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Date: Wed, 31 Jan 2024 14:27:27 -0600
From: Judith Mendez <jm@...com>
To: Vignesh Raghavendra <vigneshr@...com>,
Ulf Hansson
<ulf.hansson@...aro.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof
Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley
<conor+dt@...nel.org>
CC: Adrian Hunter <adrian.hunter@...el.com>, <linux-mmc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, Nishanth Menon <nm@...com>,
Andrew Davis
<afd@...com>, Udit Kumar <u-kumar1@...com>,
Roger Quadros
<rogerq@...nel.org>, <devicetree@...r.kernel.org>,
Randolph Sapp <rs@...com>
Subject: Re: [RFC PATCH 01/13] drivers: mmc: host: sdhci_am654: Add tuning
algorithm for delay chain
On 1/31/24 5:04 AM, Vignesh Raghavendra wrote:
> Hi Judith,
>
> On 31/01/24 06:07, 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
>>
>> Signed-off-by: Judith Mendez <jm@...com>
>> ---
>
>
> $subject prefix should be
>
> mmc: sdhci_am654:
>
> See git log --oneline drivers/mmc/host/sdhci_am654.c for precedence.
Thanks, will add in v1.
>
>> drivers/mmc/host/sdhci_am654.c | 128 +++++++++++++++++++++++++++------
>> 1 file changed, 108 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
>> index d659c59422e1..59d205511312 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 +418,117 @@ 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
>> +static u32 calculate_itap(struct sdhci_host *host, struct window *fail_window,
>> + u8 num_fails, bool circular_buffer)
>
>
> s/calculate_itap/sdhci_am654_calculate_itap/ to keep function naming
> consistent within the file
Will add.
>
>> +{
>> + struct device *dev = mmc_dev(host->mmc);
>> + struct window pass_window, first_fail, last_fail;
>> + u8 itap = 0, start_fail = 0, end_fail = 0, pass_length = 0;
>> + int prev_end_fail = -1;
>> +
>> + memset(&pass_window, 0, sizeof(pass_window));
>> + memset(&first_fail, 0, sizeof(first_fail));
>> + memset(&last_fail, 0, sizeof(last_fail));
>> +
>> + if (!num_fails) {
>> + return ITAPDLY_LAST_INDEX >> 1;
>> + } else if (fail_window->length == ITAPDLY_LENGTH) {
>> + dev_warn(dev, "No passing ITAPDLY, return 0\n");
>
> Drop return 0 in dev_warn()
Good idea, will update itap value here then.
>
>> + return 0;
>
> Should this be an error?
It is an error, but I thought it was a good idea to return 0 in case all
ITAPDLY values fail and report this via dev_warn or dev_error. For now I
can use dev_error.
>
>> + } else {
>> + for (int i = 0; i < num_fails; i++) {
>
>
> please avoid inline declaration to align with rest of the file.
Will do.
>
>> + start_fail = fail_window[i].start;
>> + end_fail = fail_window[i].end;
>> +
>> + if (i == 0) {
>> + first_fail.start = start_fail;
>> + first_fail.end = end_fail;
>> + first_fail.length = fail_window[0].length;
>> + }
>> +
>> + if (i == num_fails - 1) {
>> + last_fail.start = start_fail;
>> + last_fail.end = end_fail;
>> + last_fail.length = fail_window[i].length;
>> + }
>> +
>> + pass_length = start_fail - (prev_end_fail + 1);
>> + if (pass_length > pass_window.length) {
>> + pass_window.start = prev_end_fail + 1;
>> + pass_window.length = pass_length;
>> + }
>> + prev_end_fail = end_fail;
>> + }
>> +
>> + if (!circular_buffer) {
>> + if (ITAPDLY_LAST_INDEX - end_fail > pass_window.length) {
>> + pass_window.start = end_fail + 1;
>> + pass_window.length = ITAPDLY_LAST_INDEX - end_fail;
>> + }
>> + } else {
>> + pass_length = ITAPDLY_LAST_INDEX - end_fail + 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;
>> +
>> + if (itap < 0 || itap > ITAPDLY_LAST_INDEX)
>> + itap = 0;
>> +
>> + return itap;
>> +}
>> +
>> 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, i;
>> +
>> + for (i = 0; i < ITAPDLY_LENGTH; i++)
>> + memset(&fail_window[i], 0, sizeof(fail_window[0]));
>
> Don't need for() loop, just memset entire array at once. Something like:
>
> memset(fail_window, 0, sizeof(fail_window[0]) * ITAPDLY_LENGTH);
Great, will add this, thanks.
>
>>
>> /* 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++;
>
> These is some tab vs space mangling here.
I will fix this. (:
>
>> +
>> + itap = calculate_itap(host, &fail_window[0], fail_index,
>> + (sdhci_am654->dll_enable ? true : false));
>> +
>> sdhci_am654_write_itapdly(sdhci_am654, itap);
>>
>> return 0;
>
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