Re: [PATCH v9 6/9] i3c: master: Add driver for Cadence IP

[Arnd Bergmann <arnd@xxxxxxxx>]

On 10/24/18, Boris Brezillon <boris.brezillon@xxxxxxxxxxx> wrote:
> Hi Arnd,
>
> On Mon, 22 Oct 2018 15:34:01 +0200
> Boris Brezillon <boris.brezillon@xxxxxxxxxxx> wrote:
>
>
>> +
>> +static void cdns_i3c_master_rd_from_rx_fifo(struct cdns_i3c_master
>> *master,
>> +					    u8 *bytes, int nbytes)
>> +{
>> +	readsl(master->regs + RX_FIFO, bytes, nbytes / 4);
>
> Vitor reported a problem with readsl(): this function expects the 2nd
> argument to be aligned on 32-bit, which is not guaranteed here. Unless
> you see a better solution, I'll switch back to a loop doing:
>
> 	for (i = 0; i < nbytes; i += 4) {
> 		u32 tmp = __raw_readl(...);
> 		memcpy(bytes + i, &tmp,
> 		       nbytes - i  > 4 ? 4 : nbytes - i);
> 	}

Could we maybe mandate that the buffer itself must be aligned here?
What would be a reason why we see an unaligned target buffer?

The open-coded loop should generally work (maybe a little slower),
but it does seem error-prone to use __raw_readl() in general.

      Arnd