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

On Wed, 7 Jun 2006 15:39:57 +0200
Laurent Pinchart [off-list ref] wrote:

quoted

quoted

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).

From my understanding, SMC pram should be allocated, and its offset should be 
stored at PROFF_SMCx_BASE. pq2_devices returns the PRFF_SMCx_BASE resource, 
and the CPM UART driver should use cpm_dpalloc to allocate the parameter RAM. 
Is that right ? If so, where should I allocate memory (and where should I 
free it) in the CPM UART driver ?

As I said, SMC offsets relative to pram things are screwed for PQ2.
That needs to be fixed. It is assumed, that for each SMC ready-for-use offset should be defined in pram resource (as for 8xx). There is no need to dpalloc/dpfree because the idea is that pram thing should be fixed to prevent confusion. So the odd offset for SMC devices in pq2_devices.c should be replaced with correct values (which should be dpram_start+PROFF_SMCx - have a look at 8xx as reference)

-- 
Sincerely, 
Vitaly