On 3/16/23 10:57, Charles Keepax wrote:
Currently issuing a sdw_nread/nwrite_no_pm across a page boundary will silently fail to write correctly as nothing updates the page registers, meaning the same page of the chip will get rewritten with each successive page of data.
As the sdw_msg structure contains page information it seems reasonable that a single sdw_msg should always be within one page. It is also mostly simpler to handle the paging at the bus level rather than each master having to handle it in their xfer_msg callback.
As such add handling to the bus code to split up a transfer into multiple sdw_msg's when they go across page boundaries.
This sounds good but we need to clarify that the multiple sdw_msg's will not necessarily be sent one after the other, the msg_lock is held in the sdw_transfer() function, so there should be no expectation that e.g. one big chunk of firmware code can be sent without interruption.
I also wonder if we should have a lower bar than the page to avoid hogging the bus with large read/write transactions. If there are multiple devices on the same link and one of them signals an alert status while a large transfer is on-going, the alert handling will mechanically be delayed by up to a page - that's 32k reads/writes, isn't it?
Signed-off-by: Charles Keepax ckeepax@opensource.cirrus.com
drivers/soundwire/bus.c | 47 +++++++++++++++++++++++------------------ 1 file changed, 26 insertions(+), 21 deletions(-)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 3c67266f94834..bdd251e871694 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -386,37 +386,42 @@ int sdw_fill_msg(struct sdw_msg *msg, struct sdw_slave *slave,
- Read/Write IO functions.
*/
-int sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val) +static int sdw_ntransfer_no_pm(struct sdw_slave *slave, u32 addr, u8 flags,
size_t count, u8 *val){ struct sdw_msg msg;
- size_t size; int ret;
- ret = sdw_fill_msg(&msg, slave, addr, count,
slave->dev_num, SDW_MSG_FLAG_READ, val);- if (ret < 0)
return ret;
- while (count) {
// Only handle bytes up to next page boundarysize = min(count, (SDW_REGADDR + 1) - (addr & SDW_REGADDR));
- ret = sdw_transfer(slave->bus, &msg);
- if (slave->is_mockup_device)
ret = 0;- return ret;
ret = sdw_fill_msg(&msg, slave, addr, size, slave->dev_num, flags, val);if (ret < 0)return ret;ret = sdw_transfer(slave->bus, &msg);if (ret < 0 && !slave->is_mockup_device)return ret;addr += size;val += size;count -= size;- }
- return 0;
+}
+int sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val) +{
- return sdw_ntransfer_no_pm(slave, addr, SDW_MSG_FLAG_READ, count, val);
} EXPORT_SYMBOL(sdw_nread_no_pm);
int sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val) {
- struct sdw_msg msg;
- int ret;
- ret = sdw_fill_msg(&msg, slave, addr, count,
slave->dev_num, SDW_MSG_FLAG_WRITE, (u8 *)val);- if (ret < 0)
return ret;- ret = sdw_transfer(slave->bus, &msg);
- if (slave->is_mockup_device)
ret = 0;- return ret;
- return sdw_ntransfer_no_pm(slave, addr, SDW_MSG_FLAG_WRITE, count, (u8 *)val);
} EXPORT_SYMBOL(sdw_nwrite_no_pm);