On Mon, Feb 04, 2019 at 12:17:43PM +0000, David Laight wrote:
From: Jarkko Sakkinen
Sent: 01 February 2019 11:20 The current approach to read first 6 bytes from the response and then tail of the response, can cause the 2nd memcpy_fromio() to do an unaligned read (e.g. read 32-bit word from address aligned to a 16-bits), depending on how memcpy_fromio() is implemented. If this happens, the read will fail and the memory controller will fill the read with 1's.
To my mind memcpy_to/fromio() should only be used on IO addresses that are adequately like memory, and should be implemented in a way that that won't generate invalid bus cycles. Also memcpy_fromio() should also be allowed to do 'aligned' accesses that go beyond the ends of the required memory area.
...
- memcpy_fromio(buf, priv->rsp, 6);
- memcpy_fromio(buf, priv->rsp, 8); expected = be32_to_cpup((__be32 *) &buf[2]);
- if (expected > count || expected < 6)
- if (expected > count || expected < 8) return -EIO;
- memcpy_fromio(&buf[6], &priv->rsp[6], expected - 6);
- memcpy_fromio(&buf[8], &priv->rsp[8], expected - 8);
Why not just use readl() or readq() ?
Bound to generate better code.
For the first read can be done. The second read is of variable length.
/Jarkko