On 14/08/2022 18:36, Samuel Holland wrote:
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").
Missing Cc stable..
--srini
Fixes: 07ae4fde9efa ("nvmem: sunxi_sid: Add support for D1 variant")
Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx>
---
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;
}
