Hi Jaehoon,
On 2016/8/31 18:48, Jaehoon Chung wrote:
On 08/31/2016 04:13 PM, Shawn Lin wrote:
On 2016/8/31 13:51, Jaehoon Chung wrote:
HS400 mode doesn't need to do execute_tuning, because it's already
tuned in HS200 mode. And Tuning command is optional for UHS50 mode.
In future, the general execute_tuning sequence can be included in this
function.
Maybe this isn't what we want for mmc.
I see both of sd and sdio call mmc_execute_tuning by checking
the ios.timing, and explicitly we need to do tuning for
MMC_TIMING_UHS_SDR50 as the mmc core asks we to do that.
Moreover, why mmc didn't do something like:
if (card->host->ios.timing == MMC_TIMING_XXXXX || ....)
mmc_execute_tuning()
So we don't need every host driver to add these check and I do
see some host drivers check these timing for their execute_tuning
callback..
What is your opinion? :)
Yep, your comment makes sense..So i'm checking SD specification.
I think it needs to know which UHS card is..(UHS50 or UHS104)..
But current kernel can't distinguish these..
According to spec, we can distinguish UHS50 and UHS104 with TRAN_SPEED field.
"UHS50 Card set TRANS_SPEED to 0Bh (100Mbit/sec), for both SDR50 and DDR50 modes.
UHS104 Card set TRAN_SPEED to 2Bh (200Mbit/sec)"
I'm not sure it's helpful to me...but i will consider more...
Ah, are we on the same page? :)
I have some questions below.
Thanks you for comment. :)
Best Regards,
Jaehoon Chung
Signed-off-by: Jaehoon Chung <jh80.chung@xxxxxxxxxxx>
---
drivers/mmc/host/dw_mmc.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 22dacae..6571924 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1568,10 +1568,25 @@ static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode)
struct dw_mci_slot *slot = mmc_priv(mmc);
struct dw_mci *host = slot->host;
const struct dw_mci_drv_data *drv_data = host->drv_data;
- int err = -EINVAL;
+ int err = 0;
+
+ switch (host->timing) {
+ case MMC_TIMING_MMC_HS400:
+ err = -EINVAL;
What makes you think the code could be there? :)
By looking the code, it's impossible, no?
+ goto out;
+ case MMC_TIMING_MMC_HS200:
+ case MMC_TIMING_UHS_SDR104:
+ case MMC_TIMING_UHS_DDR50:
+ break;
+ case MMC_TIMING_UHS_SDR50:
+ /* Fall through */
dw_mmc even doesn't try to do tuning for SDR50?
+ default:
+ goto out;
+ }
That confused me more or less. What makes us gain confidence
that we could return 0 even if no any tuning process was done
before using UHS-I.
if (drv_data && drv_data->execute_tuning)
err = drv_data->execute_tuning(slot, opcode);
+out:
return err;
}
--
Best Regards
Shawn Lin
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