| Message ID | 20201008143722.21888-4-etienne.carriere@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/5] firmware: arm_scmi: always initialize protocols | expand |
On Thu, Oct 08, 2020 at 04:37:21PM +0200, Etienne Carriere wrote: > There is no reason for the smc transport to restrict itself to a 1 > message pool. More can be allocated, messages are copied from/to the > shared memory only on SMC exit/entry hence SCMI driver can play with > several messages. > > Use value of 20 to mimic mailbox transport implementation. What is the need to mimic ? > Any high value could fit. This should be something configurable. Why not 10 or 100 ? I see any value other than 1 is useless as we lock the channel in send_message and we don't maintain a queue like mailbox.
On Thu, 8 Oct 2020 at 23:11, Sudeep Holla <sudeep.holla@arm.com> wrote: > > On Thu, Oct 08, 2020 at 04:37:21PM +0200, Etienne Carriere wrote: > > There is no reason for the smc transport to restrict itself to a 1 > > message pool. More can be allocated, messages are copied from/to the > > shared memory only on SMC exit/entry hence SCMI driver can play with > > several messages. > > > > Use value of 20 to mimic mailbox transport implementation. > > What is the need to mimic ? I had to pick a value. I can't say whether 2, 5 or 20 is better. I looks how the mailbox transport did and used the same value as it seemed reasonable regarding its memory cost. > > > Any high value could fit. This should be something configurable. > > Why not 10 or 100 ? I see any value other than 1 is useless as we lock > the channel in send_message and we don't maintain a queue like mailbox. I'll check again. Playing with SCMI voltage domain [1], it happens that I needed several preallocated message buffers unless what regulators fail to be probed. [1] https://lkml.org/lkml/2020/10/5/1341 Regards, etienne > > -- > Regards, > Sudeep
On Fri, Oct 09, 2020 at 02:43:31PM +0200, Etienne Carriere wrote: > On Thu, 8 Oct 2020 at 23:11, Sudeep Holla <sudeep.holla@arm.com> wrote: > > > > On Thu, Oct 08, 2020 at 04:37:21PM +0200, Etienne Carriere wrote: > > > There is no reason for the smc transport to restrict itself to a 1 > > > message pool. More can be allocated, messages are copied from/to the > > > shared memory only on SMC exit/entry hence SCMI driver can play with > > > several messages. > > > > > > Use value of 20 to mimic mailbox transport implementation. > > > > What is the need to mimic ? > > I had to pick a value. I can't say whether 2, 5 or 20 is better. > I looks how the mailbox transport did and used the same value > as it seemed reasonable regarding its memory cost. > > > > > > Any high value could fit. This should be something configurable. > > > > Why not 10 or 100 ? I see any value other than 1 is useless as we lock > > the channel in send_message and we don't maintain a queue like mailbox. > > I'll check again. > Playing with SCMI voltage domain [1], it happens that I needed several > preallocated message buffers unless what regulators fail to be probed. I may be missing something but I can't see how, we simply block in send_message while mailbox has a queue of 20 which is why it has 20 there. The issue you are seeing could be different. Let me know if I am missing something.
On Fri, Oct 09, 2020 at 04:17:52PM +0100, Sudeep Holla wrote: > On Fri, Oct 09, 2020 at 02:43:31PM +0200, Etienne Carriere wrote: > > On Thu, 8 Oct 2020 at 23:11, Sudeep Holla <sudeep.holla@arm.com> wrote: > > > > > > On Thu, Oct 08, 2020 at 04:37:21PM +0200, Etienne Carriere wrote: > > > > There is no reason for the smc transport to restrict itself to a 1 > > > > message pool. More can be allocated, messages are copied from/to the > > > > shared memory only on SMC exit/entry hence SCMI driver can play with > > > > several messages. > > > > > > > > Use value of 20 to mimic mailbox transport implementation. > > > > > > What is the need to mimic ? > > > > I had to pick a value. I can't say whether 2, 5 or 20 is better. > > I looks how the mailbox transport did and used the same value > > as it seemed reasonable regarding its memory cost. > > > > > > > > > Any high value could fit. This should be something configurable. > > > > > > Why not 10 or 100 ? I see any value other than 1 is useless as we lock > > > the channel in send_message and we don't maintain a queue like mailbox. > > > > I'll check again. > > Playing with SCMI voltage domain [1], it happens that I needed several > > preallocated message buffers unless what regulators fail to be probed. > > > I may be missing something but I can't see how, we simply block in > send_message while mailbox has a queue of 20 which is why it has 20 there. > > The issue you are seeing could be different. Let me know if I am missing > something. > OK, I gave this some thought and realise that in-order to allow multiple requests simultaneously, we do need this value > 1. I will take this and make some tweaks to the commit log to indicate the same.
On Mon, 12 Oct 2020 at 10:57, Sudeep Holla <sudeep.holla@arm.com> wrote: > > On Fri, Oct 09, 2020 at 04:17:52PM +0100, Sudeep Holla wrote: > > On Fri, Oct 09, 2020 at 02:43:31PM +0200, Etienne Carriere wrote: > > > On Thu, 8 Oct 2020 at 23:11, Sudeep Holla <sudeep.holla@arm.com> wrote: > > > > > > > > On Thu, Oct 08, 2020 at 04:37:21PM +0200, Etienne Carriere wrote: > > > > > There is no reason for the smc transport to restrict itself to a 1 > > > > > message pool. More can be allocated, messages are copied from/to the > > > > > shared memory only on SMC exit/entry hence SCMI driver can play with > > > > > several messages. > > > > > > > > > > Use value of 20 to mimic mailbox transport implementation. > > > > > > > > What is the need to mimic ? > > > > > > I had to pick a value. I can't say whether 2, 5 or 20 is better. > > > I looks how the mailbox transport did and used the same value > > > as it seemed reasonable regarding its memory cost. > > > > > > > > > > > > Any high value could fit. This should be something configurable. > > > > > > > > Why not 10 or 100 ? I see any value other than 1 is useless as we lock > > > > the channel in send_message and we don't maintain a queue like mailbox. > > > > > > I'll check again. > > > Playing with SCMI voltage domain [1], it happens that I needed several > > > preallocated message buffers unless what regulators fail to be probed. > > > > > > I may be missing something but I can't see how, we simply block in > > send_message while mailbox has a queue of 20 which is why it has 20 there. > > > > The issue you are seeing could be different. Let me know if I am missing > > something. > > > > OK, I gave this some thought and realise that in-order to allow multiple > requests simultaneously, we do need this value > 1. I will take this > and make some tweaks to the commit log to indicate the same. > Thanks for the feedback. I planned to look back which value would really make sense. Whatever, feel free to tweak or change this proposal. Regards, etienne > -- > Regards, > Sudeep
diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c index 1a03c3ec0230..82a82a5dc86a 100644 --- a/drivers/firmware/arm_scmi/smc.c +++ b/drivers/firmware/arm_scmi/smc.c @@ -149,6 +149,6 @@ static const struct scmi_transport_ops scmi_smc_ops = { const struct scmi_desc scmi_smc_desc = { .ops = &scmi_smc_ops, .max_rx_timeout_ms = 30, - .max_msg = 1, + .max_msg = 20, .max_msg_size = 128, };
There is no reason for the smc transport to restrict itself to a 1 message pool. More can be allocated, messages are copied from/to the shared memory only on SMC exit/entry hence SCMI driver can play with several messages. Use value of 20 to mimic mailbox transport implementation. Any high value could fit. This should be something configurable. Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org> Cc: Peng Fan <peng.fan@nxp.com> --- drivers/firmware/arm_scmi/smc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)