_info *pchan;
>> struct mbox_chan *chan = p;
>> + static irqreturn_t rc;
>> u64 val;
>> int ret;
>>
>> pchan = chan->con_priv;
>> + if (pchan->mesg_dir == PCC_ONLY_AP_TO_SCP && !pchan->chan_in_use)
>> + return IRQ_NONE;
>>
>> ret = pcc_chan_reg_read(&pchan->cmd_complete, &val);
>> if (ret)
>> return IRQ_NONE;
>> + if (!pcc_chan_need_rsp_irq(pchan, val))
>> + return IRQ_NONE;
>>
> Not sure the login in pcc_chan_need_rsp_irq works for type1/2 channels
> or am I missing something.
First of all, type 1 subspaces do not support a level triggered platform
interrupt
as no method is provided to clear the interrupt. Secondly, because there
is no
command complete register, pcc_chan_need_rsp_irq return true for type2
channels.
and the interrupt for type2 channels have to be identified in the
rx_callback of
PCC client. Generally, the rx_callback of PCC client based on type2
channel should
do it. I found that some drivers already do that, such as,
xgene-slimpro-hwmon and
xgene-slimpro-i2c.
>
>> - if (val) { /* Ensure GAS exists and value is non-zero */
>> - val &= pchan->cmd_complete.status_mask;
>> - if (!val)
>> - return IRQ_NONE;
>> + ret = pcc_chan_reg_read(&pchan->error, &val);
>> + if (ret) {
>> + rc = IRQ_NONE;
>> + goto out;
>> }
>>
>> - ret = pcc_chan_reg_read(&pchan->error, &val);
>> - if (ret)
>> - return IRQ_NONE;
>> val &= pchan->error.status_mask;
>> if (val) {
>> val &= ~pchan->error.status_mask;
>> pcc_chan_reg_write(&pchan->error, val);
>> - return IRQ_NONE;
>> + rc = IRQ_NONE;
>> + goto out;
>> }
>>
>> - if (pcc_chan_reg_read_modify_write(&pchan->plat_irq_ack))
>> - return IRQ_NONE;
>> + if (pcc_chan_reg_read_modify_write(&pchan->plat_irq_ack)) {
>> + rc = IRQ_NONE;
>> + goto out;
>> + }
>>
>> mbox_chan_received_data(chan, NULL);
>> + /*
>> + * For slave subspace, need to set the command complete bit and ring
>> + * doorbell after processing message.
>> + */
>> + if (pchan->mesg_dir == PCC_ONLY_SCP_TO_AP)
>> + pcc_send_data(chan, NULL);
>> +
>> + rc = IRQ_HANDLED;
>>
> Also I think it is better to split the support into 2 different patches.
> Add type 4 channel interrupt handling support and then handle interrupt
> sharing or vice-versa. I am struggling to follow this. I would also avoid
> goto in a interrupt handler unless absolutely necessary.
Yes. I will split it in next version.

I'm actually struggling with what value this interrupt handler should
return when
fail to read/write register if a channel need to respond the interrupt
and what to
do for the chan_in_use flag. What do you think?
>

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