| Message ID | 1453511240-20792-2-git-send-email-pprakash@codeaurora.org (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
On Fri, Jan 22, 2016 at 7:07 PM, Prashanth Prakash <pprakash@codeaurora.org> wrote: > static void __iomem *pcc_comm_addr; > static u64 comm_base_addr; > static int pcc_subspace_idx = -1; > -static u16 pcc_cmd_delay; > static bool pcc_channel_acquired; > +static ktime_t deadline; > > /* > * Arbitrary Retries in case the remote processor is slow to respond > - * to PCC commands. > + * to PCC commands. Keeping it high enough to cover emulators where > + * the processors run painfully slow. > */ > #define NUM_RETRIES 500 > > +static int check_pcc_chan(void) > +{ > + int result = -EIO; > + struct acpi_pcct_shared_memory *generic_comm_base = > + (struct acpi_pcct_shared_memory *) pcc_comm_addr; You're typecasting away the __iomem, and you don't need a typecast for void pointers. This should be: struct acpi_pcct_shared_memory __iomem *generic_comm_base = pcc_comm_addr; > + ktime_t next_deadline = ktime_add(ktime_get(), deadline); > + int retries = 0; > + > + /* Retry in case the remote processor was too slow to catch up. */ > + while (!ktime_after(ktime_get(), next_deadline)) { > + if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { > + result = 0; > + break; > + } > + /* > + * Reducing the bus traffic in case this loop takes longer than > + * a few retries. > + */ > + udelay(3); > + retries++; You don't actually use 'retries' in this function, so just delete it. Besides, you should be using readl_poll_timeout, instead of this loop. It handles the udelay and the ktime for you. > + } > + > + return result; > +} > + > static int send_pcc_cmd(u16 cmd) > { > - int retries, result = -EIO; > - struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv; > + int ret = -EIO; Please be consistent in your return variable names. Sometimes you use 'result', sometimes 'ret'. Pick one (my preference is 'ret') and use it exclusively. > struct acpi_pcct_shared_memory *generic_comm_base = > (struct acpi_pcct_shared_memory *) pcc_comm_addr; You have the same problem with __iomem here. And don't forget to CC: me and Ashwin on all future versions of this patchset.
On 25 January 2016 at 12:19, Timur Tabi <timur@codeaurora.org> wrote: > On Fri, Jan 22, 2016 at 7:07 PM, Prashanth Prakash > <pprakash@codeaurora.org> wrote: >> static void __iomem *pcc_comm_addr; >> static u64 comm_base_addr; >> static int pcc_subspace_idx = -1; >> -static u16 pcc_cmd_delay; >> static bool pcc_channel_acquired; >> +static ktime_t deadline; >> >> /* >> * Arbitrary Retries in case the remote processor is slow to respond >> - * to PCC commands. >> + * to PCC commands. Keeping it high enough to cover emulators where >> + * the processors run painfully slow. >> */ >> #define NUM_RETRIES 500 >> >> +static int check_pcc_chan(void) >> +{ >> + int result = -EIO; >> + struct acpi_pcct_shared_memory *generic_comm_base = >> + (struct acpi_pcct_shared_memory *) pcc_comm_addr; > > You're typecasting away the __iomem, and you don't need a typecast for > void pointers. This should be: > > struct acpi_pcct_shared_memory __iomem *generic_comm_base = pcc_comm_addr; > >> + ktime_t next_deadline = ktime_add(ktime_get(), deadline); >> + int retries = 0; >> + >> + /* Retry in case the remote processor was too slow to catch up. */ >> + while (!ktime_after(ktime_get(), next_deadline)) { >> + if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { >> + result = 0; >> + break; >> + } >> + /* >> + * Reducing the bus traffic in case this loop takes longer than >> + * a few retries. >> + */ >> + udelay(3); >> + retries++; > > You don't actually use 'retries' in this function, so just delete it. > Besides, you should be using readl_poll_timeout, instead of this loop. > It handles the udelay and the ktime for you. > >> + } >> + >> + return result; >> +} >> + >> static int send_pcc_cmd(u16 cmd) >> { >> - int retries, result = -EIO; >> - struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv; >> + int ret = -EIO; > > Please be consistent in your return variable names. Sometimes you use > 'result', sometimes 'ret'. Pick one (my preference is 'ret') and use > it exclusively. > >> struct acpi_pcct_shared_memory *generic_comm_base = >> (struct acpi_pcct_shared_memory *) pcc_comm_addr; > > You have the same problem with __iomem here. > > And don't forget to CC: me and Ashwin on all future versions of this patchset. Prashanth has been doing the right thing all along. I was CC'd on all his patchwork, but you changed it (and removed me) while replying. Unless Rafael thinks