Re: [PATCH v3 7/9] mmc: sdhci-msm: Implement set_clock callback for sdhci-msm

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Hi Adrian,


On 8/22/2016 2:59 PM, Adrian Hunter wrote:
On 22/08/16 12:07, Ritesh Harjani wrote:
Hi Adrian,


On 8/22/2016 11:50 AM, Adrian Hunter wrote:
On 19/08/16 16:31, Ritesh Harjani wrote:
Hi,


On 8/19/2016 6:34 PM, Adrian Hunter wrote:
On 19/08/16 07:36, Ritesh Harjani wrote:
sdhci-msm controller may have different clk-rates for each
bus speed mode. Thus implement set_clock callback for
sdhci-msm driver.

Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
Signed-off-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxxx>
---
 drivers/mmc/host/sdhci-msm.c | 103
++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 102 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index 7c032c3..c0ad9c2 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -89,6 +89,7 @@ struct sdhci_msm_host {
     struct mmc_host *mmc;
     bool use_14lpp_dll_reset;
     struct sdhci_msm_pltfm_data *pdata;
+    u32 clk_rate;
 };

 /* Platform specific tuning */
@@ -582,6 +583,106 @@ static unsigned int sdhci_msm_get_min_clock(struct
sdhci_host *host)
     return msm_host->pdata->clk_table[0];
 }

+static unsigned int sdhci_msm_get_msm_clk_rate(struct sdhci_host *host,
+                    u32 req_clk)
+{
+    struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+    struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+    int count = msm_host->pdata->clk_table_sz;
+    unsigned int sel_clk = -1;
+    int cnt;
+
+    if (req_clk < sdhci_msm_get_min_clock(host)) {
+        sel_clk = sdhci_msm_get_min_clock(host);
+        return sel_clk;
+    }
+
+    for (cnt = 0; cnt < count; cnt++) {
+        if (msm_host->pdata->clk_table[cnt] > req_clk) {
+            break;
+        } else if (msm_host->pdata->clk_table[cnt] == req_clk) {
+            sel_clk = msm_host->pdata->clk_table[cnt];
+            break;
+        } else {
+            sel_clk = msm_host->pdata->clk_table[cnt];
+        }
+    }
'else' is not needed after 'break' but can't this be simpler e.g.

static unsigned int sdhci_msm_get_msm_clk_rate(struct sdhci_msm_host
*msm_host, u32 req_clk)
{
    int count = msm_host->pdata->clk_table_sz;
    unsigned int sel_clk = -1;

    while (count--) {
        sel_clk = msm_host->pdata->clk_table[count];
        if (req_clk >= sel_clk)
            return sel_clk;
    }

    return sel_clk;
}
Ok, sure I will check and get back on this.



+    return sel_clk;
+}
Blank line needed
Ok done.

+/**
+ * __sdhci_msm_set_clock - sdhci_msm clock control.
+ *
+ * Description:
+ * Implement MSM version of sdhci_set_clock.
+ * This is required since MSM controller does not
+ * use internal divider and instead directly control
+ * the GCC clock as per HW recommendation.
+ **/
+void __sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
+{
+    u16 clk;
+    unsigned long timeout;
+
+    host->mmc->actual_clock = 0;
+
+    sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
+
+    if (clock == 0)
+        return;
Should set host->mmc->actual_clock to the actual rate somewhere.
Since MSM controller does not uses divider then there is no need of having
actual clock since it should be same as host->clock.
Ok, so sdhci_msm_get_msm_clk_rate() is not the actual clock rate?
So I was assuming we need host->mmc->actual_clock rate if host->clock is not
the actual rate.
Ok, so I will update actual_clock to host->clock itself.

pls, let me know if any concerns.
I am confused.  Isn't clk_get_rate(msm_host->clk) the actual clock rate?
Actually, msm controller have few quirks around clocks itself and
I was thinking of not using actual_clock to avoid adding any extra quirks for msm.
If you see if actual_clock is 0 and if 
SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK is set, timeout_clk take host->clock 
for timeout calculation.
That's one reason I did not want to update the host->actual_clock. 
(otherwise timeout calc will go wrong for DDR modes for msm, where clock 
from GCC is made double of host->clock and internally divided by 
controller on it's own. In this case actual_clock would be shown as 2x 
of host->clock).
Do you think that keeping actual_clock to 0 should be fine in this case?


I have not yet worked over timeout calculation patches yet, since it is of lower priority in my list. After few other areas (mostly HS400), I will take over clock timeout fixes to be up-streamed.
That's why I had kept it 0 intentionally. But I will add a comment
here then.

+
+    /*
+     * MSM controller do not use clock divider.
+     * Thus read SDHCI_CLOCK_CONTROL and only enable
+     * clock with no divider value programmed.
+     */
+    clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+
+    clk |= SDHCI_CLOCK_INT_EN;
+    sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
+
+    /* Wait max 20 ms */
+    timeout = 20;
+    while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
+        & SDHCI_CLOCK_INT_STABLE)) {
+        if (timeout == 0) {
+            pr_err("%s: Internal clock never stabilised.\n",
+                   mmc_hostname(host->mmc));
+            return;
+        }
+        timeout--;
+        mdelay(1);
+    }
+
+    clk |= SDHCI_CLOCK_CARD_EN;
+    sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
+}
+
+static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int
clock)
+{
+    struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+    struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+    u32 msm_clock = 0;
+    int rc = 0;
+
+    if (!clock)
+        goto out;
+
+    if (clock != msm_host->clk_rate) {
+        msm_clock = sdhci_msm_get_msm_clk_rate(host, clock);
+        rc = clk_set_rate(msm_host->clk, msm_clock);
+        if (rc) {
+            pr_err("%s: failed to set clock at rate %u, requested clock
rate %u\n",
+                mmc_hostname(host->mmc), msm_clock, clock);
+            goto out;
+        }
+        msm_host->clk_rate = clock;
+        pr_debug("%s: setting clock at rate %lu\n",
+            mmc_hostname(host->mmc), clk_get_rate(msm_host->clk));
+    }
+out:
+    __sdhci_msm_set_clock(host, clock);
+}
+
 static const struct of_device_id sdhci_msm_dt_match[] = {
     { .compatible = "qcom,sdhci-msm-v4" },
     {},
@@ -592,7 +693,7 @@ MODULE_DEVICE_TABLE(of, sdhci_msm_dt_match);
 static const struct sdhci_ops sdhci_msm_ops = {
     .platform_execute_tuning = sdhci_msm_execute_tuning,
     .reset = sdhci_reset,
-    .set_clock = sdhci_set_clock,
+    .set_clock = sdhci_msm_set_clock,
     .get_min_clock = sdhci_msm_get_min_clock,
     .get_max_clock = sdhci_msm_get_max_clock,
     .set_bus_width = sdhci_set_bus_width,

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