On Tue, Feb 05, 2019 at 12:47:47PM +0200, Jarkko Sakkinen wrote: > On Tue, Feb 05, 2019 at 12:44:06PM +0200, Jarkko Sakkinen wrote: > > 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. > > Neither can be done to the first one, because readq() does > le64_to_cpu(). Shoud not do any conversions, only raw read. > So I'll just stick it to what we have. ATM tmp_crb is only used in LE architectures (x86 and ARM64), but I still hate to have hidden extra byte order conversions, even if they get compiled as nil ops. It is more wrong than to use memcpy_fromio(). /Jarkko
