On 2017/8/4 14:38, Adrian Hunter wrote:
On 04/08/17 05:08, Shawn Lin wrote:
Per the SD physical layer simplified specification V4.10,
section 4.6.2, CSD version 1.0 SD card should use taac, nsac
and r2w_factor for calculating the data access time. But the
taac and nsac for SDHC(CSD version 2.0) are always fixed and
the software should use the recommended value for timeout. When
parsing the CSD, we sanely set them to zero for SDHC(CSD version
2.0), all the calculation for timeout_ns and timeout_clk is zero
as well. So what we actually want to limit here is either SDHC
case or unreasonable timeout reported by the cards. In principle
we should at least be able to remove the bogus check for the
mmc_card_blockaddr.
Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
---
Changes in v2:
- rephrase the changelog and only remove mmc_card_blockaddr.
drivers/mmc/core/core.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 6177eb0..edc2e75 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -761,15 +761,11 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card)
limit_us = 100000;
/*
- * SDHC cards always use these fixed values.
+ * Assign limit value if invalid. Note that for the SDHC case,
+ * we set taac and nasc to zero when parsing CSD, so it's safe
+ * to fall through here.
*/
- if (timeout_us > limit_us || mmc_card_blockaddr(card)) {
- data->timeout_ns = limit_us * 1000;
- data->timeout_clks = 0;
- }
-
- /* assign limit value if invalid */
- if (timeout_us == 0)
+ if (timeout_us == 0 || timeout_us > limit_us)
data->timeout_ns = limit_us * 1000;
Shouldn't we still be ensuring 'data->timeout_clks = 0' for the 'timeout_us
limit_us' case
I have a question that why we expose data->timeout_clks for host
drivers?
I quick look at how the host drivers use it and find it almost does
the same thing as the core layer if card->host->ios.clock is present.
So shouldn't we *always* set data->timeout_clks to zero and fold the
extra cycle(actually it's NSAC) into data->timeout_ns so that the host
drivers only need to care about data->timeout_clks?
}
--
To unsubscribe from this list: send the line "unsubscribe linux-mmc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
