linux-kernel - Re: [PATCH net-next v2 2/3] net: ethernet: ti: Register the RPMsg driver as network device

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Date: Tue, 4 Jun 2024 14:54:20 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Yojana Mallik <y-mallik@...com>
Cc: schnelle@...ux.ibm.com, wsa+renesas@...g-engineering.com,
	diogo.ivo@...mens.com, rdunlap@...radead.org, horms@...nel.org,
	vigneshr@...com, rogerq@...com, danishanwar@...com,
	pabeni@...hat.com, kuba@...nel.org, edumazet@...gle.com,
	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, srk@...com, rogerq@...nel.org,
	Siddharth Vadapalli <s-vadapalli@...com>
Subject: Re: [PATCH net-next v2 2/3] net: ethernet: ti: Register the RPMsg
 driver as network device

> >> +	u32 buff_slot_size;
> >> +	/* Base Address for Tx or Rx shared memory */
> >> +	u32 base_addr;
> >> +} __packed;
> > 
> > What do you mean by address here? Virtual address, physical address,
> > DMA address? And whos address is this, you have two CPUs here, with no
> > guaranteed the shared memory is mapped to the same address in both
> > address spaces.
> > 
> > 	Andrew
> 
> The address referred above is physical address. It is the address of Tx and Rx
> buffer under the control of Linux operating over A53 core. The check if the
> shared memory is mapped to the same address in both address spaces is checked
> by the R5 core.

u32 is too small for a physical address. I'm sure there are systems
with more than 4G of address space. Also, i would not assume both CPUs
map the memory to the same physical address.

	Andrew