Re: [PATCH v2 1/7] mmc: sdhci_am654: Add tuning algorithm for delay chain
From: Judith Mendez
Date: Tue Feb 20 2024 - 15:10:33 EST
Hi Adrian,
On 2/16/24 11:09 AM, Adrian Hunter wrote:
On 7/02/24 03:15, Judith Mendez wrote:
Currently the sdhci_am654 driver only supports one tuning
algorithm which should be used only when DLL is enabled. The
ITAPDLY is selected from the largest passing window and the
buffer is viewed as a circular buffer.
The new algorithm should be used when the delay chain
is enabled. The ITAPDLY is selected from the largest passing
window and the buffer is not viewed as a circular buffer.
This implementation is based off of the following paper: [1].
Also add support for multiple failing windows.
[1] https://www.ti.com/lit/an/spract9/spract9.pdf
Fixes: 13ebeae68ac9 ("mmc: sdhci_am654: Add support for software tuning")
Signed-off-by: Judith Mendez <jm@xxxxxx>
---
Changelog:
v1->v2:
- Remove unnecessary indentations and if/else in
sdhci_am654_calculate_itap()
- Optimize sdhci_am654_calculate_itap()
---
drivers/mmc/host/sdhci_am654.c | 111 +++++++++++++++++++++++++++------
1 file changed, 91 insertions(+), 20 deletions(-)
diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
index d659c59422e1..2c66a965c225 100644
--- a/drivers/mmc/host/sdhci_am654.c
+++ b/drivers/mmc/host/sdhci_am654.c
@@ -149,10 +149,17 @@ struct sdhci_am654_data {
int strb_sel;
u32 flags;
u32 quirks;
+ bool dll_enable;
#define SDHCI_AM654_QUIRK_FORCE_CDTEST BIT(0)
};
+struct window {
+ u8 start;
+ u8 end;
+ u8 length;
+};
+
struct sdhci_am654_driver_data {
const struct sdhci_pltfm_data *pdata;
u32 flags;
@@ -290,10 +297,13 @@ static void sdhci_am654_set_clock(struct sdhci_host *host, unsigned int clock)
regmap_update_bits(sdhci_am654->base, PHY_CTRL4, mask, val);
- if (timing > MMC_TIMING_UHS_SDR25 && clock >= CLOCK_TOO_SLOW_HZ)
+ if (timing > MMC_TIMING_UHS_SDR25 && clock >= CLOCK_TOO_SLOW_HZ) {
sdhci_am654_setup_dll(host, clock);
- else
+ sdhci_am654->dll_enable = true;
+ } else {
sdhci_am654_setup_delay_chain(sdhci_am654, timing);
+ sdhci_am654->dll_enable = false;
+ }
regmap_update_bits(sdhci_am654->base, PHY_CTRL5, CLKBUFSEL_MASK,
sdhci_am654->clkbuf_sel);
@@ -408,39 +418,100 @@ static u32 sdhci_am654_cqhci_irq(struct sdhci_host *host, u32 intmask)
return 0;
}
-#define ITAP_MAX 32
+#define ITAPDLY_LENGTH 32
+#define ITAPDLY_LAST_INDEX 31
Presumably ITAPDLY_LAST_INDEX == ITAPDLY_LENGTH - 1, so perhaps:
#define ITAPDLY_LAST_INDEX (ITAPDLY_LENGTH - 1)
Blank line here perhaps.
This does seem easier to read, will add for v3.
+static u32 sdhci_am654_calculate_itap(struct sdhci_host *host, struct window
+ *fail_window, u8 num_fails, bool circular_buffer)
+{
+ struct device *dev = mmc_dev(host->mmc);
+ struct window pass_window = {0, 0, 0};
+ u8 first_fail_start = 0, last_fail_end = 0;
+ int prev_fail_end = -1;
+ u8 itap = 0, start_fail = 0, end_fail = 0, pass_length = 0;
+ u8 i;
Some prefer ordering of variable declarations at the beginning of a
function to be "reverse fir tree" order, in other words, longer lines
first, e.g.
u8 itap = 0, start_fail = 0, end_fail = 0, pass_length = 0;
u8 first_fail_start = 0, last_fail_end = 0;
struct device *dev = mmc_dev(host->mmc);
struct window pass_window = {0, 0, 0};
int prev_fail_end = -1;
u8 i;
Understood, will add for v3.
