linux-kernel - use default speed of the eMMC

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Message-ID: <CA+pahgdKJThHSgCppP-roqF905hkopjv3Pj6Kc7GVaR5gS7oxg@mail.gmail.com>
Date:	Tue, 24 May 2016 18:05:04 +0900
From:	장민우 <huskey27@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: use default speed of the eMMC

Dear chrisball.

Hello, I'm Minwoo Jang.

I have a question about using default speed of the eMMC.

When default speed is used, mmc_select_bus_width() is never called.

So, eMMC can not be set 4 bit or 8 bit bus width, I think.

Please, give me your opinions on the following diff codes.

Thank you.

=====================================================

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 94b4462..3b1cc4d 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -952,6 +952,8 @@ static int mmc_select_bus_width(struct mmc_card *card)

                if (!err) {
                        err = bus_width;
+                       pr_warn("%s: switch to bus width %d\n",
+                               mmc_hostname(host), (1 << bus_width));
                        break;
                } else {
                        pr_warn("%s: switch to bus width %d failed\n",
@@ -1500,6 +1502,14 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
                        if (err)
                                goto err;
                }
+       } else {
+               /* Select the bus width for normal speed mode */
+               err = mmc_select_bus_width(card);
+               if (IS_ERR_VALUE(err)) {
+                       pr_warn("%s: Selecting bus width failed\n",
+                               mmc_hostname(card->host));
+                       goto err;
+               }
        }

Best regards,

MW Jang.