On 4/19/24 15:41, Cédric Le Goater wrote:
On 4/16/24 11:18, Jamin Lin wrote:
DMA length is from 1 byte to 32MB for AST2600 and AST10x0
and DMA length is from 4 bytes to 32MB for AST2500.
In other words, if "R_DMA_LEN" is 0, it should move at least 1 byte
data for AST2600 and AST10x0 and 4 bytes data for AST2500.
To support all ASPEED SOCs, adds dma_start_length parameter to store
the start length, add helper routines function to compute the dma length
and update DMA_LENGTH mask to "1FFFFFF" to fix dma moving
incorrect data length issue.
OK. There are two problems to address, the "zero" length transfer and
the DMA length unit, which is missing today. Newer SoC use a 1 bit / byte
and older ones, AST2400 and AST2500, use 1 bit / 4 bytes.
We can introduce a AspeedSMCClass::dma_len_unit and rework the loop to :
do {
....
if (s->regs[R_DMA_LEN]) {
s->regs[R_DMA_LEN] -= 4 / asc->dma_len_unit;
}
} while (s->regs[R_DMA_LEN]);
It should fix the current implementation.
I checked what FW is doing on a QEMU ast2500-evb machine :
U-Boot 2019.04-v00.04.12 (Sep 29 2022 - 10:40:37 +0000)
...
Loading Kernel Image ... aspeed_smc_write @0x88 size 4: 0x80001000
aspeed_smc_write @0x84 size 4: 0x20100130
aspeed_smc_write @0x8c size 4: 0x3c6770
aspeed_smc_write @0x80 size 4: 0x1
aspeed_smc_dma_rw read flash:@0x00100130 dram:@0x1000 size:0x003c6774
aspeed_smc_read @0x8 size 4: 0x800
aspeed_smc_write @0x80 size 4: 0x0
OK
Loading Ramdisk to 8fef2000, end 8ffff604 ... aspeed_smc_write @0x88
size 4: 0x8fef2000
aspeed_smc_write @0x84 size 4: 0x204cdde0
aspeed_smc_write @0x8c size 4: 0x10d604
aspeed_smc_write @0x80 size 4: 0x1
aspeed_smc_dma_rw read flash:@0x004cdde0 dram:@0xfef2000 size:0x0010d608
aspeed_smc_read @0x8 size 4: 0x800
aspeed_smc_write @0x80 size 4: 0x0
OK
Loading Device Tree to 8fee7000, end 8fef135e ... aspeed_smc_write @0x88
size 4: 0x8fee7000
aspeed_smc_write @0x84 size 4: 0x204c69b4
aspeed_smc_write @0x8c size 4: 0x7360
aspeed_smc_write @0x80 size 4: 0x1
aspeed_smc_dma_rw read flash:@0x004c69b4 dram:@0xfee7000 size:0x00007364
aspeed_smc_read @0x8 size 4: 0x800
aspeed_smc_write @0x80 size 4: 0x0
OK
Starting kernel ...
It seems that the R_DMA_LEN register is set by FW without taking
into account the length unit ( bit / 4 bytes). Would you know why ?
If I change the model to match 1 bit / 4 bytes unit of the R_DMA_LEN
register. Linux fails to boot. I didn't dig further and this is
something we need to understand before committing.
I don't think this is necessary to add a Fixes tag because the problem
has been there for ages and no one reported it. Probably because the
only place DMA transfers are used is in U-Boot and transfers have a
non-zero length.
Currently, only supports dma length 4 bytes aligned.
Is this 4 bytes alignment new for the AST2700 or is this something
you added because the mask of DMA_LENGTH is now relaxed to match
all addresses ?
#define DMA_LENGTH(val) ((val) & 0x01FFFFFF)
Thanks,
C.