otherwise, I see no major issues in V2, so there is no need for a respin. Ashwin -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Ashwin Chaugule wrote: > Prashanth has been doing the right thing all along. I was CC'd on all > his patchwork, but you changed it (and removed me) while replying. I did not remove your CC:. I can't explain it, but the patch "[Linaro-acpi] [PATCH V2 1/4] ACPI / CPPC: Optimize PCC Read Write operations" in my inbox does not list you on the CC: This is what the header says: From: Prashanth Prakash <pprakash@codeaurora.org> To: rjw@rjwysocki.net Date: Fri, 22 Jan 2016 18:07:17 -0700 Message-Id: <1453511240-20792-2-git-send-email-pprakash@codeaurora.org> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1453511240-20792-1-git-send-email-pprakash@codeaurora.org> References: <1453511240-20792-1-git-send-email-pprakash@codeaurora.org> X-Virus-Scanned: ClamAV using ClamSMTP Cc: linux-acpi@vger.kernel.org, Prashanth Prakash <pprakash@codeaurora.org>, linaro-acpi@lists.linaro.org Subject: [Linaro-acpi] [PATCH V2 1/4] ACPI / CPPC: Optimize PCC Read Write operations X-BeenThere: linaro-acpi@lists.linaro.org When I look at the spinics.net archive, I see you are on it: http://www.spinics.net/lists/linux-acpi/msg63274.html I do not understand why my email does not have your CC: on it. > Unless Rafael thinks otherwise, I see no major issues in V2, so there > is no need for a respin. I think stripping away the __iomem is wrong. The whole point behind the 'sparse' tool is to catch invalid accesses to I/O memory. When you typecast it away, then prevent sparse from catching those problem. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Ashwin/Timur, >> Unless Rafael thinks otherwise, I see no major issues in V2, so there >> is no need for a respin. > > I think stripping away the __iomem is wrong. The whole point behind the 'sparse' tool is to catch invalid accesses to I/O memory. When you typecast it away, then prevent sparse from catching those problem. Thanks for your inputs. I will wait for few more days for feedback from Rafael and others before another respin with the suggested changes. Thanks, Prashanth -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Prashanth and Ashwin, On Sat, Jan 23, 2016 at 1:07 AM, Prashanth Prakash <pprakash@codeaurora.org> wrote: > From: Ashwin Chaugule <ashwin.chaugule@linaro.org> > > Previously the send_pcc_cmd() code checked if the > PCC operation had completed before returning from > the function. This check was performed regardless > of the PCC op type (i.e. Read/Write). Knowing > the type of cmd can be used to optimize the check > and avoid needless waiting. e.g. with Write ops, > the actual Writing is done before calling send_pcc_cmd(). > And the subsequent Writes will check if the channel is > free at the entry of send_pcc_cmd() anyway. > > However, for Read cmds, we need to wait for the cmd > completion bit to be flipped, since the actual Read > ops follow after returning from the send_pcc_cmd(). So, > only do the looping check at the end for Read ops. > > Also, instead of using udelay() calls, use ktime as a > means to check for deadlines. The current deadline udelay() is still there. Well, proposed approach in this patch is better than current code but I will be much more happy to see approach without delay()s under spin_lock if such approach exists. > in which the Remote should flip the cmd completion bit > is defined as N * Nominal latency. Where N is arbitrary > and large enough to work on slow emulators and Nominal > latency comes from the ACPI table (PCCT). This helps > in working around the CONFIG_HZ effects on udelay() > and also avoids needing different ACPI tables for Silicon > and Emulation platforms. What's the logic behind choosing N? Is it defined as 500 currently? Can it be some kind of configurable module or boot parameter? What if nominal latency given by firmware will be 100 mS? Frankly speaking, I personally expect that slow emulator is going to fail timing-sensitive activities and that's fine. Your requirement to use same tables for emulator and hardware is understandable too. > Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org> > Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> > --- > drivers/acpi/cppc_acpi.c | 102 ++++++++++++++++++++++++++++++++++------------- > 1 file changed, 74 insertions(+), 28 deletions(-) > > diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c > index 6730f96..36c3e4d 100644 > --- a/drivers/acpi/cppc_acpi.c > +++ b/drivers/acpi/cppc_acpi.c > @@ -39,6 +39,7 @@ > > #include <linux/cpufreq.h> > #include <linux/delay.h> > +#include <linux/ktime.h> > > #include <acpi/cppc_acpi.h> > /* > @@ -63,25 +64,56 @@ static struct mbox_chan *pcc_channel; > static void __iomem *pcc_comm_addr; > static u64 comm_base_addr; > static int pcc_subspace_idx = -1; > -static u16 pcc_cmd_delay; > static bool pcc_channel_acquired; > +static ktime_t deadline; > > /* > * Arbitrary Retries in case the remote processor is slow to respond > - * to PCC commands. > + * to PCC commands. Keeping it high enough to cover emulators where > + * the processors run painfully slow. > */ > #define NUM_RETRIES 500 > > +static int check_pcc_chan(void) > +{ > + int result = -EIO; > + struct acpi_pcct_shared_memory *generic_comm_base = > + (struct acpi_pcct_shared_memory *) pcc_comm_addr; > + ktime_t next_deadline = ktime_add(ktime_get(), deadline); > + int retries = 0; > + > + /* Retry in case the remote processor was too slow to catch up. */ > + while (!ktime_after(ktime_get(), next_deadline)) { > + if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { > + result = 0; > + break; > + } > + /* > + * Reducing the bus traffic in case this loop takes longer than > + * a few retries. > + */ > + udelay(3); > + retries++; Looks like retries variable is not used properly. You just increment it and that's all. Could you please check its usage or remove it? > + } > + > + return result; > +} > + > static int send_pcc_cmd(u16 cmd) > { > - int retries, result = -EIO; > - struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv; > + int ret = -EIO; > struct acpi_pcct_shared_memory *generic_comm_base = > (struct acpi_pcct_shared_memory *) pcc_comm_addr; > - u32 cmd_latency = pcct_ss->latency; > > - /* Min time OS should wait before sending next command. */ > - udelay(pcc_cmd_delay); > + /* > + * For CMD_WRITE we know for a fact the caller should have checked > + * the channel before writing to PCC space > + */ > + if (cmd == CMD_READ) { > + ret = check_pcc_chan(); > + if (ret) > + return ret; > + } For my eyes first pcc command to be called during booting is send_pcc_cmd(CMD_READ) from cppc_get_perf_caps(). That means we go to the loop inside check_pcc_chan() and to break that loop and successfully continue software expects bit PCC_CMD_COMPLETE to be set. I checked ACPI specs and didn't find any words about reset value of status register here. If it's there could you please point me to it and place comment here? Or you shouldn't rely on reset value of status reg (let's imagine that we rebooted kernel without informing firmware). I actually hit this bug when I started to test your patches. [snip] Anyway, I tested your patches and ready to give reviewed-and-tested-by after resolving current issues (and after re-testing). So, could you please keep me in c/c in next version? Thanks, Alexey. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Alexey, On 2/1/2016 12:38 PM, Alexey Klimov wrote: > Hi Prashanth and Ashwin, > > On Sat, Jan 23, 2016 at 1:07 AM, Prashanth Prakash <pprakash@codeaurora.org> wrote: >> From: Ashwin Chaugule <ashwin.chaugule@linaro.org> >> >> Previously the send_pcc_cmd() code checked if the >> PCC operation had completed before returning from >> the function. This check was performed regardless >> of the PCC op type (i.e. Read/Write). Knowing >> the type of cmd can be used to optimize the check >> and avoid needless waiting. e.g. with Write ops, >> the actual Writing is done before calling send_pcc_cmd(). >> And the subsequent Writes will check if the channel is >> free at the entry of send_pcc_cmd() anyway. >> >> However, for Read cmds, we need to wait for the cmd >> completion bit to be flipped, since the actual Read >> ops follow after returning from the send_pcc_cmd(). So, >> only do the looping check at the end for Read ops. >> >> Also, instead of using udelay() calls, use ktime as a >> means to check for deadlines. The current deadline > udelay() is still there. Well, proposed approach in this patch is better than > current code but I will be much more happy to see approach without delay()s under > spin_lock if such approach exists. udelay() is needed to avoid flooding the interconnects used while accessing the bits. While running tests, we wait for the bit to be set on a very small percentage of occasions. When it happens, it is mostly when there were requests going from different cores simultaneously, but I think we can handle it a little differently by batching requests rather than serializing. We are working on a patch to enable batching. I will post that patch set after a little more testing. Having said that, yes I agree with you it would be much