From: Samuel Holland samuel@sholland.org
The SID SRAM on at least some SoCs (A64 and D1) returns different values when read with bus cycles narrower than 32 bits. This is not immediately obvious, because memcpy_fromio() uses word-size accesses as long as enough data is being copied.
The vendor driver always uses 32-bit MMIO reads, so do the same here. This is faster than the register-based method, which is currently used as a workaround on A64. And it fixes the values returned on D1, where the SRAM method was being used.
The special case for the last word is needed to maintain .word_size == 1 for sysfs ABI compatibility, as noted previously in commit de2a3eaea552 ("nvmem: sunxi_sid: Optimize register read-out method").
Cc: stable@vger.kernel.org Fixes: 07ae4fde9efa ("nvmem: sunxi_sid: Add support for D1 variant") Tested-by: Heiko Stuebner heiko@sntech.de Signed-off-by: Samuel Holland samuel@sholland.org Signed-off-by: Srinivas Kandagatla srinivas.kandagatla@linaro.org --- drivers/nvmem/sunxi_sid.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c index 5750e1f4bcdb..92dfe4cb10e3 100644 --- a/drivers/nvmem/sunxi_sid.c +++ b/drivers/nvmem/sunxi_sid.c @@ -41,8 +41,21 @@ static int sunxi_sid_read(void *context, unsigned int offset, void *val, size_t bytes) { struct sunxi_sid *sid = context; + u32 word; + + /* .stride = 4 so offset is guaranteed to be aligned */ + __ioread32_copy(val, sid->base + sid->value_offset + offset, bytes / 4);
- memcpy_fromio(val, sid->base + sid->value_offset + offset, bytes); + val += round_down(bytes, 4); + offset += round_down(bytes, 4); + bytes = bytes % 4; + + if (!bytes) + return 0; + + /* Handle any trailing bytes */ + word = readl_relaxed(sid->base + sid->value_offset + offset); + memcpy(val, &word, bytes);
return 0; }