Re: CPM_UART should allocate DPRAM for SMCx parameter RAM on MPC82xx

On Wed, 7 Jun 2006 14:34:08 +0200
Laurent Pinchart [off-list ref] wrote:

Hi everybody,

the move to platform devices introduced a bug in the CPM_UART SMC driver.

Unlike SCC and FCC, the SMC parameter ram is not at a fixed location. A 
pointer to the parameter ram is instead stored at PROFF_SMCx_BASE.

The SMC platform device resources (in arch/ppc/syslib/pq2_devices.c) reserves 
the memory resource PROFF_SMCx_BASE - PROFF_SMCx_BASE+1. The CPM UART driver 
considers that value as the SMC parameter ram offset. It should instead 
allocate 64 bytes (on a 64 bytes boundary) of DPRAM for its parameter ram, 
and store the offset at PROFF_SMCx_BASE. 

I'm not sure how to fix the problem as it seems that the platform device 
support is not complete yet (cpm_uart_init_portdesc is still used to 
initialize the console). A possible workaround is to set the pram resource to 
0x0000-0x003f and 0x0040-0x007f instead of 0x87fc-0x87fd and 0x88fc-0x88fd 
for SMC1 and SMC2. This will not work if cpm_uart_init_portdesc is not 
called.

No, pdev support for cpm uart is complete and works for every board I have handy, both 8xx and 82xx.
8xx use SMC stuff and are ok, so I suppose the issue got inside because this is first case we head with combination of pq2/smc. 

init_portedsc is called in compatibility mode only, when driver was
unable to locate platform device (early_uart_get_pdev call). The
offsets are definitely odd - we should count the proper values (as it
was done for 8xx - offset from immr where pram will be located that
is). So, pq2_devices should be fixed, as well as bsp code should
provide early_uart_get_pdev call (see 8272 as reference).

-- 
Sincerely, 
Vitaly