nicer to get rid of usleep if possible. >> in which the Remote should flip the cmd completion bit >> is defined as N * Nominal latency. Where N is arbitrary >> and large enough to work on slow emulators and Nominal >> latency comes from the ACPI table (PCCT). This helps >> in working around the CONFIG_HZ effects on udelay() >> and also avoids needing different ACPI tables for Silicon >> and Emulation platforms. > What's the logic behind choosing N? Is it defined as 500 currently? > Can it be some kind of configurable module or boot parameter? > What if nominal latency given by firmware will be 100 mS? > > Frankly speaking, I personally expect that slow emulator is going to fail > timing-sensitive activities and that's fine. > Your requirement to use same tables for emulator and hardware is understandable > too. 500 was arbitrarily chosen to make sure emulation would not fail. I suppose it is cleaner to remove the retries after some profiling/testing to make sure we are not relying on retries on actual hardware as well. I can run some testing and address this as part of different patch-set. >> + /* Retry in case the remote processor was too slow to catch up. */ >> + while (!ktime_after(ktime_get(), next_deadline)) { >> + if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { >> + result = 0; >> + break; >> + } >> + /* >> + * Reducing the bus traffic in case this loop takes longer than >> + * a few retries. >> + */ >> + udelay(3); >> + retries++; > Looks like retries variable is not used properly. You just increment it and that's all. > Could you please check its usage or remove it? Yes, retries variable is not necessary. I will remove it in next version. >> static int send_pcc_cmd(u16 cmd) >> { >> - int retries, result = -EIO; >> - struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv; >> + int ret = -EIO; >> struct acpi_pcct_shared_memory *generic_comm_base = >> (struct acpi_pcct_shared_memory *) pcc_comm_addr; >> - u32 cmd_latency = pcct_ss->latency; >> >> - /* Min time OS should wait before sending next command. */ >> - udelay(pcc_cmd_delay); >> + /* >> + * For CMD_WRITE we know for a fact the caller should have checked >> + * the channel before writing to PCC space >> + */ >> + if (cmd == CMD_READ) { >> + ret = check_pcc_chan(); >> + if (ret) >> + return ret; >> + } > For my eyes first pcc command to be called during booting is send_pcc_cmd(CMD_READ) > from cppc_get_perf_caps(). That means we go to the loop inside check_pcc_chan() and > to break that loop and successfully continue software expects bit PCC_CMD_COMPLETE to be > set. > I checked ACPI specs and didn't find any words about reset value of status register here. > If it's there could you please point me to it and place comment here? Or you shouldn't rely > on reset value of status reg (let's imagine that we rebooted kernel without informing firmware). > I actually hit this bug when I started to test your patches. The specification does mention the following in the Doorbell Protocol (section 14.3 in 6.0 spec) "To ensure consistency of the shared memory region, the shared memory region is exclusively owned by OSPM or the platform at any point in time. After being initialized by the platform, the region is owned by OSPM. Writing..." Given the above, it is fair to think that the platform will initialize the command completion bit accordingly. If platform wants to prevent the OSPM from accessing region during init, it can set this bit accordingly to achieve the same. > > [snip] > > > Anyway, I tested your patches and ready to give reviewed-and-tested-by after resolving current issues > (and after re-testing). So, could you please keep me in c/c in next version? Sure, I will keep in cc. Thanks for reviewing the code and providing inputs! > > Thanks, > Alexey. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-acpi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 6730f96..36c3e4d 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -39,6 +39,7 @@ #include <linux/cpufreq.h> #include <linux/delay.h> +#include <linux/ktime.h> #include <acpi/cppc_acpi.h> /* @@ -63,25 +64,56 @@ static struct mbox_chan *pcc_channel; static void __iomem *pcc_comm_addr; static u64 comm_base_addr; static int pcc_subspace_idx = -1; -static u16 pcc_cmd_delay; static bool pcc_channel_acquired; +static ktime_t deadline; /* * Arbitrary Retries in case the remote processor is slow to respond - * to PCC commands. + * to PCC commands. Keeping it high enough to cover emulators where + * the processors run painfully slow. */ #define NUM_RETRIES 500 +static int check_pcc_chan(void) +{ + int