Message-ID: <718da090-bc58-0762-c901-cbbfc3b78d5f@huawei.com>
Date:   Sat, 4 Mar 2023 17:47:28 +0800
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Subject: Re: [PATCH 2/2] mailbox: pcc: Support shared interrupt for multiple
 subspaces
To:     Sudeep Holla <sudeep.holla@arm.com>
CC:     <robbiek@xsightlabs.com>, <linux-acpi@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <rafael@kernel.org>,
        <rafael.j.wysocki@intel.com>, <wanghuiqiang@huawei.com>,
        <zhangzekun11@huawei.com>, <wangxiongfeng2@huawei.com>,
        <tanxiaofei@huawei.com>, <guohanjun@huawei.com>,
        <xiexiuqi@huawei.com>, <wangkefeng.wang@huawei.com>,
        <huangdaode@huawei.com>
References: <20221016034043.52227-1-lihuisong@huawei.com>
 <20230216063653.1995-1-lihuisong@huawei.com>
 <20230216063653.1995-3-lihuisong@huawei.com>
 <20230301133626.gchca3fdaqijxwzq@bogus>
 <2a165476-2e96-17b1-a50b-c8749462e8a1@huawei.com>
 <20230302140216.m4m3452vexyrnuln@bogus>
 <020cc964-9938-7ebe-7514-125cd041bfcb@huawei.com>
 <20230303111407.zdgqdwqik4spnq2o@bogus>
From:   "lihuisong (C)" <lihuisong@huawei.com>
In-Reply-To: <20230303111407.zdgqdwqik4spnq2o@bogus>
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在 2023/3/3 19:14, Sudeep Holla 写道:
> On Fri, Mar 03, 2023 at 02:33:49PM +0800, lihuisong (C) wrote:
>> Sorry for my resend. Because I found that my last reply email is not in the
>> thread of this patch. I guess it may be send failed.
>>
>> 在 2023/3/2 22:02, Sudeep Holla 写道:
>>> No. I meant a comment saying it is not need since only one transfer can occur
>>> at a time and mailbox takes care of locking. So chan_in_use can be accessed
>>> without a lock.
>> Got it. Agreed.
> Thanks
already modify this comment as below.
>
>>>> For types no need this flag, it is always hard to understand and redundant
>>>> design.
>>> But does it matter ? You can even support shared interrupt for type 1&2.
>> BTW, type 1 subspaces do not support a level triggered platform interrupt as
>> no method is provided to clear the interrupt.
> Agreed but there is no harm using the flag, you can add a comment that it is
> useful only if shared interrupts are supported. That will imply it is dummy
> for type 1. I am avoiding too many type unnecessary checks especially in IRQ
> handler.

Understood.

>
>>> They support level interrupt, so we can add them too. I understand you can
>>> test only type 3, but this driver caters for all and the code must be generic
>>> as much as possible. I don't see any point in check for type 3 only. Only
>> I understand what you do.
>> But type 2 also supports the communication flow from OSPM to Platfrom.
>> In this case, this flag will get in the way of type 2.
>>
> How ?
It should be ok if all types except for type 3 do not check this flag in 
interrupt handle.
Namely, these types consider it as dummy, and do not use it, anywhere, 
Right?
>
>> Whether the interrupt belongs to a type2 channel is only determined by
>> the status field in Generic Communications Channel Shared Memory Region,
>> which is done in rx_callback of PCC client.
> Agreed, but do you see any issue using the flag even if it acts as dummy ?

I think it can work well if these types completely ignore this flag, like below.
what do you think?

