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Message-ID: <CANLsYkw59pvjc-Q6oVX+wB40nrzjuZ8V0hgdKT=sK=sH+HY-gw@mail.gmail.com>
Date: Mon, 25 Apr 2016 08:55:20 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Suzuki K Poulose <Suzuki.Poulose@....com>
Cc: "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 14/18] coresight: tmc: keep track of memory width
On 25 April 2016 at 08:41, Suzuki K Poulose <Suzuki.Poulose@....com> wrote:
> On 22/04/16 18:14, Mathieu Poirier wrote:
>>
>> Accessing the HW configuration register each time the memory
>> width is needed simply doesn't make sense. It is much more
>> efficient to read the value once and keep a reference for
>> later use.
>>
>> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
>> ---
>> drivers/hwtracing/coresight/coresight-tmc-etf.c | 14 +---------
>> drivers/hwtracing/coresight/coresight-tmc.c | 34
>> +++++++++++++++++++++++++
>> drivers/hwtracing/coresight/coresight-tmc.h | 10 +++++---
>> 3 files changed, 41 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> index cc88c15ba45c..981c5ca75e36 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>> @@ -41,25 +41,13 @@ void tmc_etb_enable_hw(struct tmc_drvdata *drvdata)
>>
>> static void tmc_etb_dump_hw(struct tmc_drvdata *drvdata)
>> {
>> - enum tmc_mem_intf_width memwidth;
>> - u8 memwords;
>> char *bufp;
>> u32 read_data;
>> int i;
>>
>> - memwidth = BMVAL(readl_relaxed(drvdata->base + CORESIGHT_DEVID),
>> 8, 10);
>> - if (memwidth == TMC_MEM_INTF_WIDTH_32BITS)
>> - memwords = 1;
>> - else if (memwidth == TMC_MEM_INTF_WIDTH_64BITS)
>> - memwords = 2;
>> - else if (memwidth == TMC_MEM_INTF_WIDTH_128BITS)
>> - memwords = 4;
>> - else
>> - memwords = 8;
>> -
>> bufp = drvdata->buf;
>> while (1) {
>> - for (i = 0; i < memwords; i++) {
>> + for (i = 0; i < drvdata->memwidth; i++) {
>> read_data = readl_relaxed(drvdata->base +
>> TMC_RRD);
>> if (read_data == 0xFFFFFFFF)
>> return;
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.c
>> b/drivers/hwtracing/coresight/coresight-tmc.c
>> index 55806352b1f1..cb030a09659d 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.c
>> @@ -193,6 +193,39 @@ static const struct file_operations tmc_fops = {
>> .llseek = no_llseek,
>> };
>>
>> +static enum tmc_mem_intf_width tmc_get_memwidth(u32 devid)
>> +{
>> + enum tmc_mem_intf_width memwidth;
>> +
>> + /*
>> + * Excerpt from the TRM:
>> + *
>> + * DEVID::MEMWIDTH[10:8]
>> + * 0x2 Memory interface databus is 32 bits wide.
>> + * 0x3 Memory interface databus is 64 bits wide.
>> + * 0x4 Memory interface databus is 128 bits wide.
>> + * 0x5 Memory interface databus is 256 bits wide.
>> + */
>> + switch (BMVAL(devid, 8, 10)) {
>> + case 0x2:
>> + memwidth = TMC_MEM_INTF_WIDTH_32BITS;
>> + break;
>> + case 0x3:
>> + memwidth = TMC_MEM_INTF_WIDTH_64BITS;
>> + break;
>> + case 0x4:
>> + memwidth = TMC_MEM_INTF_WIDTH_128BITS;
>> + break;
>> + case 0x5:
>> + memwidth = TMC_MEM_INTF_WIDTH_256BITS;
>> + break;
>> + default:
>> + memwidth = 0;
>> + }
>> +
>> + return memwidth;
>> +}
>> +
>> #define coresight_tmc_simple_func(name, offset) \
>> coresight_simple_func(struct tmc_drvdata, name, offset)
>>
>> @@ -306,6 +339,7 @@ static int tmc_probe(struct amba_device *adev, const
>> struct amba_id *id)
>>
>> devid = readl_relaxed(drvdata->base + CORESIGHT_DEVID);
>> drvdata->config_type = BMVAL(devid, 6, 7);
>> + drvdata->memwidth = tmc_get_memwidth(devid);
>>
>> if (drvdata->config_type == TMC_CONFIG_TYPE_ETR) {
>> if (np)
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h
>> b/drivers/hwtracing/coresight/coresight-tmc.h
>> index 9b4c215d2b6b..12a097f3d06c 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.h
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
>> @@ -81,10 +81,10 @@ enum tmc_mode {
>> };
>>
>> enum tmc_mem_intf_width {
>> - TMC_MEM_INTF_WIDTH_32BITS = 0x2,
>> - TMC_MEM_INTF_WIDTH_64BITS = 0x3,
>> - TMC_MEM_INTF_WIDTH_128BITS = 0x4,
>> - TMC_MEM_INTF_WIDTH_256BITS = 0x5,
>> + TMC_MEM_INTF_WIDTH_32BITS = 1,
>> + TMC_MEM_INTF_WIDTH_64BITS = 2,
>> + TMC_MEM_INTF_WIDTH_128BITS = 4,
>> + TMC_MEM_INTF_WIDTH_256BITS = 8,
>> };
>
>
> I think this would cause confusion for the reader. It would be good to
> leave the definitions above as before and tmc_get_memwidth() doing:
>
> i.e,
> case TMC_MEM_INTF_WIDTH_32BITS:
> memwidth = 1;
> break;
>
> But we still store the memwidth in bytes.
If we proceed this way we have to do a case statement on hard coded
values (or introduce a new enumeration) in tmc_update_etf_buffer(). In
my opinion the current solution scales better.
Mathieu
>
> Suzuki
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