result = -EIO; + struct acpi_pcct_shared_memory *generic_comm_base = + (struct acpi_pcct_shared_memory *) pcc_comm_addr; + ktime_t next_deadline = ktime_add(ktime_get(), deadline); + int retries = 0; + + /* Retry in case the remote processor was too slow to catch up. */ + while (!ktime_after(ktime_get(), next_deadline)) { + if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { + result = 0; + break; + } + /* + * Reducing the bus traffic in case this loop takes longer than + * a few retries. + */ + udelay(3); + retries++; + } + + return result; +} + static int send_pcc_cmd(u16 cmd) { - int retries, result = -EIO; - struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv; + int ret = -EIO; struct acpi_pcct_shared_memory *generic_comm_base = (struct acpi_pcct_shared_memory *) pcc_comm_addr; - u32 cmd_latency = pcct_ss->latency; - /* Min time OS should wait before sending next command. */ - udelay(pcc_cmd_delay); + /* + * For CMD_WRITE we know for a fact the caller should have checked + * the channel before writing to PCC space + */ + if (cmd == CMD_READ) { + ret = check_pcc_chan(); + if (ret) + return ret; + } /* Write to the shared comm region. */ writew(cmd, &generic_comm_base->command); @@ -90,26 +122,25 @@ static int send_pcc_cmd(u16 cmd) writew(0, &generic_comm_base->status); /* Ring doorbell */ - result = mbox_send_message(pcc_channel, &cmd); - if (result < 0) { + ret = mbox_send_message(pcc_channel, &cmd); + if (ret < 0) { pr_err("Err sending PCC mbox message. cmd:%d, ret:%d\n", - cmd, result); - return result; + cmd, ret); + return ret; } - /* Wait for a nominal time to let platform process command. */ - udelay(cmd_latency); - - /* Retry in case the remote processor was too slow to catch up. */ - for (retries = NUM_RETRIES; retries > 0; retries--) { - if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) { - result = 0; - break; - } - } + /* + * For READs we need to ensure the cmd completed to ensure + * the ensuing read()s can proceed. For WRITEs we dont care + * because the actual write()s are done before coming here + * and the next READ or WRITE will check if the channel + * is busy/free at the entry of this call. + */ + if (cmd == CMD_READ) + ret = check_pcc_chan(); - mbox_client_txdone(pcc_channel, result); - return result; + mbox_client_txdone(pcc_channel, ret); + return ret; } static void cppc_chan_tx_done(struct mbox_client *cl, void *msg, int ret) @@ -306,6 +337,7 @@ static int register_pcc_channel(int pcc_subspace_idx) { struct acpi_pcct_hw_reduced *cppc_ss; unsigned int len; + u64 usecs_lat; if (pcc_subspace_idx >= 0) { pcc_channel = pcc_mbox_request_channel(&cppc_mbox_cl, @@ -335,7 +367,14 @@ static int register_pcc_channel(int pcc_subspace_idx) */ comm_base_addr = cppc_ss->base_address; len = cppc_ss->length; - pcc_cmd_delay = cppc_ss->min_turnaround_time; + + /* + * cppc_ss->latency is just a Nominal value. In reality + * the remote processor could be much slower to reply. + * So add an arbitrary amount of wait on top of Nominal. + */ + usecs_lat = NUM_RETRIES * cppc_ss->latency; + deadline = ns_to_ktime(usecs_lat * NSEC_PER_USEC); pcc_comm_addr = acpi_os_ioremap(comm_base_addr, len); if (!pcc_comm_addr) { @@ -604,7 +643,7 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps) (ref_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) || (nom_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) { /* Ring doorbell once to update PCC subspace */ - if (send_pcc_cmd(CMD_READ)) { + if (send_pcc_cmd(CMD_READ) < 0) { ret = -EIO; goto out_err; } @@ -662,7 +701,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs) if ((delivered_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) || (reference_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) { /* Ring doorbell once to update PCC subspace */ - if (send_pcc_cmd(CMD_READ)) { + if (send_pcc_cmd(CMD_READ) < 0) { ret = -EIO; goto out_err; } @@ -713,6 +752,13 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) spin_lock(&pcc_lock); + /* If this is PCC reg, check if channel is free before writing */ + if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) { + ret = check_pcc_chan(); + if (ret) + goto busy_channel; + } + /* * Skip writing MIN/MAX until Linux knows how to come up with * useful values. @@ -722,10 +768,10 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) /* Is this a PCC reg ?*/ if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) { /* Ring doorbell so Remote can get our perf request. */ - if (send_pcc_cmd(CMD_WRITE)) + if (send_pcc_cmd(CMD_WRITE) < 0) ret = -EIO; } - +busy_channel: spin_unlock(&pcc_lock); return ret;