Re: [RFC V6 2/2] firmware: arm_scmi: Add quirk to bypass SCP fw bug

[Dan Carpenter <dan.carpenter@linaro.org>]

On Wed, Feb 26, 2025 at 08:13:38AM +0530, Sibi Sankar wrote:
> The addition of per message-id fastchannel support check exposed
> a SCP firmware bug which leads to a device crash on X1E platforms.

You're fixing a bug that is introduced in patch 1.  That's not allowed.
These need to be squashed into one patch.  I means the patch will be
slightly long and the commit message will be slightly long but I
feel like it's manageable.

> The X1E firmware supports fastchannel on LEVEL_GET but fails to
> have this set in the protocol message attributes and the fallback
> to regular messaging leads to a device crash since that implementation
> has a bug for all the X1E devices in the wild. Fix this by introducing
> a quirk that selectively skips the per message-id fastchannel check only
> for the LEVEL_GET message on X1E platforms.
> 
> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
> ---
>  drivers/firmware/arm_scmi/driver.c    |  5 +++--
>  drivers/firmware/arm_scmi/perf.c      | 30 +++++++++++++++++++++------
>  drivers/firmware/arm_scmi/powercap.c  |  8 +++----
>  drivers/firmware/arm_scmi/protocols.h |  2 +-
>  4 files changed, 32 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index 9313b9020fc1..b182fa8e8ccb 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -1903,7 +1903,8 @@ static void
>  scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
>  			     u8 describe_id, u32 message_id, u32 valid_size,
>  			     u32 domain, void __iomem **p_addr,
> -			     struct scmi_fc_db_info **p_db, u32 *rate_limit)
> +			     struct scmi_fc_db_info **p_db, u32 *rate_limit,
> +			     bool skip_check)
>  {
>  	int ret;
>  	u32 flags;
> @@ -1919,7 +1920,7 @@ scmi_common_fastchannel_init(const struct scmi_protocol_handle *ph,
>  
>  	/* Check if the MSG_ID supports fastchannel */
>  	ret = scmi_protocol_msg_check(ph, message_id, &attributes);
> -	if (!ret && !MSG_SUPPORTS_FASTCHANNEL(attributes))
> +	if (!ret && !MSG_SUPPORTS_FASTCHANNEL(attributes) && !skip_check)
>  		return;

This is explained well in the commit message but the comment here needs
to be better.  Also if scmi_protocol_msg_check() fails then we should
return.  Let's rename the variable to "force_fastchannel".

	ret = scmi_protocol_msg_check(ph, message_id, &attributes);
	if (ret)
		return;

	/*
	 * Check if the MSG_ID supports fastchannel.  The force_fastchannel
	 * quirk is necessary to work around a firmware bug.  We can probably
	 * remove that quirk in 2030.
	 */
	if (!force_fastchannel && !MSG_SUPPORTS_FASTCHANNEL(attributes))
		return;


>  
>  	if (!p_addr) {
> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
> index c7e5a34b254b..5b4559d0b054 100644
> --- a/drivers/firmware/arm_scmi/perf.c
> +++ b/drivers/firmware/arm_scmi/perf.c
> @@ -48,6 +48,10 @@ enum {
>  	PERF_FC_MAX,
>  };
>  
> +enum {
> +	PERF_QUIRK_SKIP_FASTCHANNEL_LEVEL_GET,
> +};

Let's keep the FORCE_FASTCHANNEL naming.  Normally we would do this like:

#define PERF_QUIRK_FORCE_FASTCHANNEL BIT(0)

> +
>  struct scmi_opp {
>  	u32 perf;
>  	u32 power;
> @@ -183,6 +187,7 @@ struct scmi_perf_info {
>  	enum scmi_power_scale power_scale;
>  	u64 stats_addr;
>  	u32 stats_size;
> +	u32 quirks;
>  	bool notify_lvl_cmd;
>  	bool notify_lim_cmd;
>  	struct perf_dom_info *dom_info;
> @@ -838,9 +843,10 @@ static int scmi_perf_level_limits_notify(const struct scmi_protocol_handle *ph,
>  }
>  
>  static void scmi_perf_domain_init_fc(const struct scmi_protocol_handle *ph,
> -				     struct perf_dom_info *dom)
> +				     struct perf_dom_info *dom, u32 quirks)
>  {
>  	struct scmi_fc_info *fc;
> +	bool quirk_level_get = !!(quirks & BIT(PERF_QUIRK_SKIP_FASTCHANNEL_LEVEL_GET));

	bool force_fastchannel = !!(quirks & PERF_QUIRK_FORCE_FASTCHANNEL);

>  
>  	fc = devm_kcalloc(ph->dev, PERF_FC_MAX, sizeof(*fc), GFP_KERNEL);
>  	if (!fc)

regards,
dan carpenter