Re: [PATCH v5 3/7] drm/msm: adreno: dynamically generate GMU bw table

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 11.12.2024 9:29 AM, Neil Armstrong wrote:
> The Adreno GPU Management Unit (GMU) can also scale the ddr
> bandwidth along the frequency and power domain level, but for
> now we statically fill the bw_table with values from the
> downstream driver.
> 
> Only the first entry is used, which is a disable vote, so we
> currently rely on scaling via the linux interconnect paths.
> 
> Let's dynamically generate the bw_table with the vote values
> previously calculated from the OPPs.
> 
> Those entries will then be used by the GMU when passing the
> appropriate bandwidth level while voting for a gpu frequency.
> 
> Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 48 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 47 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> index cb8844ed46b29c4569d05eb7a24f7b27e173190f..995526620d678cd05020315f771213e4a6943bec 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> @@ -6,6 +6,7 @@
>  #include <linux/list.h>
>  
>  #include <soc/qcom/cmd-db.h>
> +#include <soc/qcom/tcs.h>
>  
>  #include "a6xx_gmu.h"
>  #include "a6xx_gmu.xml.h"
> @@ -259,6 +260,48 @@ static int a6xx_hfi_send_perf_table(struct a6xx_gmu *gmu)
>  		NULL, 0);
>  }
>  
> +static void a6xx_generate_bw_table(const struct a6xx_info *info, struct a6xx_gmu *gmu,
> +				   struct a6xx_hfi_msg_bw_table *msg)
> +{
> +	unsigned int i, j;
> +
> +	for (i = 0; i < GMU_MAX_BCMS; i++) {
> +		if (!info->bcms[i].name)
> +			break;
> +		msg->ddr_cmds_addrs[i] = cmd_db_read_addr(info->bcms[i].name);
> +	}
> +	msg->ddr_cmds_num = i;
> +
> +	for (i = 0; i < gmu->nr_gpu_bws; ++i)
> +		for (j = 0; j < msg->ddr_cmds_num; j++)
> +			msg->ddr_cmds_data[i][j] = gmu->gpu_ib_votes[i][j];
> +	msg->bw_level_num = gmu->nr_gpu_bws;
> +
> +	/* Compute the wait bitmask with each BCM having the commit bit */
> +	msg->ddr_wait_bitmask = 0;
> +	for (j = 0; j < msg->ddr_cmds_num; j++)
> +		if (msg->ddr_cmds_data[0][j] & BCM_TCS_CMD_COMMIT_MASK)
> +			msg->ddr_wait_bitmask |= BIT(j);
> +
> +	/*
> +	 * These are the CX (CNOC) votes - these are used by the GMU
> +	 * The 'CN0' BCM is used on all targets, and votes are basically
> +	 * 'off' and 'on' states with first bit to enable the path.
> +	 */
> +

/* The CNoC BCM only needs a simple off/on vote pair on all platforms */

> +	msg->cnoc_cmds_addrs[0] = cmd_db_read_addr("CN0");
> +	msg->cnoc_cmds_num = 1;
> +
> +	msg->cnoc_cmds_data[0][0] = BCM_TCS_CMD(true, false, 0, 0);
> +	msg->cnoc_cmds_data[1][0] = BCM_TCS_CMD(true, true, 0, BIT(0));

While it evaluates to the same, I think this is logically 1 (as in, one
unit of bus rate). The question of which bit that corresponds to is
handled by the macro.

Also, a7xx sets values in both x and y parts here, while a6xx only does
so in the y part.

> +
> +	/* Compute the wait bitmask with each BCM having the commit bit */
> +	msg->cnoc_wait_bitmask = 0;
> +	for (j = 0; j < msg->cnoc_cmds_num; j++)
> +		if (msg->cnoc_cmds_data[0][j] & BCM_TCS_CMD_COMMIT_MASK)
> +			msg->cnoc_wait_bitmask |= BIT(j);

This is a very fancy way to say msg->cnoc_wait_bitmask = BIT(0)

Konrad