-->8

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index ecd54f049de3..14405e99193d 100755
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -92,6 +92,13 @@ struct pcc_chan_reg {
   * @error: PCC register bundle for the error status register
   * @plat_irq: platform interrupt
   * @type: PCC subspace type
+ * @plat_irq_flags: platform interrupt flags
+ * @chan_in_use: this flag is used just to check if the interrupt needs
+ *             handling when it is shared. Since only one transfer can 
occur
+ *             at a time and mailbox takes care of locking, this flag 
can be
+ *             accessed without a lock. Note: the type only support the
+ *             communication from OSPM to Platform, like type3, use it, and
+ *             other types completely ignore it.
   */
  struct pcc_chan_info {
         struct pcc_mbox_chan chan;
@@ -102,6 +109,8 @@ struct pcc_chan_info {
         struct pcc_chan_reg error;
         int plat_irq;
         u8 type;
+       unsigned int plat_irq_flags;
+       bool chan_in_use;
  };

  #define to_pcc_chan_info(c) container_of(c, struct pcc_chan_info, chan)
@@ -225,6 +234,12 @@ 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_command_complete(struct pcc_chan_info *pchan,
                                       u64 cmd_complete_reg_val)
  {
@@ -277,6 +292,9 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
         int ret;

         pchan = chan->con_priv;
+       if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_MASTER_SUBSPACE &&
+           !pchan->chan_in_use)
+               return IRQ_NONE;

         ret = pcc_chan_reg_read(&pchan->cmd_complete, &val);
         if (ret)
@@ -302,9 +320,12 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
         /*
          * The PCC slave subspace channel needs to set the command 
complete bit
          * and ring doorbell after processing message.
+        *
+        * The PCC master subspace channel clears chan_in_use to free 
channel.
          */
         if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
                 pcc_send_data(chan, NULL);
+       pchan->chan_in_use = false;

         return IRQ_HANDLED;
  }
@@ -353,10 +374,13 @@ pcc_mbox_request_channel(struct mbox_client *cl, 
int subspace_id)
         spin_unlock_irqrestore(&chan->lock, flags);

         if (pchan->plat_irq > 0) {
+               unsigned long irqflags;
                 int rc;

-               rc = devm_request_irq(dev, pchan->plat_irq, pcc_mbox_irq, 0,
-                                     MBOX_IRQ_NAME, chan);
+               irqflags = pcc_chan_plat_irq_can_be_shared(pchan) ?
+                                       IRQF_SHARED | IRQF_ONESHOT : 0;
+               rc = devm_request_irq(dev, pchan->plat_irq, pcc_mbox_irq,
+                                     irqflags, MBOX_IRQ_NAME, chan);
                 if (unlikely(rc)) {
                         dev_err(dev, "failed to register PCC interrupt 
%d\n",
                                 pchan->plat_irq);
@@ -418,7 +442,11 @@ static int pcc_send_data(struct mbox_chan *chan, 
void *data)
         if (ret)
                 return ret;

-       return pcc_chan_reg_read_modify_write(&pchan->db);
+       ret = pcc_chan_reg_read_modify_write(&pchan->db);
+       if (!ret && pchan->plat_irq > 0)
+               pchan->chan_in_use = true;
+
+       return ret;
  }

  static const struct mbox_chan_ops pcc_chan_ops = {
@@ -501,6 +529,7 @@ static int pcc_parse_subspace_irq(struct 
pcc_chan_info *pchan,
                        pcct_ss->platform_interrupt);
                 return -EINVAL;
         }
+       pchan->plat_irq_flags = pcct_ss->flags;

         if (pcct_ss->header.type == 
ACPI_PCCT_TYPE_HW_REDUCED_SUBSPACE_TYPE2) {
                 struct acpi_pcct_hw_reduced_type2 *pcct2_ss = (void 
*)pcct_ss;
@@ -522,6 +551,12 @@ static int pcc_parse_subspace_irq(struct 
pcc_chan_info *pchan,
                                         "PLAT IRQ ACK");
         }

+       if (pcc_chan_plat_irq_can_be_shared(pchan) &&
+           !pchan->plat_irq_ack.gas) {
+               pr_err("PCC subspace has level IRQ with no ACK register\n");
+               return -EINVAL;
+       }
+
         return ret;
  }