+
+ if (!num_fails)
+ return ITAPDLY_LAST_INDEX >> 1;
+
+ if (fail_window->length == ITAPDLY_LENGTH) {
+ dev_err(dev, "No passing ITAPDLY, return 0\n");
+ return 0;
+ }
+
+ first_fail_start = fail_window->start;
+ last_fail_end = fail_window[num_fails - 1].end;
+
+ for (i = 0; i < num_fails; i++) {
+ start_fail = fail_window[i].start;
+ end_fail = fail_window[i].end;
+ pass_length = start_fail - (prev_fail_end + 1);
+
+ if (pass_length > pass_window.length) {
+ pass_window.start = prev_fail_end + 1;
+ pass_window.length = pass_length;
+ }
+ prev_fail_end = end_fail;
+ }
+
+ if (!circular_buffer)
+ pass_length = ITAPDLY_LAST_INDEX - last_fail_end;
+ else
+ pass_length = ITAPDLY_LAST_INDEX - last_fail_end + first_fail_start;
+
+ if (pass_length > pass_window.length) {
+ pass_window.start = last_fail_end + 1;
+ pass_window.length = pass_length;
+ }
+
+ if (!circular_buffer)
+ itap = pass_window.start + (pass_window.length >> 1);
+ else
+ itap = (pass_window.start + (pass_window.length >> 1)) % ITAPDLY_LENGTH;
+
+ return (itap < 0 || itap > ITAPDLY_LAST_INDEX ? 0 : itap);
Parentheses are not needed where they are but putting
them around the condition would make it more readable e.g.
return (itap < 0 || itap > ITAPDLY_LAST_INDEX) ? 0 : itap;
However (itap < 0) is not possible because itap is an unsigned type
and if (itap > ITAPDLY_LAST_INDEX) then maybe it would be better
to return ITAPDLY_LAST_INDEX
You are right about itap < 0, thanks will fix.
About itap > ITAPDLY_LAST_INDEX, this is an error. Why
return ITAPDLY_LAST_INDEX instead of 0?
+}
+
static int sdhci_am654_platform_execute_tuning(struct sdhci_host *host,
u32 opcode)
{
struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
struct sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);
- int cur_val, prev_val = 1, fail_len = 0, pass_window = 0, pass_len;
- u32 itap;
+ struct window fail_window[ITAPDLY_LENGTH];
+ u8 prev_pass = 1;
+ u8 fail_index = 0;
+ u8 curr_pass, itap;
Perhaps reverse fir tree
Will add fix here as well.
+
+ memset(fail_window, 0, sizeof(fail_window[0]) * ITAPDLY_LENGTH);
This can be:
memset(fail_window, 0, sizeof(fail_window));
This does look simpler, will add for v3.
/* Enable ITAPDLY */
regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPDLYENA_MASK,
1 << ITAPDLYENA_SHIFT);
- for (itap = 0; itap < ITAP_MAX; itap++) {
+ for (itap = 0; itap < ITAPDLY_LENGTH; itap++) {
sdhci_am654_write_itapdly(sdhci_am654, itap);
- cur_val = !mmc_send_tuning(host->mmc, opcode, NULL);
- if (cur_val && !prev_val)
- pass_window = itap;
+ curr_pass = !mmc_send_tuning(host->mmc, opcode, NULL);
- if (!cur_val)
- fail_len++;
+ if (!curr_pass && prev_pass)
+ fail_window[fail_index].start = itap;
- prev_val = cur_val;
+ if (!curr_pass) {
+ fail_window[fail_index].end = itap;
+ fail_window[fail_index].length++;
+ }
+
+ if (curr_pass && !prev_pass)
+ fail_index++;
+
+ prev_pass = curr_pass;
}
- /*
- * Having determined the length of the failing window and start of
- * the passing window calculate the length of the passing window and
- * set the final value halfway through it considering the range as a
- * circular buffer
- */
- pass_len = ITAP_MAX - fail_len;
- itap = (pass_window + (pass_len >> 1)) % ITAP_MAX;
+
+ if (fail_window[fail_index].length != 0)
+ fail_index++;
+
+ itap = sdhci_am654_calculate_itap(host, fail_window, fail_index,
+ (sdhci_am654->dll_enable));
Parentheses around sdhci_am654->dll_enable are not needed.
Agree, I can remove for v3.
+
sdhci_am654_write_itapdly(sdhci_am654, itap);
return 0;
My apologies for the late reply and thanks for reviewing.
~ Judith