Messages in this thread | | | Subject | Re: [PATCH] firmware: arm_scmi: Pass shmem address to SMCCC call | From | Paul Murphy <> | Date | Fri, 17 Jul 2020 15:00:16 +0100 |
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Hi Florian
On 7/16/20 20:57, Florian Fainelli wrote:
>>> >>> Given that the kernel must somehow reserve this memory as a shared >>> memory area for obvious reasons, and the trusted firmware must also >>> ensure it treats this memory region with specific permissions in its >>> translation regime, does it really make sense to give that much >>> flexibility? >> >> Well, the trusted firmware might reserve a bigger region to be used for >> other service as well. In other words, the MMU of TF-A is not necessary >> specifically set up for this region, but, possibly, for a bigger >> general shared region. > > But presumably the Linux shared memory area should be mapped in a > slightly different way than >
Sorry - could you clarify what you mean by that?
Just checking if we are doing everything correctly.
I didn't understand that there is a connection between the TF-A MMU tables for this region and the normal world MMU tables?
For example:
TF-A may map physical address range: 0x0 -> 0x400_000 as 'normal' memory for various purposes.
Linux SCMI driver could map physical address range, eg: 0x300_000 -> 0x301_000 as IO memory for mailbox purpose only.
Is there any issue here?
Regards,
Paul
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