On 05/11/2019 11:05, Mark Brown wrote:
On Tue, Nov 05, 2019 at 10:58:39AM +0000, John Garry wrote:
On 04/11/2019 19:24, Mark Brown wrote:
On Tue, Nov 05, 2019 at 12:51:36AM +0800, John Garry wrote:
+ if (len) {
+ u32 val;
+
+ val = __raw_readl(host->regbase + CMD_DATABUF(words));
+
+ to += words * 4;
+ for (i = 0; i < len; i++, val >>= 8, to++)
+ *to = (u8)val;
+ }
+ } else {
+ for (i = 0; i < DIV_ROUND_UP(len, 4); i++) {
+ u32 val = __raw_readl(host->regbase + CMD_DATABUF(i));
+ int j;
The more usual pattern for these would be to do some unaligned accesses
for the start/end of the buffer to get to alignment and then transfer
the rest as aligned data.
Yeah, I understand you, but for that I would need to generate multiple
transactions in the driver, and I wanted to keep 1x transaction per
spi_controller_mem_ops.exec_op call.
Hi Mark,
So maybe I can do some trickery in my adjust_op_size method to generate
these multiple transactions: a. any unaligned start data b. the 32b-aligned
data b. unaligned end. I think that the HW should be able to handle that.
Right, that's what I was expecting.
So that should work for xfer data commands, but generally the read/write
reg commands in the SPI NOR layer would not use
spi_mem_adjust_op_size(), like spi-nor.c:spi_nor_read_id(), as an example.
For these, I should be able to guarantee start alignment (since the
buffer is kmalloc'ed), but not end alignment, so would still require
4-byte + single byte copies for these.
Thanks,
John
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